Digital Surge/ DCHipot Tester

Transcription

1 B AKER INSTRUMENT COMPANY Digital Surge/ DCHipot Tester D6000/12000 & DS206/212 User s Manual rev C BAKER INSTRUMENT COMPANY PO Box 587 Fort Collins, Colorado (970) FAX (970) Toll-free (800)

2 BAKER INSTRUMENT COMPANY User s Manual Models D6000/12000 & DS206/212 Baker Instrument Company 4812 McMurry Avenue, Suite 100 Fort Collins, CO (FAX) (USA Only) Information furnished in this manual by Baker Instrument Company is believed to be accurate and reliable. However, Baker Instrument Company assumes no responsibility for the use of such information nor for any infringements of patents or other rights of third parties that may result from its use. No license is granted by implication or otherwise under any patent rights of Baker Instrument Company. WARNING: Baker Instrument Company assumes no liability for damages consequent to the use of this product. No part of this document may be reproduced in part or in full by any means such as photocopying, photographs, electronic recording, videotaping, facsimile, etc., without written permission from Baker Instrument Company, Fort Collins, Colorado. Copyright July 1999, Baker Instrument Company, 4812 McMurry Ave., Suite 100, Fort Collins, CO DOC# User s Manual Rev. C(13)-7/99

3 User s Manual Rev. C(13)-7/99

4 Table of Contents Preface Safety Precautions i Operation Notes ii Terms and Symbols ii Warranty Notes iii Technical Specifications iv Section 1: Introduction Principles of DC High-Potential (Hipot) Testing The Principles of Surge Testing Surge Comparison Testing Section 2: Unit Controls Front Panel Control Functions Tester Display Section 3: Storage and Print Capabilities STORE RECALL PRINT CLEAR Section 4: Test Procedures and Voltages General User Cautions and Notes Initial Tester Power-Up and Check-Out Recommended Voltages Section 5: DC Hipot Test Understanding Hipot Testing The Hipot Test Display DC Hipot Test and Set-Up DC Hipot Over-Current Trip DC Hipot Application Tips Resistance Temperature Compensation User s Manual Rev. C(7)-7/99

5 Table of Contents Section 6: Surge Testing User s Manual Rev. C(7)-7/99 The Surge Test Display Single Coil Surge Test and Set-Up Three Phase Motor Surge Test and Set-Up Surge Voltage Measurement Factors Affecting the Surge Tester s Output Notes for Surge and Surge Comparison Tests Determination of a Fault Good, Stable Trace Instability Separation When Compared to Another Wave Pattern Open Circuit Grounded Winding Section 7: Surge Test Applications Maintenance Testing Application Notes Single Phase Motors and Two Terminal Devices Form Coils Notes and Tips for Form Coils Three Phase Motors Two or More Single Coils Notes and Precautions for Two Single Coils Wound Rotor Motors Synchronous Motor/Generator Chiller Motor Testing Field Coils DC Motor/Generators Armatures Bar-to-Bar Surge Test Span Testing Notes and Tips for Span Testing Armatures Testing Large AC Stators/Motors Notes and Tips for Large AC Stator/Motors Rotor Loading (Coupling) when Testing Assembled Motors Testing Assembled Motors from the Switchgear Note and Tips for Testing from the Switchgear Transformers Single Phase Transformers Three Phase Transformers Section 8: Additional Tests Polarization Index Test Polarization Index Procedure Polarization Index Evaluation Step-Voltage Test

6 Table of Contents Appendix A: Typical Winding Faults Appendix B: Troubleshooting Self Help and Diagnostics B-1 Applications: What to Do First! B-2 Common Application Problems B-2 Service: What to Do First! B-4 Printer Check B-4 Open Condition Display B-4 Hipot Display Checks B-4 Hipot Trip Check B-5 Open Ground Check B-5 Limited Output Surge Waveform B-6 Precautions for Proper Operation B-6 Service Manual B-6 Warranty Return B-6 WARRANTY RETURN FORM B-7 Appendix C: Calibration Introduction C-1 Surge Calibration Procedure C-2 Equipment Required C-2 Set-Up C-2 Hipot Calibration Procedure C-4 Equipment Required C-4 Set-Up C-4 Special Hipot Notes C-5 Hipot Adjustments C-5 Appendix D: PP130/PP230 Power Pack Caution Notes D-1 Emergency Shut-Off Button D-2 Initial Set-Up D-2 Power Pack Operation D-3 Surge Testing D-3 DC Hipot Testing D-4 Lead Connections D-6 Note Regarding 220/240 VAC Units D-6 User s Manual Rev. C(7)-7/99

7 Table of Contents Appendix E: Model AT101D Bar-to-Bar Armature Accessory Operation E-2 Determination of a Fault E-4 Application Recommendations E-5 Specifications for the AT101D Bar-to-Bar Armature Testing Accessory..... E-5 AT101D Calibration Procedure E-6 Appendix F: Digital Tester Firmware Index Operation F-1 Hardware Block Diagrams F-3 User s Manual Rev. C(7)-7/99

8 Preface Safety Precautions NOTE: The general safety information presented here is for both operating and service personnel. Specific warnings and cautions will be found throughout this manual where they apply. DANGER High-voltage test equipment should be handled with CAUTION. High-voltage test procedures should be followed, including use of high voltage gloves! Do NOT touch the test leads, winding or component under test while a test is being performed. Severe electric shock may result. Never attempt a two-party operation. Always know what test is being performed and when. Never attempt to test an energized motor. Be sure the surge test instrument is grounded. Use a three lead grounded supply (or an extra ground lead if unsure of supply ground). For capacitor start motors or systems with surge arrestors/power factor capacitors, be sure to disconnect all capacitors from the test circuit before testing. The surge tester is NOT approved for use in an explosive environment. Upon completion of a DC High Potential test, short the winding, motor, etc., to ground and allow time for discharge before disconnecting the test leads. Ensure the tester leads are disconnected before the motor is energized or powered up. Do not operate in an explosive environment. Do not remove the product covers or panels or operate the tester without the covers and panels properly installed. WARNING: Operation of the tester by persons who are using a pacemaker may present unusual safety risks. Such persons should take special precautions! User s Manual i Rev. C(3)-7/99

9 Preface Power Source Precautions Operation Notes This product is intended to operate from a power source that does not apply more than nominal 120 volts RMS (D6000/12000) or nominal 240 volts RMS (DS206/212) between the supply conductor or between either supply conductor and ground. A protective ground connection by way of the grounding conductor in the power cord is essential for safe operation. Ground the Product This product is grounded through the grounding conductor of the power cord. To avoid electrical shock, plug the power cord into a properly wired receptacle before connecting the product test leads. Danger from Loss of Ground Upon loss of the protective ground connection, all accessible conductive parts, including knobs and controls that may appear to be insulated, can render an electric shock! Irregularities, particularly vertical peaks, may be seen in the first cycle of the wave pattern. These occur most frequently on large, high voltage motors. Do not interpret these as faults in the winding. Any winding fault will be seen through the entire wave pattern. Do not change the TEST LEAD SELECT, if so equipped, switch setting during a test. When increasing the applied voltage, switch to a higher VOLTS/DIV setting so the entire wave pattern remains visible on the display. Always return the OUTPUT VOLTAGE control to MIN when a test is complete. Begin each test at a the MIN voltage setting. Failure to do so may result in damage to the test winding and/or the tester. Terms and Symbols ii User s Manual Rev. C(3)-7/99 CAUTION statements identify conditions or practices that could result in damage to the equipment or other property. WARNING statements identify conditions or practices that could result in personal injury or loss of life. This symbol indicates cautionary information. This symbol indicates warning information. Protective ground earth lead.

10 Preface Warranty Notes Important Notice Concerning the Warranty and Repairs Training Seminars The warranty is VOID if the tester is shipped in any container other than the original container it was shipped in OR factory specified packaging. For replacement factory specified packaging and instructions for proper shipment of the tester see Shipment on page v. Also, be sure to complete the WARRANTY RETURN FORM on page B-7 when sending your tester to Baker Instrument Company. If there is a failure of the Baker tester, regardless of whether it is under warranty or not, the customer should CALL the Baker Instrument Company Service Department BEFORE returning the unit for repair. In some cases, the repair may be done by the customer at a significant savings. If under warranty, the customer may still save costly shipping charges and lost time while the unit is being shipped and repaired. Our service staff may also direct the customer to ship the unit to one of our Authorized Service Centers for repairs. When calling the Baker Service Department or one of the Service Centers, please have the MODEL and SERIAL NUMBERS (located on the rear panel of the unit) available. If the unit is out of warranty, a purchase order will be required if the unit is returned for repair. The Baker Instrument Company Service Department phone number is or (970) Please Take A Moment... Now that you own a Baker Instrument Company Digital Tester, allow us to support your operation and maintenance needs. Please take a few minutes to fill out and return the yellow postage-paid registration card found in the beginning of this manual. Extensive training seminars are conducted by Baker Instrument Company to help you get the most out of the Surge/Hipot Tester in a wide variety of applications. In-House Seminars are available at your site. In these seminars, you can tailor the training for your specific needs. Please contact the Sales Department at Baker Instrument Company, or (970) , to schedule an In- House Seminar. User s Manual iii Rev. C(3)-7/99

11 Preface Technical Specifications (This information conforms to the requirements of MIL-M-7298D) Surge Test Model D6000/DS206 Model D12000/DS212 Output Voltage: 0-6,000 volts 0-12,000 volts Max Output Current: 380 amps 800 amps Pulse Energy: 0.72 joules 2.88 joules Sweep Range: µ-seconds (same) Volts/Division: 500/1000/2000/3000 (same) Repetition Rate: 5 Hz 5 Hz Voltage Measurement Accuracy: +/- 5% (same) DC High Potential (Hipot) Test Output Voltage: 0-6,000 volts 0-12,000 volts Max Output Current: 1000 µ-amps (same) Current Resolution: 1/10/100 µ-amps/division (same) Over-current Trip Settings: 10/100/100 µ-amps (same) Voltage and Current Measurement Accuracy: +/- 5% (same) Meg-Ohm Accuracy: +/- 5% (same) Max Meg-Ohm Reading: 20,000 MΩ (same) Physical Characteristics Power and Utility Weight: 50 pounds 58 pounds 22.2 kilograms 25.0 kilograms Dimensions (W x H x D): 21 x 9 x 19 inches 21 x 9 x 19 inches 560 x 210 x 480 mm 560 x 210 x 480 mm Power Requirements: D6000:120 VAC/60 Hz/ D12000:120 VAC/60 Hz/ 118 Watts 350 Watts DS206:220 VAC/50 Hz/ DS212: 220 VAC/50 Hz/ 118 Watts 350 Watts Input power must be 110 to 120 VAC at 60 Hz for the D6000/12000 or 220 to 230 VAC at 50 Hz (single-phase source only) for the DS206/212. Please be aware that fluctuations in input voltage will affect output voltages. iv User s Manual Rev. C(3)-7/99

12 Preface Environmental The tester should only be operated in temperatures ranging from 0 to 100 degrees Fahrenheit (-17.8 to 37.8 degrees Celsius). As with all insulation dielectric and resistivity measurements, humidity will affect the condition of the instrument s components over time. Relative humidity of the storage environment should be less than 50 percent. This instrument is NOT water-proof or sealed against water entry. This tester is NOT approved for use in an explosive environment. Storage (Indoor/Outdoor) Shipment This instrument should not be stored in any location where water entry to the instrument could occur. Also, humidity will affect the operation of the instrument. All Baker testers are shipped using factory foam-filled containers. Should the tester need to be returned to Baker Instrument Company for any reason, we recommend using the original packaging the unit came in or the following factory specified packaging: For the D Series Tester order P/N RP6/12S/DBAMF Contact Baker Instrument Company to order factory specified packaging for your tester. List of Items Furnished 1 each Surge tester with attached test leads 1 each Removable line power cord 1 each Instruction manual User s Manual v Rev. C(3)-7/99

13 Preface vi User s Manual Rev. C(3)-7/99

14 Section 1 Introduction The Digital Surge/Hipot Tester is the newest tester offered by Baker Instrument Company s Standard Product Division. The Digital Tester is available in both 6and 12 kv models. Each unit is capable of supporting the application of the AT101 Bar-to-Bar Armature Tester or the 30 kv Power Pack accessory unit. Versatility in testing is enhanced in the Digital Tester with its capability to internally store, recall, and summarize test measurements. A parallel port is provided to connect the tester to a printer or to a personal computer for test acquisition. The Digital Tester is designed to directly interface with Baker Instrument Company s Motor Test Acquisition (MTA 5.0) database software. Principles of DC High-Potential (Hipot) Testing DC Hipot Testing has proved to be a useful tool to non-destructively evaluate the dielectric strength of ground insulation. No insulation is perfect and all have some conductivity, so some current flows or leaks along or through the insulation to ground. By charging the winding to a specific test voltage and holding the frame at ground, leakage currents can be monitored. The insulation s resistance is an important factor in evaluating its condition. However, insulation resistance is only one factor. It has little to do with insulation s dielectric strength or breakover voltage. Insulation resistance can be measured and dielectric strength assured with a DC Hipot Test. The resistance is determined by dividing the voltage impressed on the coil by the leakage current measured. Both are monitored with the DC Hipot test. Determining resistance via voltage impressed and leakage current can be understood with the analogy of a water pipe. Two tests of the pipe are possible. Imagine a water pipe which has no leaks and is capable of withstanding a maximum pressure. If a small hole is drilled in the pipe, a certain amount of water would escape and cause leakage. An increase in water pressure in the pipe would cause a measurable increase in the leakage of water, but it would not necessarily rupture the pipe. In the second test, if a pipe with no holes were worn thin and the pressure increased to test the pipe s strength, at some pressure it may rupture, allowing all the water to be released. In an electrical conductor, the pipe would be an insulator and the water pressure would be the voltage impressed on it. Leakage current in the insulator would be comparable to water flowing through the hole in the pipe. As voltage is increased on the leaking insulator there would be a corresponding increase in leakage Do not touch test leads while test is in progress! User s Manual 1-1 Rev. C(11)-7/99

15 Introduction current. Higher leakage currents (a larger hole in the pipe) correspond to lower resistance of the insulation to the flow of current. A perfect insulator (pipe with no holes) is said to have high resistance. The second test, where the pipe is subjected to rupturing, is comparable to measuring the dielectric strength or dielectric limit of the insulation. The possibility of rupturing is measured in an electrical conductor with a high potential (Hipot) test. The point of rupture is called the dielectric limit of the insulation material. In Hipot Testing, the voltage (water pressure on the pipe) is increased on the coil. However, the DC Hipot test does not breakdown the insulation. Good insulation has a dielectric strength value much higher than the operating voltage of the apparatus and common field test voltages.the Hipot Test is used to ensure that the insulation DOES NOT breakdown or rupture at a prescribed test value. The test voltage should be less than the rated dielectric strength of the insulation. If the insulation does fail under the test, the insulation to ground is unreliable and the apparatus is unusable. Knowledge of the real behavior of resistors, not just ideal resistors, will help the operator to test the winding insulation to a point before the insulation is broken down. Current Low or Poor Resistance Typical Real-World Resistance Good Resistance Current Detail of Typical Resistance A marked upward change may predict insulation breakdown. Insulation Breakdown Voltage Voltage For an ideal resistor, good or poor, as the voltage is increased, the leakage current will increase proportionately and indefinitely (left figure above). However, insulation resistance in the real world rarely behaves in this manner. Instead, the current in a typical resistor will increase proportionately with voltage until the voltage is within as little as 5% of the breakdown voltage. Just before insulation breakdown, the current will rise faster than the voltage. At still higher voltage, the insulation will completely break down and the current will rise extremely fast (right figure above). The key to DC Hipot testing is to look for leakage current that is rising faster than the increase in voltage that is applied to the winding. The test can then be stopped before the insulation is damaged. (For more information on DC Hipot tests refer to IEEE which describes test procedures, voltages, safety, and interpretation.) 1-2 User s Manual Do not touch test leads while test is in progress! Rev. C(11)-7/99

16 Introduction The Principles of Surge Testing Prior to the introduction of surge testing, the most common electrical test for motors was a low-potential test of the winding insulation to ground (or frame). This popular test is the Insulation Resistance or MegOhm test. This test is adequate for testing winding insulation to ground, but it does not detect failures between turns and phases. A more thorough test is the Surge Test. A typical motor coil consists of copper wire turns or windings. Motor winding insulation failure often starts as a turn-toturn, copper-to-copper, or winding-to-winding fault. Surge Tests can detect the early stages of insulation failures in the winding such as coil-to-coil failures, short circuits, grounds, misconnections, and wrong turns counts. Brief voltage surges (or pulses) are applied to the coil during a Surge Test to create a voltage gradient (or potential) across the length of the wire in the winding. This gradient produces a momentary voltage stress between turns. The coil will respond, in the time periods between pulses, with a ringing or damped sinusoidal waveform pattern. Each coil has it s own unique signature ringing or wave pattern which can be displayed on a CRT display screen. Example of a ringing wave pattern resulting from Surge Testing The wave pattern observed during a Surge Test is directly related to the coil s inductance. (There are other factors influencing the wave pattern but inductance is the primary one.) The coil becomes one of two elements in what is known as a tank circuit an LC-type circuit made up of the coil s inductance (L) and the surge tester s internal capacitance (C). Inductance (L) of a coil is basically set by the number of turns in a winding and the type of iron core it rests. When inductance decreases, the frequency of the wave pattern will increase according to the formula 1 Frequency = π LC A surge test can detect a fault between turns that is due to weak insulation. If the voltage potential is greater than the dielectric strength of the turn insulation, one or more turns may be shorted out of the circuit. In effect, the number of turns in the coil is reduced. Fewer working turns reduces the inductance of the coil and increases the frequency of the ringing pattern from the surge. Do not touch test leads while test is in progress! User s Manual 1-3 Rev. C(11)-7/99

17 Introduction The voltage or amplitude of the surge wave pattern is also reduced due to the decrease in inductance of coil with a fault between turns. It is determined by the formula Voltage = L---- di, where the current (i) varies according the to pulse time (t). dt When the insulation between turns is weak, the result is a low energy arc-over and a change in inductance. When this happens the wave pattern becomes unstable it may shift rapidly to the left and right, and back to the original position. A reduction in inductance occurs due to turn-to-turn faults, phase-to-phase faults, misconnections, open connections, etc. Partial ground wall testing is also performed in asurge test when there is a ground line to the machine frame. The Surge Test is most often used to test turn-to-turn insulation of coils or single windings. Form coils, start and run windings, and multi-tapped windings are a few examples. Surge Tests are also used to compare new windings to a standard winding to assure they conform. Surge Comparison Testing The results of Surge Tests can be used to compare individual motors or windings in order to detect faults. This is Surge Comparison Testing. Because the wave pattern of a Surge Test is unique to the coil being tested (due to its unique number of turns, type of wire and insulation, orientation, etc.), wave patterns of supposedly identical coils should also be identical. Any difference in the coil (more or less turns, insulation break-down, orientation, etc.) would result in a different wave pattern during the Surge Test. These differences are most often due to a fault in the winding. Three-phase motors provide an illustration of Surge Comparison Testing. A typical three-phase motor is assumed to be made of three identical coils or phases. Therefore, the results of three equal Surge Tests on each phase of the motor should also be identical. If there are any differences in the three results, one or more of the phases contains a fault. The Digital Tester provides a means for observing very small differences in Surge Tests, making it very sensitive to any faults in the windings. The tester does this by simultaneously displaying the wave patterns of two Surge Tests. When the wave patterns of two equal voltage Surge Tests are displayed simultaneously, if a single wave pattern is seen, the phases being tested are equal in their inductance. In other words the phases or windings have the same number of turns, insulation, orientation, etc. and are considered to be good. 1-4 User s Manual Do not touch test leads while test is in progress! Rev. C(11)-7/99

18 Introduction When the wave patterns of two equal voltage Surge Tests are displayed simultaneously, if two distinct wave patterns are seen, the phases being tested are NOT equal in their inductance. There probably is a fault in one of the windings or there is some other cause for the differing inductance. For example, the faulted winding may have shorted turns compared to the complete phase, reducing the inductance, and thus altering the wave pattern. The Comparison Test detects any differences in the coils by comparing each winding to the other windings. In a three phase motor, if one phase is different than the others, there will be at least two different Surge Test wave patterns. An example of Comparison Testing can be applied to newly manufactured or rewound motors which may contain an occasional error in the winding turns count. If the error is more turns placed in one phase, the inductance becomes greater and frequency of the wave pattern becomes lower. The results of a Surge Test of the new faulty motor would be compared to the Surge Test of a standard motor which is known to have the correct number of turns. The difference in winding turns will be evident because the wave patterns will differ. Examples of Surge Comparison Testing Surge comparison testing is most easily applied and understood by using a stator from a three phase, lap wound induction motor as an example. When all three phases in a good motor are wound identically, comparing the phases will show the same single wave pattern. STORE RECALL PRINT RECALL Record 1 Lead V/div 2 us/div CLEAR Peak: 1500 V Pulse: V/div SURGE 2 us/div Good Comparison Pattern: Only one wave appears on the surge tester screen when two tests are diplayed simultaneously. (The wave patterns being compared superimpose exactly.) Do not touch test leads while test is in progress! User s Manual 1-5 Rev. C(11)-7/99

19 Introduction When one of the phases has a fault, one of two things will be seen on the tester. (Refer to the figures that follow.) The wave pattern may become erratic during the test, indicating intermittent shorting in the winding and arc-over (the left example below). The wave pattern for the faulted phase may appear stable, but when it is compared to the wave pattern of another good phase, it will be slightly different in comparison (the right example below). This is indicative of a fault in the phase associated with the differing wave pattern. Usually, this wave pattern is decreased in amplitude and has a higher frequency which shifts it toward the left. STORE RECALL PRINT CLEAR CLEAR STORE RECALL PRINT RECALL Record 1 Lead V/div 2 us/div Peak: 1500 V Pulse: 45 Faulty Peak: 1500 V Pulse: 45 Display rapidly shifts between wave patterns Good 500 V/div SURGE 2 us/div 500 V/div SURGE 2 us/div Faulty Surge Patterns: Waveforms are erratic during the test (left) or separated throughout the entire trace when they have been stored and recalled (right). NOTE: Intermittent shorting in the winding or arc-over will not be obvious when the wave pattern has been stored. The kinetic action of shorting or arcover can only be seen during live testing. The digital tester is capable of displaying only one live wave pattern at a time. During intermittent shorting or arc-over, the tester will display either the wave pattern of the good coil with the correct number of turns or the shorted coil, with the effectively reduced number of turns due to the short. In some cases, the shifts between the two or more patterns may be so rapid that, to the eye, it will appear as though there are two or more wave patterns on the display. 1-6 User s Manual Do not touch test leads while test is in progress! Rev. C(11)-7/99

20 Section 2 Unit Controls Front Panel Control Functions NOTE: The numbers in parentheses ( ) below correspond to the diagram above. (1) PRINTER port (2) AUX port (3) LINE IN Parallel port for printing waveforms and summaries displayed by the Digital Tester This port may also be used for interfacing with the Motor Test Acquisition (MTA 5.0 or higher) program on a personal computer. Auxiliary port for using the Digital Tester with a 30 kv power pack, for high voltage testing, or the AT101 armature tester. (Refer to Appendix D: PP130/PP230 Power Pack and Appendix E: Model AT101D Bar-to-Bar Armature Test Accessory respectively.) The external AC power supply plug wire is inserted here. Do not touch test leads while test is in progress! User s Manual 2-1 Rev. C(11)-7/99

21 Unit Controls (4) ON/OFF (5) Function Keys The power ON/OFF switch contains a circuit breaker and a green ON indicator lamp. Function keys for data collection, recall, and printing of tests. The keys correspond to choices provided on the CRT display below them. See Section 3: Storage and Print Capabilities, for a detailed description of the tester s storage capabilities. (6) Digital Cathode Ray Tube (CRT) The Digital Cathode Ray Tube (CRT) is the location where information programed into and gathered by the tester are displayed. At the top, menus corresponding to the four function keys above the CRT are shown. The main portion of the screen displays the waveforms being measured and/or recalled with corresponding graticules for reference. The bottom portion shows the volts/division for the waveform, the name of the test on display, and micro-seconds/division (microamps/division for hipot tests). Refer to Tester Display on page 2-6. When using thefunction keys, the screen will display options pertinent to the storage, recall, and print capacities of the unit. Refer to Section 3: Storage and Print Capabilities. Error messages are also displayed here. (7) OPEN GROUND warning light When the AC line source is not properly grounded, the red Open Ground light will illuminate. The test set will power up, but high-voltage will be held inoperative by theinternal electronics (see Appendix B: Troubleshooting, for additional information). (8) HIPOT TRIP warning light (9) INTENSITY This lamp illuminates to indicate the DC Hipot trip circuit has stopped the test. The red lamp will stay illuminated until the TEST (17) button is released. Rotation of this control will adjust the intensity or brightness of the display. Clockwise (CW) will increase intensity. Counterclockwise (CCW) will decrease intensity. Intensity has a slight effect on the focus and can be adjusted toa blank screen. (10) VERTICAL POSITION This control adjusts the up or down positioning of the surge wave pattern. Optimum positioning is usually on center or one major graticule line below center for surge testing. 2-2 User s Manual Do not touch test leads while test is in progress! Rev. C(11)-7/99

22 Unit Controls (11) HORIZONTAL POSITION This control adjusts the side-to-side positioning of the surge wave pattern. A trace beginning at the far left is suggested for surge testing. (12) FUNCTION selector (13) VOLTS/DIV This control selects the type of test to be performed and the sensitivity of the DC Hipot leakage current display. The name of the test chosen is displayed on the lower portion of the CRT for reference. There are four primary positions as follows: AT101: This position is used when using the Baker Instrument Company Model AT101 Bar-to-Bar Armature Testing Accessory. Note: The Zero Start Interlock is disabled when this function is selected and the FOOTSWTICH (19) is depressed. AUX: The auxiliary position is for use with a 30 kv Power Pack (refer to Appendix D: PP130/PP230 Power Pack). The display will also show wave patterns from accessory units in this position. SURGE: This position selects the Surge Test. The name of the test and microseconds per division measured is displayed on the lower portion of the CRT for reference. A digital readout for the peak voltage of the test is also displayed in the upper right portion of the screen for reference. HIPOT µ-amps/div: This position is used for DC Hipot testing. The name of the test is displayed on the lower portion of the CRT for reference. A digital readout for the leakage current (in microamps) of the test and the resultant resistance in mega ohms is displayed on the screen for reference. There are three positions associated with the Hipot test. The three positions are 100, 10, and 1 micro amps per division. The chosen micro amps per division setting is displayed on the lower right portion of the CRT for reference during testing. µ-amps/div controls the sensitivity of the current displayed. It also automatically selects the auto-ranging overcurrent trip point which will be ten times these settings or 1000, 100, and 10 micro-amps respectively. This control sets the sensitivity of the display or scale factor in volts per division for both the Surge and DC Hipot test trace. There are four settings corresponding to, from right to left, 500, 1000, 2000, and 3000 volts per division. The volts per division setting chosen is displayed on the lower left portion of the CRT. NOTE: This control does not affect or limit the output voltage of the tester! Do not touch test leads while test is in progress! User s Manual 2-3 Rev. C(11)-7/99

23 Unit Controls (14) SECONDS/DIV This control adjusts the seconds per division, or sweep rate, of the trace on the display. There are ten settings corresponding to, from left to right, 2, 6, 10, 20, 60, 100, 200, 500, 1000, and 2000 micro-seconds per division. The seconds per division setting chosen is displayed on the lower right portion of the display for reference during Surge Testing. This is the trace time duration taken to display the pattern. This control will have the effect of expanding or contracting the wave pattern when surge testing. CAUTION For the surge test, with the SECONDS/DIV control at the lowest possible setting, the ringing pattern must be at least one division in length for one full cycle. Less than one division for the first cycle indicates a very low inductive load. DAMAGE to the instrument is possible when operated more than ten (10) seconds into a low inductive load. (15) LEADS ENERGIZED indicator light The indicator will light when voltage is applied during a test. (16) OUTPUT CONTROL This control adjusts the output voltage of the tester. Clockwise (CW) rotation increases output and counterclockwise (CCW) rotation decreases output. Full CCW is the MIN point or zero output and full CW is MAX or 100% of the unit s rated output. A Zero Start Interlock is connected to the output control for use during Surge and Hipot testing. The user must return the output control to MIN each time before pressing the TEST button (17). In other words, if the TEST button is pressed while the OUTPUT control is above zero the instrument s output is disabled until the OUTPUT control is rotated to MIN. The Zero Start Interlock is disabled for AT101 testing. CAUTION When testing a highly inductive coil (high turns counts), it is possible to develop voltages in excess of the unit s rated output. Damage may occur to the instrument. Use caution to limit the output to no more than the instrument s rating. Monitor the voltage by observing the digital readout on the CRT display. 2-4 User s Manual Do not touch test leads while test is in progress! Rev. C(11)-7/99

24 Unit Controls (17) TEST button The TEST button activates the high voltage output of the tester. One of theselected modes, Surge or Hipot, will be enabled and a voltage will be impressed on the device being tested. This button automatically disengages when released. (18) TEST Lead SELECT (TLS) Test Lead Connections This is a high-voltage rotary switch that selects which test lead will be HOT or energized, which are OPEN during Hipot tests, and which are to be at GROUND. Settings 1 2 and 3 are for Surge Testing. The RED Test Leads (20) are numbered and correspond to these settings. The lead number setting indicates which test lead is HOTor energized. The HIPOT position energizes test lead #1 and opens test leads #2 and #3. The LEADS GROUND position holds all three red leads at the same grounded potential as the black GROUND lead. It is a safety feature that should always be used whenever the operator touches the tester s leads to change their position. This position also deactivates the Zero Start Interlock which prevents high-voltage generation. Refer to the chart below as a reference for TLS positions and lead potential. SWITCH POSITION Test Lead #1 Test Lead #2 Test Lead #3 TLS 1 HOT GROUND OPEN GROUND TLS 2 OPEN HOT GROUND GROUND TLS 3 GROUND OPEN HOT GROUND HIPOT HOT OPEN OPEN GROUND ALL LEADS GROUND GROUND GROUND GROUND GROUND (19) FOOTSWITCH connector (20) TEST LEADS A footswitch may be connected to this socket which is in parallel to the TEST (17) button. The footswitch will operate the tester in a manner identical to the TEST button, freeing the user s hand from having to operate the switch. Test leads #1, #2, and #3 (red) and (black or ground) are provided for contact to the windings. Test leads are insulated to 45 kv. Do not touch test leads while test is in progress! User s Manual 2-5 Rev. C(11)-7/99

25 Unit Controls Tester Display A STORE RECALL PRINT CLEAR B C D (A) Menu Bar (B) Message Area E F G NOTE: The letters in parentheses ( ) below correspond to the diagram above. Storage, recall, print, and clear options for measurements obtained by the Digital Tester. The options correspond to the four function keys located directly above the display. Operations messages are also displayed in this area. Operations and print messages are displayed in this area. (C) Digital Peak Voltage Readout; Pulse Count Readout (D) Wave Pattern Display Area / Record Choice Area During testing, Surge wave patterns and DC Hipot potentials are graphically displayed here. Major and minor graticules are provided. During internal memory access, Record and Lead locations are displayed here. (E) (F) VOLTS/DIV Setting Selected Test Name (G) SECONDS/DIV or MICRO AMPS/DIV Setting Seconds/division is displayed here during Surge Testing. The micro amps/division setting is displayed here during Hipot Testing. 2-6 User s Manual Do not touch test leads while test is in progress! Rev. C(11)-7/99

26 Section 3 Storage and Print Capabilities The Digital Tester comes equipped with microcontroller based hardware that allows the user to digitize, store, recall, and print test data for up to 10 motors or windings. This applies to Surge and DC Hipot testing. The data can also be uploaded to a computer using Baker Instrument s Motor Test Acquisition (MTA 5.0 or higher) software for further analysis. There are ten Records available in memory. For each Record there are three Lead memory locations for recording three phase surge testing results. Each record can also record the results of Hipot tests. The four FUNCTION KEYS above the display correspond to the four functions displayed beneath them. The main functions are STORE, RECALL, PRINT, and CLEAR and are listed across the top of the display. Subsequent submenus also correspond to the four function keys. A description of each follows. STORE RECALL PRINT CLEAR Main Menu for data storage, recall, and print options Do not touch test leads while test is in progress! User s Manual 3-1 Rev. C(13)-7/99

27 Storage and Print Capabilities STORE STORE is used to record measurements to internal memory on the tester. NOTE: The data is permanently stored on the unit until a new record is written over it. The data cannot be cleared from the record, it can only be overwritten. Choosing STORE reveals a list of memory locations available for surge and hipot tests. Ten available Record memory locations are then listed on the display. QWK STR UP DOWN SELECT RECORD 1 RECORD 2 RECORD 3 RECORD 4 RECORD 5 RECORD 6 RECORD 7 RECORD 8 RECORD 9 RECORD 10 Listing of Record locations available for Surge and Hipot storage Choosing STORE also reveals a submenu, with choices that correspond to the four function keys above the display. STORE Record Submenu Options QWK STR UP DOWN SELECT QWK STR represents QUICK STORE. The wave pattern or hipot/pi data that is currently on the display is automatically stored in memory of the selected Record. The wave pattern will be stored in the Lead #1 location and will immediately display on the CRT. Operation will be returned to the main menu. UP moves the cursor up the Record List. DOWN moves the cursor down the Record List. Press SELECT to choose the Record that the cursor is presently on. In Surge Mode: Press SELECT to reveal the next menu for Lead selection or to cancel a selection (see next page). In Hipot Mode: Press SELECT to store Hipot and/ or PI data into the Record and return to the main menu. 3-2 User s Manual Do not touch test leads while test is in progress! Rev. C(13)-7/99

28 Storage and Print Capabilities Store Surge Data If the tester is currently in the Surge mode, the next display will allow the user to choose the Lead location in memory for Surge tests. Three Lead locations are available for each Record. CANCEL UP DOWN SELECT RECORD 1 RECORD 2 RECORD 3 RECORD 4 RECORD 5 RECORD 6 RECORD 7 LEAD 1 LEAD 2 LEAD 3 Listing of Lead locations available for Surge storage Store Hipot and PI Data If the tester is currently in the Hipot mode, the next display will allow the user to choose whether to store Hipot of Polarization Index data into memory. CANCEL UP DOWN SELECT RECORD 1 RECORD 2 RECORD 3 RECORD 4 RECORD 5 RECORD 6 HIPOT PI Listing of Lead locations available for Hipot and PI storage STORE Lead Submenu Options CANCEL UP DOWN SELECT Press CANCEL to return to the main menu without storing any data. Note: This option does not clear data out of memory on the tester. Data may only be overwritten. UP moves the cursor up the Lead List. DOWN moves the cursor down the Lead List. Press SELECT to choose the Lead of Hipot data type that the cursor is on. Data will be loaded into memory. The user will be returned to the main menu. Do not touch test leads while test is in progress! User s Manual 3-3 Rev. C(13)-7/99

29 Storage and Print Capabilities RECALL RECALL is used to retrieve measurements from internal memory to the display. Choosing RECALL reveals a list of memory locations available for surge and hipot tests. Ten available Record memory locations are then listed on the display. SUMMARY UP DOWN SELECT RECORD 1 RECORD 2 RECORD 3 RECORD 4 RECORD 5 RECORD 6 RECORD 7 RECORD 8 RECORD 9 RECORD 10 Listing of Record locations available for Surge and Hipot recall Choosing RECALL also reveals a submenu, with choices that correspond to the four function keys above the display. RECALL Record Submenu Options SUMMARY UP DOWN SELECT Press SUMMARY to display the Surge data in all three Leads, the Hipot, and the PI data stored in the Record the cursor is presently on. All three wave patterns, Hipot, and PI results will be displayed simultaneously and operation will be returned to the main menu. UP moves the cursor up the Record List. DOWN moves the cursor down the Record List. Press SELECT to choose the Record that the cursor is presently on. In Surge Mode: Press SELECT to reveal the next menu for Lead selection or to cancel a selection (see next page). In Hipot Mode: Press SELECT to recall Hipot and/ or PI data from the Record and return to the main menu. 3-4 User s Manual Do not touch test leads while test is in progress! Rev. C(13)-7/99

30 Storage and Print Capabilities Recall Surge Data If the tester is currently in Surge mode, the next display allows the user to choose the Lead location from which to recall a wave pattern. Three Lead locations are available for each Record. CANCEL UP DOWN SELECT RECORD 1 RECORD 2 RECORD 3 RECORD 4 RECORD 5 RECORD 6 RECORD 7 RECORD 8 RECORD 9 RECORD 10 LEAD 1 LEAD 2 LEAD 3 Listing of Lead locations available for Surge recall RECALL Lead Submenu Options CANCEL UP DOWN SELECT Press CANCEL to return to the main menu without recalling any data. Note: This option does not clear data out of memory on the tester. UP moves the cursor up the Lead List. DOWN moves the cursor down the Lead List. Press SELECT to choose the Lead that the cursor is presently on. Surge data is recalled from memory to the display and the user is returned to the main menu. Recall Surge Data NOTE: RECALL displays only one wave pattern from memory and clears any wave pattern that has been previously recalled to the screen. See Three Phase Motor Surge Test and Set-Up, Step 9 on page 6-8 for procedures to compare two surge wave patterns simultaneously. If the tester is currently in Hipot mode, the tester will display the recorded Hipot and Poloarization Index data for the selected Record. Do not touch test leads while test is in progress! User s Manual 3-5 Rev. C(13)-7/99

31 Storage and Print Capabilities PRINT PRINT will output the present display to an Epson FX compatible dot matrix printer connected to the tester. (Refer to the manual that came with your printer for the DIP switch settings that make the printer Epson FX compatible.) Error messages associated with printing, if there are any, will appear on the screen. Sample printout of the Digital Tester CLEAR CLEAR will remove or blank-out the wave pattern and message area of the display. It has no affect on memory locations or the data stored there. 3-6 User s Manual Do not touch test leads while test is in progress! Rev. C(13)-7/99

32 Section 4 Test Procedures and Voltages Throughout this manual, Baker Instrument Company will recommend various procedures that should be followed for the most efficient and safe use of your tester. These procedures have been developed through constant feedback from you, the user. Baker Instrument Company recommends that you perform the DC Hipot test first, in order to determine if a winding s ground wall insulation has failed. Ifthis occurs, it is not necessary to proceed with any further testing the winding is bad. If the test piece passes the DC Hipot test, it is then appropriate to proceed with the Surge test. General User Cautions and Notes Irregularities, particularly vertical spikes, may be seen in the first cycle of the surge wave pattern. These occur most frequently on large, high voltage motors. Do not interpret these as faults in the windings. Any winding fault will be seen throughout the entire wave pattern. DO NOT change the TEST Lead SELECT (TLS) switch setting while a test is being made. Doing so will cause arcing and damage the switch contacts, resulting in improper operation and accelerated aging of the instruments components. DO NOT switch the FUNCTION CONTROL between Surge and Hipot settings during testing. It is only acceptable to alter Hipot current settings while in the Hipot mode. When increasing the applied voltage during a test, use a higher VOLTS/DIV setting so the entire wave pattern or trace stays visible on the screen. It is acceptable to change this setting while testing. The VOLTS/DIV control has no effect on and does not limit the output voltage of the tester. It only controls the display scale. The Digital surge tester is equipped with a Zero Start Interlock assembly that requires the return of the OUTPUT control to MIN (zero) before the start of each test. Advances in electronics and Baker Instrument Company s design have made fault detection sensitivity greater than on older models. It is not uncommon to see separation of compared wave patterns with newer models when the same comparison may show no separation on an older surge tester. Baker Instrument Company testers often show separation caused by concentric Do not touch test leads while test is in progress! User s Manual 4-1 Rev. C-7/99

33 Test Procedures and Voltages (basket) winds and capacitance or magnetic imbalances. Care should be taken when interpreting SLIGHT SEPARATION seen when Surge Comparison testing. ALWAYS unclip the test leads. Do not jerk or pull them from the motor leads! NEVER connect test leads from two or more testers on the same load. This includes connection of host and power pack unit leads to the same load. This warning also includes lead connections, even for grounding purposes. Please do not hesitate to contact Baker Instrument Company for technical applications assistance at (970) or toll free at Or FAX your questions, information, printouts, diagrams, or photographs of your test to (970) Initial Tester Power-Up and Check-Out NOTE: Each Baker Instrument Company Tester incorporates a supply ground detection circuit. This circuit assures a positive grounding of the tester. If the instrument is not properly grounded, the OPEN GRD indicator will light and testing cannot proceed. Check the supply to the tester (broken ground, bad extension cord, excessive ground to neutral voltage) and assure that a low impedance ground is provided to the unit. 1. Check that the ON/OFF switch is in the OFF position. 2. Connect the tester power cord to a VAC outlet (or VAC outlet if appropriate). The tester will work on either 60 Hz or 50 Hz. 3. Set the OUTPUT control to MIN (fully counterclockwise). 4. Turn the tester ON/OFF switch to ON. Allow a brief period for CRT warm-up. The following messages should appear on the screen. Testing Internal Mem ory... OK Testing CRT Mem ory... OK Testing A-to-D Mem ory... OK Testing Eeprom Mem ory... OK 4-2 User s Manual Do not touch test leads while test is in progress! Rev. C-7/99

34 Test Procedures and Voltages A self-test is performed on the Digital tester for all internal memory modules when the tester is powered up. Any failures will be noted on the CRT display. If the CRT does not display anything, turn the unit OFF immediately and recheck Step 2. Also, check that the INTENSITY is not turned fully counterclockwise. Turn the tester ON to obtain a display on the CRT. If no display is noticed, turn the unit off and call Baker Instrument Company s Service Department. Refer to Warranty Notes on page iii and Appendix B: Troubleshooting for calling information. 5. The unit is now ready for testing. Recommended Voltages A recommended value for DC High Potential and Surge voltage to test a motor, generator, or transformer in service is twice the line voltage plus 1000 volts. This test voltage value is consistent with NEMA MG-1, ANSI/IEEE (test voltages greater than 5000 V) and IEEE (test voltages less than 5000 V). Examples for 460 and 4160 volt motors are as follows: 2 x 460 V= 920 V V = 1920 V 2 x 4160 V = 8320 V V = 9320 V For new windings or rewound motors, this potential is sometimes increased by a factor of 1.2 or as much as 1.7. This provides for a higher level of quality control on the work performed. For the above 460 V motor, the test voltage may be: 1920 V x 1.2 = 2304 V or as high as 1920 V x 1.7 = 3264 V NOTE: Although the CRT display is accurately calibrated, it is not possible to discern small or minor voltage increments. It is suggested that the formula answers be rounded off, or more specifically, rounded to the nearest minor graticule division discernible. Follow all safety procedures detailed in IEEE Std , Recommended Practice for Insulation Testing of Large AC Rotating Machinery with High Direct Voltage (Reaff 1991) and other standards. Some of the applicable standards are listed here: IEEE IEEE IEEE Recommended Practice for Testing Insulation Resistance of Rotating Machinery (Reaff 1991) Guide for Insulation Maintenance of Large AC Rotating Machinery (10,000 kva and Larger) (Reaff 1991) Test Procedures for Polyphase Induction Motors and Generators (ISBN ) Do not touch test leads while test is in progress! User s Manual 4-3 Rev. C-7/99

35 Test Procedures and Voltages IEEE Guide on Test Procedures for DC Machines IEEE Test Procedures for Synchronous Machines (Reaff 1991) IEEE IEEE IEEE IEEE Evaluation of Sealed Insulation Systems for AC Electric Machinery Employing Form-Wound Stator Coils Guide for Insulation Maintenance for Rotating Electrical Machinery (5 hp to less than hp) (ISBN ) Guide for Functional Evaluation of Insulation Systems for Large High-Voltage Machines (Reaff 1991) Guide for Testing Turn-To-Turn Insulation on Form-Wound StatorCoils for Alternating-Current Rotating Electric Machines (ISBN ) Reprints of these articles may be obtained by contacting: IEEE Customer Service 445 Hoes Lane P.O. Box 1331 Piscataway, NJ Phone: IEEE (4333) FAX: User s Manual Do not touch test leads while test is in progress! Rev. C-7/99

36 Section 5 DC Hipot Test Understanding Hipot Testing As discussed in Principles of DC High-Potential (Hipot) Testing on page 1-1, the hipot test is considered the mainstay of motor testing. Hipots can be performed in one oftwo ways, AC or DC. Although the Surge test will test for grounds, it does not uniformly test all the ground wall insulation as thoroughly as the Hipot test. Nor does the Surge test give a quantitative value of the leakage current to ground. The Hipot test is made specifically for insulation resistance measurement. The Hipot brings the entire motor winding up to the same potential. Since all the windings are at the same potential, there is no turn to turn, or phase to phase insulation stress. There is uniform voltage stress applied between the winding insulation and the ground wall, throughout the entire winding. The theory behind the test is based on simple leakage current. Given any good insulation, the current leakage through the insulation should be very low and therefore the insulation resistance very high, and visa versa. The formula associated with this test is R = E / I. Written out, the formula states that resistance is equal to voltage divided by current. Or put another way, resistance is inversely proportional to current for a given voltage. The Hipot tester provides a voltage, in most cases, variable to some limit. The resistance is that of the ground wall insulation to ground or the motor frame. Using the formula, the higher the resistance for a given voltage, the lower the leakage current, and vice versa. Baker Instrument Company testers provide the DC Hipot test as a separate and added function to the Surge testing unit. The digital tester provides a variable voltage source to apply to motor windings, a state of the art CRT display for both voltage and current readings, digital display of the calculated resistance of the test motor, and storage capabilities for up to 10 measurements in internal memory. During a typical DC Hipot test, all motor output leads are tied together and connected to test lead #1. The tester ground lead is connected to the motor frame. The output voltage is raised to some predetermined test voltage and a current reading is measured. The Digital Tester automatically calculates the resulting resistance to the leakage current. The lower the leakage current reading for the given voltage, the better the ground wall insulation. Do not touch test leads while test is in progress! User s Manual 5-1 Rev. C(13)-7/99

37 DC Hipot Test The Hipot Test Display A B STORE RECALL PRINT TIME=0 Time: Min: 533MΩ PI: 1.50 C D E 1600 V 800 MΩ 2 u-amps F 1000 V/div HIPOT 1 u-amps/div The letters below in parentheses correspond to the diagram above. (A) (B) (C) (D) (E) (F) Main Menu for Function buttons and Message area Time Duration of Hipot test; Resistance Measurement after one minute; Polarization Index* result Voltage Bar Current Bar Digital Peak Voltage; Resistance Measurement; Current Measurement VOLTS/DIV Setting; Current Test Name; µ-amps/div Setting * The Polarization Index (PI) test begins when the TEST button is pressed for a Hipot test. It is defined as the measured resistance at ten minutes divided by the measured resistance at one minute. Refer to Section 8: Additional Tests for more information regarding the Polarization Index test. 5-2 User s Manual Do not touch test leads while test is in progress! Rev. C(13)-7/99

38 DC Hipot Test DC Hipot Test and Set-Up NOTE: Check the circuits to guarantee that capacitors or other devices are not connected. Not only could this be hazardous to the person performing the test, but they will also produce inaccurate measurements. 1. Turn the FUNCTION switch to one of the DC HIPOT µ-amps/div settings. The lower, center portion of the screen will display the test name, HIPOT, and will show that the divisions on the screen are now micro-amps/division. NOTE: Test standards recommend starting at the 100 micro-amp/division setting. In the event of a dead short, the fault will still be readily detectable. The lowest setting gives the operator the greatest sense of understanding and control of what is occurring as the winding is being charged up during the test. However, the desired test voltage can be reached faster by initially using the highest setting. This setting decreases sensitivity and prevents overcurrent tripping due to charging currents. 2. Rotate the TEST Lead SELECT (TLS) to the HIPOT setting. This selects the red test lead #1 as HOT. The black lead is the GROUND. Leads #2 and #3 are open. 3. Ensure the OUTPUT control is set at MIN, fully counterclockwise. 4. Check the circuits to ensure that capacitors or other devices are not connected. Not only could this be hazardous to the person performing the test, but it will also provide inaccurate results. 5. On multi-lead equipment, all equipment leads should be connected to lead #1 of the tester. Use jumpers to facilitate this procedure. Winding leads that are not connected to the tester s lead #1 may be at the same or higher voltage potential as the test voltage and potentially hazardous. 6. Connect the black GROUND lead to a clean ground on the frame or core of the equipment under test. NOTE: It is NOT recommended to use the motor junction box for grounding. Do not touch test leads while test is in progress! User s Manual 5-3 Rev. C(13)-7/99

39 DC Hipot Test test leads #2 & 3 ground lead ground lead test lead #1 test lead #1 Examples of how to connect the test leads to the motor for Hipot testing. 7. To test, depress and hold the TEST button and slowly raise the voltage with the OUTPUT control. NOTE: The rate at which the OUTPUT control is increased affects the amount of current necessary to charge the winding. Slowly raising the OUTPUT control (voltage) will keep charging current at low levels. Monitor the current indication on the right half of the CRT display to observe the charging current levels. CAUTION! THIS TEST SHOULD BE STOPPED ANY TIME A FAST, SHARP RISE IN THE CURRENT IS SEEN. WARNING! USE EXTREME CAUTION. COMPLETELY DISCHARGE THE EQUIPMENT UNDER TEST BY MOVING THE TLS POSITION TO LEADS GROUND FOR A TIME EQUAL TO THE DURATION OF THE TEST JUST COMPLETED. As the voltage is applied to the motor, two horizontal lines appear on the display. The applied voltage is seen on the left half of the display as a steadily rising horizontal line. The current, also a horizontal line, will rise and fall on the right half of the display, showing the current necessary to charge the windings. Once the winding is charged the current falls. The steady state current is the leakage current level. 5-4 User s Manual Do not touch test leads while test is in progress! Rev. C(13)-7/99

40 DC Hipot Test Digital readings also appear on the display just below the voltage and current traces. From left to right they are test voltage, calculated resistance in megaohms, and leakage current in micro-amps. NOTE: Leakage current readings will not be accurate until the proper micro-amps/division has been selected. Adjust the micro-amps/ division switch until the error message, Change to lower microamps/ divsion setting, no longer appears on the screen before reading the leakage current. Hipot Test in Progress... TIME=0 Time: Min: 2053MΩ PI: 1.50 Hipot Test in Progress... TIME=0 Time: Min: 162MΩ PI: V 2900 MΩ 2 u-amps 1000 V/div HIPOT 1 u-amps/div Good insulation with high voltage and low leakage current V 28 MΩ 7 u-amps 1000 V/div HIPOT 1 u-amps/div Poor insulation with low voltage and high leakage current. 8. Once the test voltage has been reached, turn the micro-amps/division switch to the lowest setting that will still display a current bar on the screen. 9. When the desired test voltage has been achieved, press the TIME=0 FUNCTION button (the right-most button above the CRT display). The elapsed time displayed in the upper left corner of the screen will reset to zero. NOTE: Use TIME=0 function to be sure the full DC voltage potential is applied for the required test time. In this way, the time required for voltage rampup will be discounted for both Hipot and Polarization Index tests. 10. Maintain the test potential for one (1) minute. If instability or a sharp rise in the current (right half of display) is noted, discontinue the test immediately. 11. When the test is complete, release the TEST button. The digital readings of the test will not change. The horizontal bars that represent voltage and current will continue to display their readings after the TEST button is released. The voltage bar will gradually return to the baseline as the winding capacitance is discharged through the internal resistance of the tester. Do not touch test leads while test is in progress! User s Manual 5-5 Rev. C(13)-7/99

41 DC Hipot Test Store the Results in Memory 1. Press the function key corresponding to STORE. A list of available Records appears. The menu bar at the top of the screen also changes. 2. Press the function keys corresponding to the UP and/or DOWN to bring the cursor to the desired Record. Press SELECT. 3. Be sure HIPOT is highlighted in the second column. (Press the function keys corresponding to the UP and/or DOWN as necessary.) The Hipot value will be stored to the record that is selected. The main menu will reappear and the next motor may be tested. NOTE: Upon completion of the hipot test, allow a sufficient time for the equipment under test to discharge completely. Recommended practice is to ground the leads of the equipment under test for a time equal to the time the test potential was applied. Use of the TLS LEADS GROUND position is recommended. DC Hipot Over-Current Trip The Digital tester is equipped with an Auto-Ranging Hipot Over-Current safety trip. If the Hipot current levels go too high, this over-current trip will stop the test. The red HIPOT TRIP lamp on the front panel will light. The over-current trip point is ten (10) times the µ-amps/div setting selected on the FUNCTION knob. Releasing the TEST button resets the trip in which case the red HIPOT TRIP lamp will go off, and the unit is ready to begin testing again. Windings that are grounded will cause the current trace to quickly go off screen and the DC Hipot Over-Current Trip to activate. DC Hipot Application Tips A poor ground connection may cause a device to show no leakage current. It appears the device has infinite resistance to ground. This can be misleading and cause a bad motor to test as good. NOTE: Before beginning the DC Hipot test, the Hipot Over-Current safety trip may be used to verify that a good ground has been made with the black GROUND lead. After making the connection to the frame (ground) with the GROUND lead, connect RED lead #1 to another point on the frame. Keep the OUTPUT control at MIN and press the TEST button. Agood ground connection will activate the overcurrent trip at the slightest increase of output (trip sensitivity is affected by current setting). If the trip does not operate, reconnect the ground and repeat this test. Ensure the continuity of the GROUND lead. Often the paint on the device is preventing a good ground and may need to be scraped off. 5-6 User s Manual Do not touch test leads while test is in progress! Rev. C(13)-7/99

42 DC Hipot Test The DC Hipot test component of the Digital tester can test the insulation between any two conductors. For example, it may be used to test the insulation between feeder cables which are disconnected from a motor. Place the HOT lead on one cable and the GROUND lead on the others. Follow the same procedures outlined for DC Hipot testing. Change these connections to test all cables. Resistance Temperature Compensation When DC Hipot testing, temperature WILL have an influence which distorts your results. It is also important to ensure that the test piece s insulation is dry and dirtfree. The rule of thumb for determining the effect of temperature on resistance measurements is that resistance halves for each 10 degrees Celsius rise in winding temperature. Usually, the baseline temperature is 40 degrees Celsius for windings. This rating is usually found on the motor s data plate. The following two examples illustrates this relationship: EXAMPLE 1: If a resistance measurement of 100 mega-ohms is taken at 30 degrees Celsius, the resistance should be 50 meg-ohms at 40 degrees Celsius (an increase of 10 degrees Celsius). EXAMPLE 2: If a resistance measurement of 200 mega-ohms is taken at 50 degrees Celsius, the resistance should be 400 meg-ohms at 40 degrees Celsius (a decrease of 10 degrees Celsius). Do not touch test leads while test is in progress! User s Manual 5-7 Rev. C(13)-7/99

43 DC Hipot Test 5-8 User s Manual Do not touch test leads while test is in progress! Rev. C(13)-7/99

44 Section 6 Surge Testing Discussed in The Principles of Surge Testing on page 1-3, the Surge and Surge Comparisons test is the most thorough method of determining the quality of the inter-turn insulation of windings and coils. Unlike other tests, the Surge test can detect the early stages of turn-to-turn insulation failure. Surge Test The most basic type of Surge test is used for testing the turn-to-turn insulation of coils and single windings. Form coils, start and run windings, and multi-tapped windings are a few examples. Surge testing can also be used for standards testing. Here, a winding that is known to be good is selected as the standard. It is then used to test against the test windings. For the surge test, the hot output lead is attached to one lead of the coil or winding and a ground or return lead is attached to the opposite lead. The test is complete when the coil is tested in both directions by reversing the leads. Complete instructions for Surge testing can be found, starting with Single Coil Surge Test and Set-Up on page 6-3. Surge Comparison Test Surge comparison tests are used for simultaneous comparisons of coils or windings, usually for three-phase motors. Ideally, all phases of a three-phase motor are identical. That is they have the same number of turns, are wound in the same direction, and have the proper connections. Therefore, a comparison of surge test wave patterns should be identical. Each phase of a three phase motor is compared to the other. If the phases are identical, the wave patterns will superimpose. If there is a fault in a phase, its wave pattern will differ from those of the others. Specifically, the inductance of a winding may decrease due to turn-to-turn faults, phase-to-phase faults, misconnections, open connections, etc. Accordingly, the surge wave pattern will be lower in frequency and amplitude than an identical winding of higher inductance which is free of faults. During surge comparison testing, each winding is surge tested and the resulting wave patterns are displayed simultaneously in pairs. If all three pairs superimpose exactly, the motor is good. If not, there will be at least two pairs that show differing wave patterns. The fault is located within the phase the is common to the two surge pairs that differ. Do not touch test leads while test is in progress! User s Manual 6-1 Rev. C(11)-7/99

45 Surge Testing Complete instructions for Surge Comparison testing can be found, starting with Three Phase Motor Surge Test and Set-Up on page 6-6. CAUTION Before proceeding with any test, refer to General User Cautions and Notes on page 4-1 of this manual. The Surge Test Display A STORE RECALL PRINT CLEAR B C Peak: 9000 V Pulse: 45 D E 3000 V/div SURGE 2 us/div The letters below in parentheses correspond to the diagram above. (A) (B) (C) (D) (E) Main Menu Digital Peak Voltage Readout Number of Surge Pulses applied to the test winding Example of a Surge Wave Pattern VOLTS/DIV Setting; Current Test Name; SECONDS/DIV Setting 6-2 User s Manual Do not touch test leads while test is in progress! Rev. C(11)-7/99

46 Surge Testing Single Coil Surge Test and Set-Up NOTE: Check to ensure there is nothing connected to the coil or winding being tested. This is extremely important when testing installed coils or windings. Test inaccuracies will result and can be hazardous to personnel performing tests. 1. With the TEST Lead SELECT (TLS) switch in the LEADS GROUND position, make the following connections. Refer to the table, Test Lead Connections on page 2-5 for lead information. a. Connect the #1 lead on one side of the coil or winding. b. Connect test lead #2 to the other side of the coil or winding. c. Connect the black Ground lead and test lead #3 to the frame or housing of the coil or winding. test lead #1 test lead #2 Example of how to connect test leads for Single Coil Surge Testing 2. Turn the FUNCTION switch to the SURGE position. The surge display should be blank with a dashed horizontal line centered in it. This line is the reference ZERO or BASE LINE. 3. Select TLS position #1. This lead will be HOT. 4. Set the VOLTS/DIV switch at the lowest setting that will allow the maximum pattern to be viewed entirely on the CRT. Do not touch test leads while test is in progress! User s Manual 6-3 Rev. C(11)-7/99

47 Surge Testing Example: For a test voltage of 2000 V, a VOLTS/DIV setting of 500 will give a wave pattern with 4 divisions of amplitude that doesn t go off screen. For a test voltage of 4000 V, a setting of 500 VOLTS/DIV would result in a wave pattern with 8 divisions amplitude which would go off the screen. 5. Testing may now begin in the following manner: a. Set the OUTPUT CONTROL to MIN by rotating it fully CCW. b. Depress and hold the TEST button (or FOOTSWITCH). The LEADS ENERGIZED light will come on, indicating that the test lead is hot. c. SLOWLY raise the OUTPUT control, applying voltage to the test windings. Carefully monitor the trace on the display and adjust the VOLTS/DIV, and SECONDS/DIV controls to get the best waveform possible. d. Adjust the OUTPUT and VOLTS/DIV controls to the desired voltage level while maintaining a fully visible wave pattern on the CRT display. The voltage is measured from the zero line to the first positive peak (at the far left) of the trace multiplied by the display VOLTS/DIV setting. The peak voltage is numerically displayed in the upper right portion of the Surge test display. e. When the test for the lead is complete, the TEST may be released. Return the OUTPUT CONTROL to MIN. The LEADS ENERGIZED light will turn off. 6. If the surge wave pattern appears steady and stable, the winding insulation is sufficient to withstand the applied voltage and the test is successful. NOTE: If the wave pattern begins to flicker or rapidly shift left and right and/or up and down as the OUTPUT is increased, there is weakness in the winding insulation and intermittent arcing between the windings or phases. The winding or phase contains a fault when the wave pattern shifts to the left and the amplitude drops. The more severe the shift and amplitude drop, the more severe the fault. Faults are often accompanied by an audible arcing sound. When an obvious fault is present, the motor is bad. Perform Step 7 below and end the test by disconnecting the motor from the tester. 7. Store the results in the tester s memory. a. For testing a single coil or for standards testing, store the pattern using QUICK STORE. i. Press the function key corresponding to STORE. A list of available Records and Leads appear. The menu bar at the top of the screen also changes. ii. Press the key corresponding to QWK STR. The wave pattern is now stored in Record #1, Lead #1 and is immediately recalled onthe screen. 6-4 User s Manual Do not touch test leads while test is in progress! Rev. C(11)-7/99

48 Surge Testing b. When surge testing several motors or for tests that are to be downloaded to a personal computer for further analysis, store the pattern conventionally. i. Press the function key corresponding to STORE. A list of available Records appears. The menu bar at the top of the screen also changes. ii. Press the keys corresponding to the UP and/or DOWN to bring the cursor to the desired Record. Press SELECT. iii. Repeat Step ii above for the desired Lead. NOTE: The flicker in wave patterns that is observed when there is arcing between the windings or phases cannot be stored in the Digital tester. As soon as the TEST button is released, the wave pattern freezes. This is the only wave pattern that can be stored. It is desirable to store the wave pattern produced by this arcing for reference. The operator must attempt to release the TEST (thus freezing the wave pattern for storage) at the moment when the wave pattern appears the most affected by the fault (reduced amplitude and higher frequency). 8. Leave the TLS position at #1. 9. Switch the test leads: connect the #2 lead where the #1 lead s position and connect the #1 where #2 lead was. a. If the first wave pattern was stored using QUICK STORE, simply compare the two wave patterns on the screen and make an analysis of the condition of the coil. See Determination of a Fault on page 6-14 and/or Section 7: Surge Test Applications for instructions on how to interpret surge wave patterns. NOTE: Some adjustment of the Horizontal and Vertical Position of the wave pattern may be necessary to superimpose the wave patterns. b. If the first wave pattern was stored conventionally and subsequent wave patterns are to be stored for further analysis repeat Step b under Step 7 above. NOTE: It is convenient to store the results of a single motor into a single Record. Store the two wave patterns for the coil into two Lead locations for the desired Record. The results of up to ten motors can be stored on the Digital tester. In summary, for each direction the coil is tested, you will check the display for the wave pattern produced in each test. If you see two good stable patterns, the winding is good. If you see anything other than good patterns there is a possible fault. Refer to Determination of a Fault on page 6-14 for explanations of wave patterns indicating good or faulty windings. Refer to Section 7: Surge Test Applications for descriptions of wave patterns for a variety of devices. Keep in mind, fault determination is often a result of experience. Do not touch test leads while test is in progress! User s Manual 6-5 Rev. C(11)-7/99

49 Surge Testing Example: Comparison to a Master Coil Occasionally, a manufacturer may want to test against a standard. The selected standard coil is surge tested. The results are stored in memory and recalled to the screen. (QUICK STORE is useful for this situation.) All unknown coils would be tested and compared to the stored and displayed wave pattern of the standard coil. Standards testing demonstrates the coil s ability to withstand minimum test voltages and the signature waveform can be compared to the standard s single waveform. Three Phase Motor Surge Test and Set-Up NOTE: Check to ensure there is nothing connected to the coil or winding being tested. This is extremely important when testing installed coils or windings. Test inaccuracies will result and can be hazardous to personnel performing tests. 1. With the TLS switch in the LEADS GROUND position, make the appropriate connections: a. Connect all three red test leads to the motor input leads. Any order is fine but Baker Instrument Company recommends connecting test lead #1 to motor output lead #1, #2 to #2, and #3 to #3 if the data will be stored and maintained for reference. b. Connect the black Ground lead to the frame or housing of the motor. ground lead ground lead test leads #1, 2, 3 test leads #1, 2, 3 Examples of how to connect test leads for Three Phase Motor Surge Testing 6-6 User s Manual Do not touch test leads while test is in progress! Rev. C(11)-7/99

50 Surge Testing 2. Turn the FUNCTION switch to the SURGE position. The surge display should be blank with a dashed horizontal line centered in it. This line is the reference ZERO or BASE LINE. 3. Set the VOLTS/DIV switch at the lowest setting that will allow the maximum pattern to be viewed entirely on the CRT. Example: For a test voltage of 2000 V, a VOLTS/DIV setting of 500 will give a wave pattern with 4 divisions of amplitude that doesn t go off screen. For a test voltage of 4000 V, a setting of 500 VOLTS/DIV would result in a wave pattern with 8 divisions amplitude which would go off the screen. 4. Select TLS position #1. This lead will be HOT. Refer to Test Lead Connections on page 2-5 for lead information. 5. Testing may now begin in the following manner: a. Set the OUTPUT CONTROL to MIN by rotating it fully CCW. b. Depress and hold the TEST button (or FOOTSWITCH). The LEADS ENERGIZED light will come on indicating that the TLS lead is hot. c. SLOWLY raise the OUTPUT control, applying voltage to the windings under test. Carefully monitor the trace on the display and adjust the VOLTS/DIV, and SECONDS/DIV controls to get the best waveform possible. d. Adjust the OUTPUT and VOLTS/DIV controls to the desired voltage level while maintaining a fully visible wave pattern on the CRT display. The voltage is measured from the zero line to the first positive peak (at the far left) of the trace multiplied by the display VOLTS/DIV setting. The peak voltage is numerically displayed in the upper right portion of the Surge test display. e. When the test for the lead is complete, the TEST may be released. Return the OUTPUT CONTROL to MIN. The LEADS ENERGIZED light will turn off. 6. If the surge wave pattern appears steady and stable, the winding insulation is sufficient to withstand the applied voltage and the test is successful. NOTE: If the wave pattern begins to flicker or rapidly shift left and right and/or up and down as the OUTPUT is increased, there is weakness in the winding insulation and intermittent arcing between the windings or phases. The winding or phase contains a fault when the wave pattern shifts to the left and the amplitude drops. The more severe the shift and amplitude drop, the more severe the fault. Faults are often accompanied by an audible arcing sound. When an obvious fault is present, the motor is bad. Perform Step 7 below and end the test by disconnecting the motor from the tester. Do not touch test leads while test is in progress! User s Manual 6-7 Rev. C(11)-7/99

51 Surge Testing 7. Store the results in the tester s memory. a. Press the function key corresponding to STORE. A list of available Records appears. The menu bar at the top of the screen also changes. b. Press keys corresponding to the UP and/or DOWN to bring the cursor to the desired Record. Press SELECT. c. Repeat Step ii above for the desired Lead. NOTE: The flicker in wave patterns observed when there is arcing between the windings or phases cannot be stored in the Digital tester. As soon as the TEST button is released, the wave pattern freezes. This is the only wave pattern that can be stored. It is desirable to store the wave pattern produced by this arcing for reference. The operator must attempt to release the TEST (thus freezing the wave pattern for storage) at the moment when the wave pattern appears the most affected by the fault (reduced amplitude and greater frequency). 8. Repeat Step 5 thru Step 7 for each position of the TLS (positions #2 and then position #3), bringing the peak voltage to the same value used in the first test. Refer to Test Lead Connections on page 2-5 for lead information. NOTE: It is convenient to store the results of a single motor into a single Record. Store the three individual wave patterns for the phases into the three Leads associated with that single Record. The results of up to ten motors can be stored on the Digital tester. 9. Perform a Surge Test Comparison to determine if there is an individual coil or phase with winding faults. The basic method here is to compare all the wave patterns for each winding or coil in pairs. For identical windings, all three wave patterns should be identical. If one or two windings are different in any way, the wave patterns will show differences when compared. Baker Instrument Company recommends detecting these differences by comparing their patterns in pairs in the following manner. a. Recall to the screen the wave pattern for test lead #1. i. Press the function key corresponding to RECALL. A list of available Records appears. The menu bar at the top of the screen also changes. ii. Press keys corresponding to the UP and/or DOWN to bring the cursor to the desired Record. Press SELECT. iii. Repeat Step ii above for Lead #1. The surge wave pattern for this lead then appears on the screen. 6-8 User s Manual Do not touch test leads while test is in progress! Rev. C(11)-7/99

52 Surge Testing iv. Repeat a surge test using test lead #2. (In other words, repeat Step 5 for test lead #2.) The wave pattern should appear together with the recalled wave pattern. Be sure to match the output voltage of the recalled wave. v. Carefully attempt to superimpose the two wave patterns. Adjustments of the Horizontal and Vertical positions may be required to properly overlay the two wave patterns. vi. Observe the two wave patterns for any separation. If they are identical and superimpose on each other they will appear to be one wave. If there is a slight shift to the left of one wave, make a note of the lead that is showing the shift. b. Repeat Step a under Step 9 for test leads #1 and #3 where #1 is recalled and #3 is retested. c. If all the wave patterns are identical, the motor windings are good. If one of the wave patterns shows separation, that lead is connected to the faulty winding. NOTE: A good way to check the wave patterns after the test is complete is to display all three wave patterns at once. To do so, press the function key that corresponds to RECALL. Press the keys that correspond to UP and/ or DOWN to bring the cursor to the desired Record and then press the key that corresponds to SUMMARY. The data that was stored for all three Lead locations for that Record will appear on the display along with any recorded Hipot data. In general, for each phase or coil of the motor that is tested, you will check the display for a wave pattern and compare it to another wave pattern for that motor. If you see three good, stable patterns that are identical to each other, the motor is good. If you see anything other than good patterns or separation in the patterns when compared there is a possible fault. Refer to Determination of a Fault on page 6-14 and Section 7: Surge Test Applications for more information. Keep in mind, fault determination is often a result ofexperience. Do not touch test leads while test is in progress! User s Manual 6-9 Rev. C(11)-7/99

53 Surge Testing Surge Voltage Measurement During the surge test, adjust the OUTPUT and VOLTS/DIV controls to the desired voltage level while maintaining a fully visible wave pattern on the display. The voltage is measured from the zero line to the first positive peak (at the far left) of the trace. The peak-to-peak measurement is NOT significant. Measured output voltage is the number of divisions corresponding to the first peak of the wave pattern multiplied by the VOLTS/DIV setting. The following figures illustrate various voltage readings for a single setting of 500 VOLTS/DIV. STORE RECALL PRINT CLEAR STORE RECALL PRINT CLEAR Peak: 500 V Pulse: 35 Peak: 1000 V Pulse: V/div SURGE 2 us/div 500 V/div SURGE 2 us/div 1 division x 500 V/Div = 500 Volts 2 divisions x 500 V/Div = 1000 Volts STORE RECALL PRINT CLEAR STORE RECALL PRINT CLEAR Peak: 1500 V Pulse: 35 Peak: 2000 V Pulse: V/div SURGE 2 us/div 500 V/div SURGE 2 us/div 3 divisions x 500 V/Div = 1500 Volts 4 divisions x 500 V/Div = 2000 Volts 6-10 User s Manual Do not touch test leads while test is in progress! Rev. C(11)-7/99

54 Surge Testing Factors Affecting the Surge Tester s Output The tester s maximum size AC motors recommended for test are given on the tester s specifications sheet (see Technical Specifications on page iv). This recommendation is based on the ability to generate the necessary recommended test voltage of 2E volts, where E is the motor s rated operating voltage. Several factors may individually, or in combination, reduce the ability of a surge tester to generate the recommended test voltage. It should be noted that in some cases, with adapted test procedures, motors larger than the recommended maximum size to test have been successfully tested to the recommended test voltage levels. In many cases, a larger, higher output voltage surge tester that is overrated for particular motor sizes may be needed if factors exist which will load the tester s output. The following table of information shows various factors which will reduce the output voltage of a Baker Instrument Company Surge Tester below its maximum rating. The table is based on general information and does not comprehensively cover every motor and/or cable design or configuration that exists. CAUTION OUTPUT SHOULD NOT BE INCREASED ANY FURTHER IF ARCING OR AN UNSTABLE CONDITION IS NOTED! FACTOR Motor Larger Than Recommended Max Size to Test Motor RPM is Slow Motor has high # poles EFFECT Capacitance and inductance of motor windings load the tester output down. Voltage output is reduced below maximum. Can damage tester if test is applied for an extended period of time. It should be noted that the test is considered successful if the test voltage 2E V is achieved (though that voltage may be below the maximum rated output of the tester). For each reduction of the motor s RPM (i.e > 1800) the effective horsepower of the motor that the Surge Tester senses is doubled. Example: A 500 hp/3600 RPM motor = 500 hp. A 500 hp/1800 RPM motor = 1000 hp. A 500 hp/900 RPM motor =2000 hp, etc. Same condition as above. Reference above comments on motor RPM. Do not touch test leads while test is in progress! User s Manual 6-11 Rev. C(11)-7/99

55 Surge Testing FACTOR Feeder Cable Length Feeder Cable Shielded High Horsepower Motors at Low Operating Voltage Motor Assembled with Rotor in Place EFFECT Distributed capacitance of the feeder cable loads down the test according to the approximate formula: C V max capable = V Tester Tester. ( ) C Tester C Cable According to the formula, as the capacitance of the cable increases, the maximum voltage capable decreases. The tester may be unable to generate the desired test voltage. Cable length is recommended to be less than 100 feet. It is observed that the closer the motor is to the recommended maximum motor size to test, the shorter the feeder cable must be. If the motor is very small compared to the maximum recommended motor to test, the tester may have sufficient energy such that longer feeder cables as well as the motor windings, can be tested. The above condition becomes extreme. Shielded feeder cable has very high capacitance. Feeder cable lengths of less than 50 feet are recommended if attempting to test from the Motor Control Center (MCC). The characteristics of these motors are such that the winding impedance is low, requiring high tester output energy to surge test the windings. Select a tester based on the maximum recommended AC motor to test which will cover the horsepower rating of the motor, then go up one model in maximum tester output voltage. Generally requires testing at the motor, or if from the MCC, very short feeder cable length. The Power Pack option may be necessary. The presence of the rotor will load the tester by drawing energy from the tester like the secondary of a transformer User s Manual Do not touch test leads while test is in progress! Rev. C(11)-7/99

56 Surge Testing Notes for Surge and Surge Comparison Tests Sometimes full output of the tester may be below its rated maximum output voltage. This occurs on low impedance devices or devices which are too large for a tester s capability. For example, a motor may be of too high horsepower for a surge tester. A12,000 V tester may only apply 4000 V when the OUTPUT is set halfway between MIN and MAX when 6000 V is expected. Subsequently the tester may then only impress 7000 V at MAX when 12,000 V is expected. When encountering this condition, call Baker Instrument Company for assistance. Some test tips may be available to overcome this limitation. Also see Factors Affecting the Surge Tester s Output on page The test should be considered successful if the desired test voltage level can be reached. For the example above, if the motor is 3000 horsepower and operated at 2300 V, a recommended test voltage would be 2 x 2300 V V= 5600 V. The size of the motor limits the tester s output below its rating, but an appropriate test voltage (above 5600 volts) can be reached. Adjacent windings such as a start winding, part winding, high or low-voltage winding should be jumpered together and grounded during testing. This procedure eliminates incorrect test results caused by inductive coupling. Do not touch test leads while test is in progress! User s Manual 6-13 Rev. C(11)-7/99

57 Surge Testing Determination of a Fault There are only five main wave patterns to remember which are obvious from an understanding of the test. These are: Good, stable trace, indicating adequate winding or phase insulation; Instability, indicating weakness in the winding insulation and intermittent arcing between windings or phases; Separation when compared to another wave pattern, indicating a fault on a winding or phase insulation; Open circuit, and; Grounded winding. Memorization of wave patterns should not be necessary to determine if a winding is good or bad. For more detailed discussions on particular faults, refer to Section 7: Surge Test Applications. NOTE: If all three wave pattern comparisons in surge testing show considerable separation when testing three phase windings, the motor has a PHASE- TO-PHASE short. Good, Stable Trace The winding is considered good if a pair of wave patterns compare by superimposing and remain stable up to the specified test voltage. STORE RECALL PRINT RECALL Record 1 Lead V/div 2 us/div CLEAR Peak: 1500 V Pulse: V/div SURGE 2 us/div Two wave patterns for a good winding or coil superimpose exactly User s Manual Do not touch test leads while test is in progress! Rev. C(11)-7/99

58 Surge Testing Instability If the wave pattern begins to flicker or rapidly shift left and right and/or up and down as the OUTPUT is increased, there is weakness in the winding insulation and intermittent arcing between the windings or phases. The winding or phase contains a fault when the wave pattern shifts to the left and the amplitude drops. The more severe the shift and amplitude drop, the more severe the fault. These faults are often accompanied by an audible arcing sound. STORE RECALL PRINT CLEAR Peak: 1500 V Pulse: 5 Display rapidly shifts between wave patterns 500 V/div SURGE 2 us/div Representation of how a live wave pattern may move on the display for a winding or coil that is arcing NOTE: The flicker or shifting in wave patterns observed when there is arcing between the windings or phases cannot be stored in the Digital tester. As soon as the TEST button is released, the wave pattern freezes. This is the only wave pattern that can be stored. It is desirable to store the wave pattern produced by this arcing for reference. The operator must attempt to release the TEST (thus freezing the wave pattern for storage) at the moment when the wave pattern appears the most affected by the fault (reduced amplitude and greater frequency). STORE RECALL PRINT RECALL Record 1 Lead V/div 2 us/div Arcing CLEAR Peak: 1500 V Pulse: 8 Good 500 V/div SURGE 2 us/div Example of what an unstable wave pattern for an arching winding or coil MAY look like when stored on the Digital Tester and compared to a good winding. Do not touch test leads while test is in progress! User s Manual 6-15 Rev. C(11)-7/99

59 Surge Testing Separation When Compared to Another Wave Pattern If a single phase in a three phase motor is faulted, separation of the wave patterns when they are compared in pairs will appear in two out of three comparisons. The location of the faulty phase can be determined by these comparisons. The final determination of where the fault lies depends on how the phases are connected together. There are two ways three-phase motors are connected. These are termed wye-connected and delta-connected and are discussed below. Wave Pattern Separation for Wye-Connected Motors In wye-connected motors, the test lead which shows separation is the test lead connected to the faulty phase. For example, if wave comparisons 1-2 and 2-3 indicate a fault, the bad phase is connected to test lead 2. The figures below exemplify this. Wave comparisons 1-2 and 2-3 show differing wave patterns, while wave comparison 3-1 shows identical patterns for the two leads. The fault must be in the phase connected to test lead 2. In other words, wave comparison 3-1 shows superimposing wave patterns because the bad phase was not connected to these leads but was instead held at ground. STORE RECALL PRINT CLEAR STORE RECALL PRINT CLEAR RECALL Record 1 Lead V/div 2 us/div RECALL Record 1 Lead V/div 2 us/div Peak: 1500 V Pulse: 5 Peak: 1500 V Pulse: V/div SURGE 2 us/div 500 V/div SURGE 2 us/div Comparison of #1 - #2 and #2 - #3 Comparison of #3 - #1 Example of a Surge Test Comparison where there is a fault in lead #2 1 shows NO fault shows fault 3 2 shows fault 6-16 User s Manual Do not touch test leads while test is in progress! Rev. C(11)-7/99

60 Surge Testing The following chart details this principle for a wye-connected motor. Fault Location for Wye-Connected Three Phase Motors PHASE PAIR WAVE PATTERN PHASE 1 PHASE 2 PHASE SINGLE DOUBLE DOUBLE DOUBLE SINGLE DOUBLE DOUBLE DOUBLE SINGLE GOOD GOOD FAULTY GOOD FAULTY GOOD FAULTY GOOD GOOD Wave Pattern Separation for Delta-Connected Motors NOTE: Because the surge test applied to delta-connected windings is testing phases that are in parallel paths, a single turn-to-turn short, open condition, or short to ground within these paths can be difficult to detect. It is recommended that the leads be separated and the windings be tested individually or in a wye-connect pattern. This will provide the greatest sensitivity for finding a turn-to-turn short. Baker Instrument Company recommends disconnecting the windings at 1 & 4, 2 & 5, and 3 & 6. Use the Digital tester to surge test each individual phases as you would for testing single coils. Refer to Single Coil Surge Test and Set-Up on page 6-3 for test procedures and analysis In delta-connected motors, the faulty phase winding is terminated by the leads which produce wave patterns that show the greatest amount of separation when compared. All three possible surge test wave pattern comparisons will show varying degrees of separation. The wave pattern for any given TLS position represents the lead numbers terminating the ends of two phase windings. The winding fault will be located in the phase between the leads whose wave patterns are the MOST speparated when compared. Consider the example illustrated by the figure below. 1 C A Comparison of 1-2: Moderate Separation Comparison of 2-3: Greatest Separation Comparison of 3-1: Least Separation 3 B 2 Fault in winding B terminated by leads 2 and 3 Do not touch test leads while test is in progress! User s Manual 6-17 Rev. C(11)-7/99

61 Surge Testing In this example, the fault lies in phase winding B which is terminated by leads #3 and #2. Consider a surge impulse applied to lead #1. The voltage takes two paths. One path goes through winding A which contains no faults. The other path goes through C which is good and B which is faulty. The wave pattern will be only slightly affected by the fault. Next, an impulse is applied to lead #2. One path goes through winding B which contains the fault. The other path goes through A and C which are both good. The wave pattern will be greatly affected by the fault. OPEN C GROUND HOT A B OPEN C B GROUND A HOT In a similar way, the impulse applied by testing lead #3 travels through winding C which contains no fault. The other path goes through B which is faulty and A which is good. The wave pattern will be moderately affected by the fault. GROUND C A HOT B OPEN The following chart provides a guide for determining the location of a winding fault in a delta-connected motor with phases and lead connections set as in the example above. Winding Fault Location for Delta-Connected Three Phase Motors LEADS BEING COMPARED PHASES BEING COMPARED DEGREE OF SEPARATION FAULT LOCATION A & C,B B & A,C B & A,C C & B,A C & B,A A & C,B Greatest Least Moderate Phase A A & C,B B & A,C B & A,C C & B,A C & B,A A & C,B Least Moderate Greatest Phase C A & C,B B & A,C B & A,C C & B,A C & B,A A & C,B Moderate Greatest Least Phase B 6-18 User s Manual Do not touch test leads while test is in progress! Rev. C(11)-7/99

62 Surge Testing Open Circuit Open circuit indications are almost always the same for wye and delta-connected motors. For each, an open circuit is indicated when the wave pattern is elevated and there is no ringing. This occurs due to the loss of a complete circuit between the hot lead and the ground return. NOTE: If an open circuit condition is indicated, check the connections between all three test leads and the device under test and the clip ends. Test leads should be checked weekly to ensure there is no breakage! Test leads are easily checked for breakage by firmly grasping the boot and clip in one hand while pulling on the lead with the other. A broken lead will stretch a good lead will not stretch. Open Phase in Wye-Connected Motors In the case of an open phase in a wye-connected motors, the wave patterns are illustrated below. When an open phase exists a pattern resembling a ski ramp is seen because there is a total loss of continuity throughout the tested winding. This pattern is also seen when nothing is connected to the surge test leads. STORE RECALL PRINT RECALL Record 1 Lead V/div 2 us/div CLEAR Peak: 1500 V Pulse: 11 STORE RECALL PRINT RECALL Record 1 Lead V/div 2 us/div CLEAR Peak: 1500 V Pulse: V/div SURGE 2 us/div 500 V/div SURGE 2 us/div Comparison of #1 - #2 and #2 - #3 Comparison of #3 - #1 Example of a Surge Test Comparison of a wye-connected motor where there is an open phase in lead #2 Do not touch test leads while test is in progress! User s Manual 6-19 Rev. C(11)-7/99

63 Surge Testing Open Phase in Delta-Connected Motors An open phase in a delta-connected motor is always in parallel with another winding. Because the windings are necessarily tested in parallel, the wave pattern signatures are higher in frequency than in wye motors. When an open phase exists, two wave patterns will superimpose when they are compared. The third wavepattern will be shifted to the right due to higher inductance in the phases connected to that lead, one of which contains the open condition. The open condition will be located between the lead whose wave pattern has shifted and the next lead in the test progression. Refer to the illustration used above in Wave Pattern Separation for Delta- Connected Motors on page 6-17, but consider an open condition located in the same position as the winding fault. The wave patterns for leads #1 and #3 will compare exactly because one phase will be surged in each case ( A and C respectively). The wave pattern for lead #2 will shift to the right because two phases in series ( A and C ) will be surged in this case. The open exists in phase B because it is terminated by lead #2, which shows the fault, and the next lead in the progression which is lead #3. The following chart provides a guide for determining the location of an open phase in a delta-connected motor with phases and lead connections set as in the example above. Open Condition Location for Delta-Connected Three Phase Motors LEADS BEING COMPARED PHASES BEING COMPARED WAVE PATTERN OPEN LOCATION A & C,B B & A,C B & A,C C & B,A C & B,A A & C,B Double Single Double Phase A A & C,B B & A,C B & A,C C & B,A C & B,A A & C,B Single Double Double Phase C A & C,B B & A,C B & A,C C & B,A C & B,A A & C,B Double Double Single Phase B 6-20 User s Manual Do not touch test leads while test is in progress! Rev. C(11)-7/99

64 Surge Testing Grounded Winding A hard short to ground can be detected when surge testing. Grounded windings in both wye- and delta- connected motors will also be detected by the DC Hipot test (refer to Section 5: DC Hipot Test). Hard Short to Ground In surge testing, one trace will show a relatively flat line. For both wye- and deltaconnections the hard short to ground will be in the test lead that shows a flat line instead of a wave pattern. STORE RECALL PRINT RECALL Record 1 Lead V/div 2 us/div CLEAR Peak: 1500 V Pulse: 6 STORE RECALL PRINT RECALL Record 1 Lead V/div 2 us/div CLEAR Peak: 1500 V Pulse: V/div SURGE 2 us/div 500 V/div SURGE 2 us/div Comparison of #1 - #2 and #2 - #3 Comparison of #3 - #1 Example of a Surge Test Comparison where there is hard short to ground in lead #2 Do not touch test leads while test is in progress! User s Manual 6-21 Rev. C(11)-7/99

65 Surge Testing Partial Short to Ground in Wye-Connected Motors Partial shorts within the phase winding in wye-connected motors will result in a damped, left shifted wave pattern when surge testing. The exact location of an open phase in wye-connected motors can be determined in a manner similar to the methods found in Wave Pattern Separation for Wye-Connected Motors on page STORE RECALL PRINT RECALL Record 1 Lead V/div 2 us/div CLEAR Peak: 1500 V Pulse: 5 STORE RECALL PRINT RECALL Record 1 Lead V/div 2 us/div CLEAR Peak: 1500 V Pulse: V/div SURGE 2 us/div 500 V/div SURGE 2 us/div Comparison of #1 - #2 and #2 - #3 Comparison of #3 - #1 Example of a Surge Test Comparison of a wye-connected motor where there is a partial ground in lead #3 Partial Short to Ground in Delta-Connected Motors The location of short to ground in a delta-connected motor is determined in a manner exactly as for locating a shorted turn fault in the winding. The short to ground is terminated by the leads which produce wave patterns that show the greatest amount of separation when compared. Refer to the illustration and table in Wave Pattern Separation for Delta-Connected Motors on page User s Manual Do not touch test leads while test is in progress! Rev. C(11)-7/99

66 Section 7 Surge Test Applications This chapter describes test methods and fault determination for the following types of devices and apparatus: Maintenance Testing (page 7-2) Single Phase Motors and Two Terminal Devices (page 7-4) Form Coils (page 7-5) Three Phase Motors (page 7-6) Two or More Single Coils (page 7-7) Wound Rotor Motors (page 7-9) Synchronous Motor/Generator (page 7-10) DC Motor/Generators (page 7-11) Field Coils (page 7-11) Chiller Motor Testing (page 7-11) Armatures (page 7-12) Testing Large AC Stators/Motors (page 7-16) Rotor Loading (Coupling) when Testing Assembled Motors (page 7-17) Testing Assembled Motors from the Switchgear (page 7-19) Transformers (page 7-20) For additional reference for fault determination, see Appendix A: Typical Winding Faults. NOTE: If all three wave pattern comparisons in surge testing show considerable separation when testing three phase windings, the motor has a PHASE- TO-PHASE short. Do not touch test leads while test is in progress! User s Manual 7-1 Rev. C(13)-7/99

67 Surge Test Applications Maintenance Testing Baker Instrument Company Surge Testers have become extremely popular for industrial maintenance programs, troubleshooting, and to ensure that replacement motors (spares, reconditioned motors, or rewinds) are thoroughly tested. The following are guidelines for performing surge tests on assembled motors in the field as part of maintenance testing. Hard-shorted winding faults are rarely found in motors during maintenance testing. Solid turn-to-turn winding faults happen when the insulation on adjacent copper wires has failed to the point that adjacent wires are welded together. It is arare condition in maintenance testing because of a transformer action which occurs within the windings which induces very high current in a hard turn-to-turn short. The high current causes heating and deterioration of the surrounding insulation systems. The single turn-to-turn short rapidly compounds until the damage causes a failure in the ground wall insulation. The high current will trip the circuit breaker and stop the motor. A solid turn-to-turn, or hard-shorted winding fault is not the type of fault to expect to see during maintenance testing. This condition is usually only found after the motor has failed. During surge testing, steady separation in the wave pattern comparisons is most often the result of the rotor coupling with the stator. (See Rotor Loading (Coupling) when Testing Assembled Motors on page 7-17.) In this case, a consistent double wave pattern will be seen at all voltage levels. Separation due to rotor coupling should not be interpreted as a fault. The key to the surge testing for maintenance is to detect a fault at a voltage level above the peak operating voltage but not above what the motor would withstand during start-up. For example, a 460 V motor that shows a good trace at 500 V but shows an unstable, flickering pattern (regardless of rotor coupling) at 1500 V definitely contains a fault. When the fault is detected above operating voltage, time is available to schedule service for the motor before a hard short and rapid failure occurs. Consider a 460 volt AC motor. The operating voltage is the root mean square, akind of average, of the AC power supply. For this motor, multiply 460 volts by 1.4 to determine the maximum voltage level that the coil undergoes during normal operation. It is approximately 650 volts. Suppose the motor has an insulation fault at 500 volts. This motor will probably fail while in service well before it can be surge tested because the peak of the AC voltage will continuously stress the fault under normal operating conditions. The goal, therefore of the surge test is to detect weakness well above the operating voltage of the motor, as much as twice the operating voltage plus 1000 volts. Refer to Recommended Voltages on page 4-3 for a thorough description of how to determine test voltages along with IEEE references that explain the reasons for these recommendations. 7-2 User s Manual Do not touch test leads while test is in progress! Rev. C(13)-7/99

68 Surge Test Applications As shown in the figures below, a good winding will produce stable wave patterns from zero volts up to the recommended test voltage. Faults will be detected during surge tests as unstable, flickering wave patterns that appear as the voltage is increased. STORE RECALL PRINT CLEAR STORE RECALL PRINT CLEAR Peak: 1500 V Pulse: 6 Peak: 1500 V Pulse: 6 Display rapidly shifts between wave patterns 500 V/div SURGE 2 us/div 500 V/div SURGE 2 us/div Good wavepattern (left) and a representation of how a live wave pattern may appear to move on the display for a winding or coil that contains an intermittent short or is arcing (right). Application Notes If an open circuit condition is indicated, check the connections between all three test leads and the device under test. Check for open test leads at the clip end. With heavy use test leads should be checked weekly to ensure there is no breakage. Test leads are easily checked by firmly grasping the boot and clip in one hand while pulling on the lead with the other. A broken lead will stretch. A good lead will not stretch. STORE RECALL PRINT RECALL Record 1 Lead V/div 2 us/div CLEAR Peak: 1500 V Pulse: V/div SURGE 2 us/div Open phase in lead in a wye-connector motor Do not touch test leads while test is in progress! User s Manual 7-3 Rev. C(13)-7/99

69 Surge Test Applications Single Phase Motors and Two Terminal Devices Select TLS #1 and connect the corresponding test lead #1 to one side of the device. Connect test lead #2 to the opposite side of the two terminal device. Connect the ground lead and test lead #3 of the tester to the frame or metal core material. Determination of a Fault If a fault exists in a single phase motor or two terminal device, the wave pattern on the display will collapse in amplitude and a distinct shift to the left will occur, signifying an increase in frequency (a decrease in inductance). When inductance decreases, the frequency of the wave pattern will increase according to the formula 1 Frequency = π LC This is illustrated in the figure below. This type of fault is generally one that indicates a failure of the turn-to-turn insulation. STORE RECALL PRINT CLEAR STORE RECALL PRINT CLEAR Peak: 1500 V Pulse: 6 Peak: 1000 V Pulse: V/div SURGE 2 us/div Good coil 500 V/div SURGE 2 us/div Bad coil If any wave pattern becomes erratic and/or flickers during testing, intermittent shorting or arcing is probably occurring in the windings under the voltage stress. Arcing is often accompanied by audible sounds. It may be desirable to store the wave pattern produced by this arcing for reference if the operator can release the TEST (this freezes the wave pattern) at the moment when the wave pattern appears the most affected by the fault (reduced amplitude and increased frequency or shift to the left). 7-4 User s Manual Do not touch test leads while test is in progress! Rev. C(13)-7/99

70 Surge Test Applications Form Coils Form coils should be tested similarly to a two terminal device (see Single Phase Motors and Two Terminal Devices on page 7-4). The Surge test is recommended for form coil testing because it alone can generate the turn-to-turn voltage stress that is required in these low impedance coils. Determination of a Fault Refer to the previous section on Single Phase Motors and Two Terminal Devices on page 7-4 to determine if a fault is present. Notes and Tips for Form Coils IEEE recommends a test voltage for Vacuum Pressure Impregnation coils, before they are cured, of percent of the test voltage of fully cured coils. Currents required to test form coils often limit the maximum surge voltage. Placement of the coils into the stator iron or spare laminations has the effect of enabling the tester to produce a higher voltage drop across the coil for a given current level. CAUTION should be exercised since the laminations or stator core have induced voltage on them, and can provide a path to ground. Many formulas are used in calculating a test voltage for AC form-wound coils. These are generally based on experience and theoretical arguments about the distribution of voltage in a coil and the entire winding. Some of these formulas are difficult to apply because of the great diversity of coil specifications and characteristics. One popular formula (based on Paschen s Law, page 7-8) states a minimum and maximum test voltage range: Minimum = Number of turns x 500 Volts Maximum = Winding operating voltage x 1.5 The minimum voltage would be necessary to show a void in the turn insulation that would result in arcing. The maximum voltage value is based on the worst case distribution of a surge in the winding. Studies (IEEE and IEEE ) have shown that a very rapid surge from a lightning strike or contactor closing/opening may be distributed across the first coil of a winding. Do not touch test leads while test is in progress! User s Manual 7-5 Rev. C(13)-7/99

71 Surge Test Applications Three Phase Motors Wave patterns for three phase windings are compared in pairs. The storage capabilities of the Digital Tester allow all three phases to be compared without removing and reconnecting the test leads. The operator simply recalls any one of the previously tested leads. Baker Instrument Company recommends the following procedure: 1. Connect the three numbered RED test leads to the three winding legs. 2. Connect the BLK GRD lead to the frame or core of the winding. 3. Begin with the TLS in position #1. This indicates lead #1 will be hot while leads #2 and #3 provide a ground path for the surge impulse. 4. Perform the test as described in Three Phase Motor Surge Test and Set-Up on page 6-6. For each test, you will have checked the display for a wave pattern. Recall a SUMMARY from the digital tester s memory the wave patterns for the motor for comparison. If you see three good wave comparisons, there is every indication to believe the motor is good. If you have seen anything other than good patterns there is a possible fault. Determination of a Fault If any wave pattern becomes erratic and/or flickers during testing, intermittent shorting or arcing is probably occurring in the windings under the voltage stress. Arcing is often accompanied by audible sounds. It may be desirable to store the wave pattern produced by this arcing for reference if the operator can release the TEST (this freezes the wave pattern) at the moment when the wave pattern appears the most affected (reduced amplitude and increased frequency or shift to the left). Separation in two of three wave pattern comparisons indicate incorrect turns count. The fault will be in the phase connected to the test lead in common between the two comparisons which show the separation for wye-connected windings. IN THE REPAIR SHOP: Separation of compared wave patterns on STATORS indicates a hard fault, such as a solid turn-to-turn or group-to-group short, an incorrect turns count, or misconnections. IN THE FIELD: In ASSEMBLED MOTORS, separation of the wave patterns is often the effect of ROTOR COUPLING, also known as rotor loading (see Rotor Loading (Coupling) when Testing Assembled Motors on page 7-17). 7-6 User s Manual Do not touch test leads while test is in progress! Rev. C(13)-7/99

72 Surge Test Applications Two or More Single Coils Surge testing can be used to test two or more identical single coils separately and then compare their wave patterns against each other. 1. Connect test lead #1 to one side of coil #1 and connect the ground test lead to the other side. 2. Connect test lead #2 to the second coil or identical coils and connect test lead #3 to that coil s other side. 3. Surge test the first coil with the TLS in position #1. Store the results in memory. NOTE: Use QUICK STORE for a fast determination of the results of this test. 4. Surge test the second coil or any number of identical coils with the TLS in position #2. (Store the result(s) if desired.) If the wave patterns are stable and they superimpose on the display, the two windings are identical. They have no faults and the insulation of both coils is good. Determination of a Fault If any wave pattern becomes erratic and/or flickers during testing, intermittent shorting or arcing is probably occurring in the windings under the voltage stress. Arcing is often accompanied by audible sounds. It may be desirable to store the wave pattern produced by this arcing for reference if the operator can release the TEST (this freezes the wave pattern) at the moment when the wave pattern appears the most affected (reduced amplitude and increased frequency or shift to the left). Separation of the wave patterns when compared indicates incorrect turns count. The fault will be in the coil connected to the test lead which produces the wave form most shifted to the left and collapsed in amplitude. Notes and Precautions for Two Single Coils All windings or magnetic material (iron or ferrite) close to the coils under test MUST be the same for both coils. For example, if DC field coils are being tested, both should have the pole pieces inserted or both removed. A coil on a table when compared to an identical coil in the frame will show separation of the wave patterns because inductance differs in iron and air. Slight variations in magnetics of the tested device can result in similar coils not comparing identically. An example of this is synchronous pole pieces, one of which is making better magnetic contact with the rotor than the comparing pole. For this reason it is recommended that devices like pole pieces be evaluated individually and NOT compared. Do not touch test leads while test is in progress! User s Manual 7-7 Rev. C(13)-7/99

73 Surge Test Applications Paschen s Law states that a voltage greater than 335 volts is required to initiate an arc between two conductors in air. This would suggest a minimum voltage for surge testing to be greater than 335 volts. Because of the sometimes non-linear distribution of the surge pulse, it is recommended that aminimum surge potential of 500 volts be used when testing a two terminal device. Shunt coils often have a small error in turns count. Some mismatch or separation ofpatterns should be acceptable. If the wave patterns are very close in shape and remain STABLE during the test, the coils generally are acceptable. In addition, winding tolerances on single coils may allow for differences in turns count which causes a slight, steady separation. The operator should investigate whether this condition is acceptable or not. A slight imbalance (separation) may be noticed if the windings are not correctly phased: i.e. the winding configuration of one compared to another is clockwise verses counterclockwise. Try reversing one set of test lead connections and repeating the test before rejecting the winding. Many two terminal devices have very high turns count. The waveform displayed is similar to that of an OPEN circuit. In this case, the impedance of the coil is too high to be tested. Double check for poor connections and test lead breakage to see if these conditions may be causing the apparent open condition. 7-8 User s Manual Do not touch test leads while test is in progress! Rev. C(13)-7/99

74 Surge Test Applications Wound Rotor Motors Wound rotor motors are tested as though they are two separate three phase windings where one is the stator and the other is the rotor. Procedures to successfully test the wound rotor motor are as follows. 1. Remove the brushes touching the slip rings. 2. Short together the slip rings with jumpers. The jumpers minimize the coupling effect between rotor and stator. 3. Surge test the stator as would be done on a three phase induction motor. See Three Phase Motors on page 7-6 or follow the directions in Three Phase Motor Surge Test and Set-Up on page 6-6. NOTE: Since the rotor is shorted out there will be no chance for a high induced voltage transformed from the stator to damage the rotor. 4. To surge test the rotor, disconnect the jumpers from the slip rings. Connect the tester test leads to the rotor slip rings. 5. Short together the stator leads with jumpers, as done for the rotor. 6. Repeat Step 3 for the rotor. NOTE: Check the motor name plate for rotor voltage to calculate the rotor test voltage level. Rotor voltage is NOT THE SAME as the stator voltage. If the wave patterns are stable and they superimpose on the display, the windings are identical. They have no faults and the insulation of both coils is good. Determination of a Fault If any wave pattern becomes erratic and/or flickers during testing, intermittent shorting or arcing is probably occurring in the windings under the voltage stress. Arcing is often accompanied by audible sounds. It may be desirable to store the wave pattern produced by this arcing for reference if the operator can release the TEST (this freezes the wave pattern) at the moment when the wave pattern appears the most affected (reduced amplitude and increased frequency or shift to the left). Separation of the wave patterns when compared indicates incorrect turns count. Interpret the separations as for three phase motors. Do not touch test leads while test is in progress! User s Manual 7-9 Rev. C(13)-7/99

75 Surge Test Applications Synchronous Motor/Generator The synchronous stator is tested as a three phase induction motor. The rotating fields should be tested individually. 1. Before surge testing the stator: a. Remove the DC leads to the brush boxes or lift all of the brushes off the slip rings. b. Short the slip rings for the rotating fields together. 2. Surge test the stator following the procedures and steps for Three Phase Motors on page Individual poles are surge tested as outlined in the procedures for testing Single Phase Motors and Two Terminal Devices on page 7-4. The recommended test voltage is 600 volts per pole. It is not necessary to disconnect the pole piece leads before testing. 4. The HOT and GROUND leads are then reversed and the test repeated on each coil. If the wave patterns are stable and they superimpose on the display, the windings are identical. They have no faults and the insulation of both coils is good. NOTE: One field can be tested and its surge wave pattern can be stored for reference. The other fields can then be compared to this reference pattern in a procedure that is similar to that of Two or More Single Coils on page 7-7. Determination of a Fault Two types of faults may exist in synchronous motors and generators. Pole Piece Fault Do not expect coils to compare exactly. Rotating fields or pole pieces are often not wound to identical, exacting standards. If a fault does exist in the pole pieces during the test, the wave pattern on the display will collapse in amplitude and a distinct shift to the left will occur, signifying an increase in frequency (a decrease in inductance). This type of fault is usually failure of the turn-to-turn insulation. Stator Winding Fault For a stator winding fault, if the wave pattern changes and becomes erratic during the test, then intermittent shorting or arcing is occurring in the winding under test. Steady separation of the wave patterns of the phases when recalled and compared indicates solid shorts. (See Three Phase Motors on page 7-6.) 7-10 User s Manual Do not touch test leads while test is in progress! Rev. C(13)-7/99

76 Surge Test Applications Chiller Motor Testing Before applying any test potential to a chiller motor, please review the manufacturer s instructions. These instructions usually recommend bleeding the vessel to atmospheric pressure before applying a test potential. Surge test procedures for chiller motors follow those outlined for Three Phase Motors on page 7-6. Field Coils When testing field coils follow the procedures outlined for testing Single Phase Motors and Two Terminal Devices on page 7-4 and Synchronous Motor/ Generator on page The recommended surge test voltage for DC fields is 600 volts. If the impedance of the coils is very low (few turns count, generally form coils with very low resistance) the surge tester stand-alone may not adequately test the coils. A bar-to-bar, low impedance test accessory from Baker Instrument Company will be necessary. DC Motor/Generators While the series or shunt fields of the DC motor/generator are tested as a two terminal device, the armature may be tested by three different methods. A short armature testing video is available at no charge from Baker Instrument Company. Do not touch test leads while test is in progress! User s Manual 7-11 Rev. C(13)-7/99

77 Surge Test Applications Armatures Bar-to-Bar Surge Test Span Testing There are two methods of Surge testing armatures: the BAR-TO-BAR surge test and the SPAN surge test. The use of a FOOTSWITCH is highly recommended to ease the operation of these tests. Bar-to-bar armature surge testing is the most effective method to test DC armatures and detect winding insulation weakness and faults. In many cases, where the impedance of the coils in the armature is very low, it may be the only method possible to test the armature. To perform bar-to-bar Surge testing, the Model AT101D Bar-to-Bar Testing Accessory is necessary. Bar-to-bar testing instructions accompany the AT101D and can be found in Appendix E: Model AT101D Bar-to-Bar Armature Test Accessory is this manual. This method uses the brushes of the assembled DC motor to make the connections with the commutator for testing of the armature. Any number of bars can be used in this test. Either adjacent bars can be surge tested or a specific number, or span of bars, can be tested. The number of bars tested in each span for an individual motor must be the same during the entire test. In the repair shop, a fixture can be used in place of the motor s brushes (refer to Notes and Tips for Span Testing Armatures on page 7-14). test lead #3 OPEN test lead #2 GROUNDED test lead #1 HOT Span Test using the motor s brushes The wave pattern produced in this test represents the voltage oscillation between the tester and the coils for the specific number of commutator bars spanned. For example, any 10 bars spanned in series on the armature should give the same pattern as any other 10 bars spanned. As the armature is rotated, all the commutator segments and therefore their respective coils, pass into the test area between the HOT surge test lead and the GRD lead User s Manual Do not touch test leads while test is in progress! Rev. C(13)-7/99

78 Surge Test Applications NOTE: It is important that the same number of bars (and therefore coils) always be in the test area. The test wave pattern for each span should match a reference wave pattern on the display for the complete armature if the coils are all good. 1. Remove all brush pig tail connections from the leads at the brush rigging for all sets of brushes to isolate the armature from the power source. 2. With the TLS switch in the LEADS GROUND position, connect test lead #1 to one of the brush assembly pigtails. Connect the GRD test lead to the shaft or other good ground on the frame. NOTE: When testing armatures that have bars that are wired in series, it is very important to ground at least two bars of the armature a few bars away from those that are being surged. If this is not done, very high potential voltages to ground can develop in the armature due to a transformer effect in the coils. 3. Select the adjacent set of brushes or the brushes of the bar corresponding to the desired span. Connect test leads #2 and #3 to the pigtail of that brush assembly. 4. Select the TLS position #1. Be sure the FUNCTION switch is set at SURGE. 5. Begin the test by pressing the TEST button or FOOTSWITCH and slowly raise the OUTPUT control to the desired test voltage level. Carefully observe the wave pattern for its reference shape. 6. Store this wave pattern as the reference wave pattern for this span on this particular armature. Recall the reference wave pattern to the display. (Use QUICK STORE if desired.) Note the peak voltage displayed on the screen. 7. Begin testing again using the same OUTPUT voltage until the test wave pattern matches the reference wave pattern. NOTE: The Zero Start Interlock is disabled only when the FUNCTION switch is set to AT101 for the AT101D accessory (see Appendix E: Model AT101D) and the FOOTSWITCH is depressed. Without the accessory andafootswitch, the OUTPUT must be turned back to zero or MIN and then brought back up to the peak voltage value noted above in Step 6. The same test voltage must be used for each span tested. 8. Rotate the armature slowly through 360 degrees so that all commutator segments are tested while observing the reference wave pattern. NOTE: It is recommended to release the TEST button (or FOOTSWITCH) each time the armature is turned, but it is not necessary. Doing so minimizes the chance of marking the commutator. If the TEST button or FOOTSWITCH is not released each time the armature is turned, the wave pattern will show regular shifts and flickers Do not touch test leads while test is in progress! User s Manual 7-13 Rev. C(13)-7/99

79 Surge Test Applications as the brushes move across one commutator bar to the next. This wave pattern movement should be ignored as long as the trace returns to the reference wave pattern and remains stable when the brushes are again centered on top of the bars. Determination of a Fault If the insulation is weak or failing on a particular bar or coil of the armature, the test wave pattern will become unstable and SHIFT LEFT when the section that contains the fault passes through the test area. The test wave pattern will no longer match the reference wave pattern. This indicates shorted windings within the tested span. Usually, as soon as the bad bar is placed under the hot brush, the wave pattern will show the shift to the left as noted above. Thus the bar directly below the hot brush is the faulty bar. An example of a fault found surge testing using the motor s brushes is illustrated below. STORE RECALL PRINT RECALL Record 1 Lead V/div 2 us/div CLEAR Peak: 1500 V Pulse: 14 STORE RECALL PRINT RECALL Record 1 Lead V/div 2 us/div CLEAR Peak: 1500 V Pulse: 14 Reference 500 V/div SURGE 2 us/div Fault located under the ground brush or outside of the surge test span 500 V/div SURGE 2 us/div Fault grounded under the hot brush Notes and Tips for Span Testing Armatures A test fixture can be used in place of using the motor s brushes to make contact with the armature. Set the span between the fixture s brushes to the desired number of commutator bars. Either the fixture can be moved around the commutator during testing, or the armature can be rotated. Procedures for testing and fault determination are the same. Always Hipot the armature to ground first. This gives an upper limit for the maximum voltage to apply when surge testing. The greater the span surge test voltage is, the more adequate the stress between bars is (ideally, 335 volts according to Pashen s Law). Voltage stress 7-14 User s Manual Do not touch test leads while test is in progress! Rev. C(13)-7/99

80 Surge Test Applications is measured by the differential or drop between each bar. For example, a 10 bar span with 1000 volts applied to it will result in a 100 volt stress between bars. If the span is lowered to 5 bars, 1000 volt applied to the span will result in 200 volts between bars. Consider, however, that a ten bar span at 335 Volts between bars would require a span test voltage of 3350 volts. This potential to ground at the first coil may be too high. A lower span test voltage is recommended if, for instance, the Hipot test was only to 2200 Volts. It is advantageous to keep the span as low as possible to still get a reasonably good ringing wave on the display. However, lowering the span reduces the resistance and inductance of the load under test. The low inductive load may cause difficulty achieving the desired test voltage and a good ringing wave pattern on the screen. To simulate a fault, use an insulated screwdriver to temporarily short two commutator bars together that are in the test area. This shows the response of the wave pattern when a fault exists. It gives an indication of what the user should expect to see. Equalizer windings can separate the test wave pattern from the reference pattern seen during span tests. Thus, a good armature winding can appear to be bad. For example, a wave pattern for 7 bars spanned may sometimes match that for 11 bars spanned. In addition, the patterns may show a rhythmic shift consistently throughout the 360 degrees of rotation, (for instance, as the armature or fixture is rotated, every third bar shifts left a little), which is not afault. This is due to the equalizers and does not indicate faulty windings. Releasing the TEST button or the FOOTSWITCH before moving to the next bar during the test minimizes the chance of marking the commutator. Do not touch test leads while test is in progress! User s Manual 7-15 Rev. C(13)-7/99

81 Surge Test Applications Testing Large AC Stators/Motors Due to the physical non-symmetry of the input area, high capacitance, and inductance on some large AC high voltage machines, care must be exercised when evaluating the waveforms. The photos below show wave pattern comparisons for a typical 4160 V stator. The first wave pattern is produced when the SECONDS/DIV control (sweep rate) has been turned clockwise too far, expanding the display of the wave pattern. The sweep rate is set too fast. This wave pattern is actually the first half cycle of the full wave. Distortion is caused by the non-symmetrical, distributed capacitance in the input portion of the winding. STORE RECALL PRINT RECALL Record 1 Lead V/div 2 us/div CLEAR Peak: 1500 V Pulse: 6 STORE RECALL PRINT RECALL Record 1 Lead V/div 10 us/div CLEAR Peak: 1500 V Pulse: V/div SURGE 2 us/div SECONDS/DIV set too far CW 500 V/div SURGE 10 us/div SECONDS/DIV adjusted CCW To correct for this display condition turn the SECONDS/DIV control counterclockwise, slowing the sweep rate. The correct surge wave pattern will ALWAYS extend below the zero line. Observe the natural ringing to the RIGHT of the point where the wave pattern crosses the zero line in a positive (upward) direction. Good practice is to start with the SECONDS/DIV control turned to its counterclockwise limit to begin when testing high voltage AC machines. Notes and Tips for Large AC Stator/Motors Large AC motors with parallel windings may show little, if any separation of wave patterns when shorted or open windings are present. The inductance change caused by these faults is often not detectable. Instances have been noted where an end turn of a winding has a hole blown in it, and yet surge wave pattern comparisons show no separation. As a result, it is critical to perform a winding resistance test with a milliohmmeter or micro-ohmmeter whenever evaluating the condition of a motor winding. The surge test must be done on each of the parallel windings individually for the highest degree of fault sensitivity User s Manual Do not touch test leads while test is in progress! Rev. C(13)-7/99

82 Surge Test Applications Rotor Loading (Coupling) when Testing Assembled Motors When testing assembled motors, the rotor can influence the shape of the surge wave pattern. These influences are as follows: 1. Loss of wave pattern amplitude: The inductive loading of the rotor causes rapid dampening (little to no cycles of the ringing pattern) of the wave pattern. 2. Separated wave pattern comparisons for good windings: Imbalance in the inductive coupling between the rotor and stator winding causes the wave patterns of two good phases to appear separated when they are compared. By turning the rotor, this coupling effect can be balanced out so the wave patterns superimpose. Rotor loading can be understood when the rotor is considered as a secondary of a transformer. When one phase being surged has a different number of rotor bars under its stator windings than the other phase being surged and compared, there is a different transformer action existing for each phase. The wave patterns on the display indicate this difference by displaying separated wave patterns when they are compared. Not all motors exhibit this characteristic. It is most prevalent in smaller, high efficiency motors with small tolerance air gaps. Separation of wave patterns that are due to rotor coupling can be determined when the wave patterns separate from the first positive peak downward, cross one another at the bottom (first most negative point) and separate again as they go upward (positive). STORE RECALL PRINT RECALL Record 1 Lead V/div 2 us/div CLEAR Peak: 1500 V Pulse: 6 Reference and real-time superimpose STORE RECALL PRINT RECALL Record 1 Lead V/div 2 us/div CLEAR Peak: 1500 V Pulse: 6 Real-time (differs due to rotor position) Reference 500 V/div SURGE 2 us/div 500 V/div SURGE 2 us/div Wave pattern comparisons for motor with rotor in place The recommended procedure for testing assembled motors where rotor coupling may occur is as follows. Refer to Three Phase Motor Surge Test and Set-Up on page 6-6 for detailed instructions for surge testing and Section 3: Storage and Print Capabilities for discussions of the storage and recall functions. 1. Surge test phase #1 of the motor. Store and recall the wave pattern by using the QUICK STORE function. Do not touch test leads while test is in progress! User s Manual 7-17 Rev. C(13)-7/99

83 Surge Test Applications 2. Surge test phase #2 of the motor. During the test carefully turn the rotor until the wave pattern superimposes that of phase #1 on the display. Store the results in Lead 2 in memory. 3. Repeat Step 2 for phase #3. If the rotor cannot be turned, carefully observe the wave pattern as the test voltage is slowly raised. Watch for a sudden shift to the left, instability, or flickering which would indicate a winding fault. Many winding insulation failures will not be visible at low voltages but become apparent at a higher voltage. NOTE: Rotor coupling does not impede the surge impulse from stressing the turn-to-turn or phase-to-phase insulation. It only causes the rapid damping of the wave pattern. This rapid damping decreases sensitivity in interpretation of solid faults. Unstable, flickering wave patterns clearly indicate a fault in assembled motors whether rotor coupling is present or not. STORE RECALL PRINT RECALL Record 1 Lead V/div 2 us/div Reference (recalled) CLEAR Peak: 1500 V Pulse: 6 Real-time contains fault 500 V/div SURGE 2 us/div Motor with rotor in place and with faulty windings. One trace shifts significantly to the left User s Manual Do not touch test leads while test is in progress! Rev. C(13)-7/99

84 Surge Test Applications Testing Assembled Motors from the Switchgear The Surge and Hipot tests are valid tests when testing from the switchgear at the motor control center. Not only are the windings of the motor tested, but the insulation on the connections and feeder cables phase-to-phase and phase-toground are tested. Follow all the procedures for surge testing (refer to Section 6: Surge Testing). Keep in mind that different types and sizes of motors will give different traces, but the principle of testing assembled motors is still the same. When interpreting the wave patterns for good or bad windings, stability and symmetry are the most important factors. WARNING: THE MOTOR MUST BE DE-ENERGIZED BEFORE TESTING! Connect the test leads to only the load side of the open disconnect! Note and Tips for Testing from the Switchgear The test motor should be properly tagged during the test as a safety precaution. All of the limitations and guidelines covered for testing assembled motors apply here (see Rotor Loading (Coupling) when Testing Assembled Motors on page 7-17). Any power factor capacitors in the circuit must be disconnected. If power factor capacitors are present, no waveform will be observed when the voltage is raised. This will also happen if the motor was not connected to the cable. Only a rise in the trace on the far left will be noted. The surge test circuit will be loaded by the feeder cable capacitance as well as the motor. Significantly higher OUTPUT settings will be needed to reach the required test voltage. If the surge tester is too small to handle both the cable and the motor load, a trace will be observed but the proper test voltage will not be reached. A higher output surge tester model will be required or the motor may have to be tested while disconnected from the feeder cable. There is no precise science to determine what size motor, with what size and length feeder cable a particular surge test model can adequately test. In general, the closer the size of the motor is to the recommended maximum motor size for a given model surge tester, the shorter the cables can be and still allow testing at the required voltage. Conversely, the smaller the motor size, the longer the cable can be. Do not touch test leads while test is in progress! User s Manual 7-19 Rev. C(13)-7/99

85 Surge Test Applications Transformers Transformers contain similar insulation systems as motors: ground, turn-to-turn and phase insulation. However, the spectrum of winding characteristics for transformers is much broader than for motors. The Surge test is only one of many tests that should be performed to properly test a transformer. If the transformer has thousands of turns, the surge tester may not be sensitive enough to detect a single shorted winding. It may also sense the high inductance of a transformer as an open. The following testing procedures for single phase and three phase transformers provide the basics necessary to surge test transformers. Please call Baker Instrument Company at for further assistance or if difficulties are encountered when testing transformers. Single Phase Transformers 1. Jumper (or short out) the secondary side (low side) of the transformer. 2. Select TLS #1. Follow the diagram below to connect test lead #1 to H1 and test lead #2 to H2 of the transformer. The black GRD lead and test lead #3 go to the frame. test lead #1 H1 X jumper together test lead #2 H2 test lead #3 & black ground lead Single Phase Transformers connections 3. Surge test the winding following the procedures outlined for Single Phase Motors and Two Terminal Devices on page 7-4. The discussion of determining a fault applies. NOTE: Secondary winding insulation problems are reflected into the primary winding, and will be observed on the display. 4. After completing the test, reverse the test leads (connect test lead #2 to H1 and test lead #1 to H2) and repeat the surge test. This is commonly referred to as shooting it in the other direction. 5. Repeat this test procedure for each TAP position User s Manual Do not touch test leads while test is in progress! Rev. C(13)-7/99

86 Surge Test Applications Three Phase Transformers It is beyond the scope of this manual to cover all possible transformer connections. It is important to remember that each line high side connection point must be surge tested to the other end of its own coil, and that the secondary side of the coil being surged must be shorted out (jumpered together and to ground). NOTE: A wye-wye transformer with the star point internally tied can be surge tested without opening the tie point. 1. Use TLS position #1. 2. Connect the black ground test lead to the frame (ground) of the transformer. 3. Follow one of the charts below for connections for wye-wye or delta-wye transformers. The transformer windings should be surge tested for all the configurations shown. 4. Test procedures follow identically as for Single Phase transformer testing (refer to Single Phase Motors and Two Terminal Devices on page 7-4). Determination of a Fault The determination of a fault when surge testing a transformer winding follows that of the Two Terminal Device (refer to Single Phase Motors and Two Terminal Devices on page 7-4). Wye-Wye Transformers Test Lead #1 Test Lead #2 Jumper H1 H0 X0 TO X1 H2 H0 X0 TO X2 H3 H0 X0 TO X3 Delta-Wye Transformers Test Lead #1 Test Lead #2 Jumper H1 H2 X0 TO X2 H1 H3 X0 TO X1 H2 H1 X0 TO X2 H2 H3 X0 TO X3 H3 H2 X0 TO X3 H3 H1 X0 TO X1 Do not touch test leads while test is in progress! User s Manual 7-21 Rev. C(13)-7/99

87 Surge Test Applications 7-22 User s Manual Do not touch test leads while test is in progress! Rev. C(13)-7/99

88 Section 8 Additional Tests The Baker Instrument Company Digital Tester is capable of performing two tests in addition to DC Hipot and Surge tests. These are the Polarization Index and Step-Voltage tests. Polarization Index Test The Polarization Index (PI) test is useful for testing apparatus with complex insulation such as large motors and generators, where repeatable insulation resistance readings are difficult to obtain. This test measures the ratio between insulation resistance (IR) tests taken at one minute and ten minutes. The following formula is used to determine the Polarization Index. There are a number of advantages in using the Polarization Index test over a possibly ever-changing insulation resistance test. Temperature compensation is NOT necessary because you are comparing two resistance readings at the same temperature to determine the ratio. (See Resistance Temperature Compensation on page 5-7.) The PI test can determine insulation faults in larger test pieces with much more insulation than smaller test pieces. The PI test can indicate the presence of moisture or dirt in the winding s insulation. Determination of the Polarization Index only requires two measurements. Polarization Index Procedure IRat 10 minutes = Polarization Index (PI) IRat 1minute Determination of the Polarization Index for a winding is built into the Digital Tester. Simply follow the procedures for a Hipot test (refer to DC Hipot Test and Set-Up on page 5-3). When the desired voltage is reached, press the TIME=0 RESET FUNCTION button. Conduct the test for at least ten minutes (600 seconds) by holding the TEST button for that time (the time of the test appears in the upper left corner of the display). The measured insulation resistance at the end of one minute (60 seconds) will appear in the upper center portion of the screen. At the end of ten minutes, the measured Polarization Index (PI) will appear in the upper right corner of the screen. Do not touch test leads while test is in progress! User s Manual 8-1 Rev. C(13)-7/99

89 Additional Tests Store Polarization Index Results 1. Press the function key corresponding to STORE. A list of available Records will appear. The menu bar at the top of the screen also changes. 2. Press the function keys corresponding to UP and/or DOWN to bring the cursor to the desired Record. Press SELECT. 3. Be sure PI is highlighted in the second column. (Press the function keys corresponding to UP and/or DOWN as necessary.) The Polarization Index value will be stored to the Record that was selected in the step above. The main menu will reappear and the next motor may be tested. Polarization Index Evaluation There is no rule of thumb in determining what is a good Polarization Index, but several things can be observed in order to determine pass/fail criteria. Low ratio values can be expected whenever items with short runs of wire are tested, such as small motor windings. In this case, the maximum insulation resistance value can be reached in just a few minutes, indicating a low PI value. If the resistance value increases rapidly in the first few minutes of the test, the winding is probably good. Small rotating motor windings typically have PI values of 1.5 or higher. Older stators, which use paper tape for insulation can have good PI values of 2.5 or higher. Generators with epoxy insulation have PI values of 2.0 or less. Oil-filled transformers normally demonstrate lower values between 1.1 and 1.3. Polarization Index test values above and below what is determined to be normal indicate failure. It is recommended that accurate historical records for the Polarization Index tests be maintained, so that results for specific test pieces can be compared for dramatic change, indicating insulation failure. Step-Voltage Test Another test that can be performed using the Digital Tester is the Step-Voltage test. This test be used to indicate the condition of winding insulation. The best results can be had if historical records are maintained of multiple Step-Voltage tests, beginning with measurements made when the winding is new. Use the same voltage increments and time intervals for all Step-Voltage tests of a particular winding. Baker Instrument Company recommends that you plot out your results on graph paper in order for you to make comparisons of different tests or use Baker Instrument Company s MTA 5.0 software package to store the data. NOTE: It is important for the insulation to be free of moisture and dirt when this test is made. 8-2 User s Manual Do not touch test leads while test is in progress! Rev. C(13)-7/99

90 Additional Tests 1. Determine the number of steps you wish to perform, and the voltages and time increments that suit your needs. For example, if the maximum voltage should be 12,000 volts, you may wish to use six steps of 2000 volts each. The time interval will depend on the capacitance of the test piece and the type of insulation it uses. Choose an interval that lets a noticeable change in resistance readings occur at each step. One minute step intervals are fairly standard for many windings. 2. Perform a Hipot test on the winding. Refer to Section 5: DC Hipot Test of this manual if necessary. 3. Keep the TEST button depressed and record the resistance reading at the first voltage step and time interval. It will be displayed in the lower center portion of the screen. 4. Continue to hold the TEST button depressed and note the resistance readings for each subsequent step or time interval. Record these results in memory if desired. For example, with a 12 kv test piece, using steps of 2000 volts and one minute intervals, note the stabilized resistance readings at 2000 volts at one minute, 4000 volts at two minutes, 6000 volts at three minutes, 8000 volts at four minutes, 10,000 volts at five minutes, and 12,000 volts at six minutes. NOTE: At each step, raise the OUTPUT voltage on the tester in single motions to get the most accurate rise from one test voltage to the next. When plotted on graph paper, the results should resemble a set of ascending steps. Each step should be flat, indicating a steady resistance value. Do not touch test leads while test is in progress! User s Manual 8-3 Rev. C(13)-7/99

91 Additional Tests 8-4 User s Manual Do not touch test leads while test is in progress! Rev. C(13)-7/99

92 Appendix A Typical Winding Faults For initial determination of winding faults, refer to the following figures. These wave patterns are typically seen for three phase, wye-connected, lap-wound induction stators. They provide a reference for associating a characteristic wave pattern with a fault-type. NOTE: Variation from these wave patterns is to be expected. Do not consider these wave patterns as absolute. Remember, that due to the variety of motor windings and connections that exist, each motor winding will have its own signature wave pattern. Memorization or exact matches to the following wave patterns is NOT necessary when testing. STORE RECALL PRINT CLEAR Peak: 1500 V Pulse: V/div SURGE 2 us/div Good coil STORE RECALL PRINT CLEAR Peak: 1500 V Pulse: 6 STORE RECALL PRINT RECALL Record 1 Lead V/div 2 us/div CLEAR Peak: 1500 V Pulse: V/div SURGE 2 us/div Shorted single winding 500 V/div SURGE 2 us/div Short partial ground Do not touch test leads while test is in progress! User s Manual A-1 Rev. C(4)-7/99

93 Typical Winding Faults STORE RECALL PRINT RECALL Record 1 Lead V/div 2 us/div CLEAR Peak: 1500 V Pulse: 6 STORE RECALL PRINT RECALL Record 1 Lead V/div 2 us/div CLEAR Peak: 1500 V Pulse: V/div SURGE 2 us/div Solid ground coil 500 V/div SURGE 2 us/div Solid turn-to-turn short STORE RECALL PRINT RECALL Record 1 Lead V/div 2 us/div CLEAR Peak: 1500 V Pulse: 6 STORE RECALL PRINT RECALL Record 1 Lead V/div 2 us/div CLEAR Peak: 1500 V Pulse: V/div SURGE 2 us/div Coil-to-coil short 500 V/div SURGE 2 us/div Phase-to-phase short NOTE: If all three wave pattern comparisons during surge testing show considerable separation when testing three phase windings, the motor has a PHASE-TO-PHASE short. Because two phases are faulty, a good wave pattern will not be achieved in any position of the TLS. STORE RECALL PRINT RECALL Record 1 Lead V/div 2 us/div CLEAR Peak: 1500 V Pulse: 6 STORE RECALL PRINT RECALL Record 1 Lead V/div 2 us/div CLEAR Peak: 1500 V Pulse: V/div SURGE 2 us/div Group-to-group short 500 V/div SURGE 2 us/div Reversed coil A-2 User s Manual Do not touch test leads while test is in progress! Rev. C(4)-7/99

94 Appendix B Troubleshooting PLEASE REVIEW THIS SECTION BEFORE YOU CALL BAKERINSTRUMENT COMPANY OR RETURN THE UNIT Self Help and Diagnostics Problems in testing often crop up. If you are experiencing a problem and believe the problem might be within the Baker Instrument Company Digital Tester, PLEASE take the following steps before calling or simply returning the unit. By performing these procedures and having the requested information available, Baker Instrument Company s Service or Applications Departments will be able to better analyze your situation and provide the appropriate response. Either department may be reached at (970) or toll-free at STEP #1: Basic Information Take down all basic instrument information, include the following: Model # example: D12000 Serial # example: D951 Product # example: NOTE: All information above is located on the rear panel product label. If the tester has special options installed that you are aware of, please note these. Any and all information you know or can derive would be of help! A great tool would be a printout or sketch of the waveforms displayed on the tester. STEP #2: Applications or Service Problem? Generally speaking, if a problem is noted ONLY when testing a specific motor/ generator or other coil type, then APPLICATIONS would be involved. See Applications: What to Do First! on page B-2. Please call Baker Instrument Company, Sales Department for APPLICATIONS assistance. If you can NOT say the problem is associated with any ONE type of motor/ generator, then SERVICE would be involved. See Service: What to Do First! on page B-4. Do not touch test leads while test is in progress! User s Manual B-1 Rev. C(4)-7/99

95 Troubleshooting Applications: What to Do First! Review the section below on Common Application Problems. Please have Basic Information about your tester and specific information about the motor you are testing available when calling or faxing to assist Baker Instrument Company personnel in determining a solution to your problem. NOTE: Hp rating; kw rating; RPM rating; Operating voltage & current; How the item being tested is wound and/or number and type of coils; Application of motor/generator. In short, any and all information you know or can derive from the motor name plate would be of help! A great tool would be a printout or sketch of the waveforms displayed on the tester. If you have a FAX available, send a draft to , Attn.: Applications. Common Application Problems There are a few common application-related problems which many users encounter. Please review the following cases. A. The surge tester will not give the desired output test voltage for the apparatus under test. This is often the case when the motor under test is too large for the instrument being used, or if the impedance of the windings is too low. Refer to Section 6 Surge Testing for specific test procedures and results. There may also be a problem with the tester in this case. DO NOT continue testing until you have contacted Baker Instrument Company APPLICATIONS Department. B. Separation of compared wave patterns is seen when surge testing on coils that are assumed to be good, even on brand new motors or windings. Often separation is seen in all three possible comparisons but to varying degrees. There may not be separation throughout the whole wave pattern. This situation can be seen in DC fields or rotating poles. Be sure the coils being compared are being tested in identical configurations; i.e. both coils are wound clockwise beginning to end. On very large equipment, slight differences in capacitance to ground may be the cause. At low voltage levels, begin the test again with the black GRD lead B-2 User s Manual Do not touch test leads while test is in progress! Rev. C(4)-7/99

96 Troubleshooting removed from the motor frame. If the separation is now gone, capacitance to ground was affecting the test. If the above situations do not apply there is probably an imbalance of the impedance in the windings that is inherent to the design. The most common case is found in basket or concentric wound motors. The phases are not magnetically balanced due to different coil lengths. C. There is no damped sinusoidal wave pattern on the display when testing a coil. The wave pattern rises on the left and then slowly drops as it trails off to the right. It may or may not cross the zero/base line. The pattern looks like that in the figure on the next page. The coil under test probably has TOO HIGH an impedance to get a good working pattern. The coil may be very high in resistance and turns count. The inability to surge test this coil, or group of coils in series, will remain unless they can be broken down to smaller units of lower impedance. You may also have a broken test lead or lead to the winding under test. With heavy use, test leads should be checked weekly to ensure there is no breakage. Test leads are easily checked for breakage by firmly grasping the boot and clip in one hand while pulling on the lead with the other. A broken lead will stretch. A good lead will not stretch. Do not touch test leads while test is in progress! User s Manual B-3 Rev. C(4)-7/99

97 Troubleshooting Service: What to Do First! STOP! Do not aggravate any possible problem by INCREASING OUTPUT TO MAXIMUM looking for a screen display! Printer Check Because history has shown that several simple solutions which DO NOT require return of unit may arise, PLEASE perform the following checks. The printer does not work when PRINT is selected. The Digital tester will only output to an Epson FX compatible dot matrix printer connected to the tester. Refer to the manual that came with your printer for the DIP switch settings that make the printer Epson FX compatible. Open Condition Display Hipot Display Checks Note the figure below. Is the display you are seeing like this? If yes, the unit may have at least one STORE RECALL PRINT CLEAR RECALL Record 1 Lead 2 broken test lead causing an OPEN 500 V/div 2 us/div condition. The test lead that corresponds to the TLS position that produces this Pulse: 8 type of wave pattern is the lead which is broken. Verify this by pulling on the boot/ clip assembly of the lead. A broken test lead will stretch. If it doesn t, repeat this procedure at one foot intervals for the length of the lead. If the leads of the tester are good, check the connections and continuity of the winding under test. The HIPOT display shows only the VOLTAGE or CURRENT BAR. One of three problems might exist. The item under test is in fact faulty and has either low insulation resistance or open connections. The tester has an internal problem. Peak: 1500 V 500 V/div SURGE 2 us/div The tester has a test lead problem as shown above for an Open Condition. Disconnect the test leads from the motor and isolate the tester from any grounded surface. Reduce the OUTPUT to MIN and attempt a Hipot test under an open lead condition. Your display should indicate a rising voltage bar. The current bar may B-4 User s Manual Do not touch test leads while test is in progress! Rev. C(4)-7/99

98 Troubleshooting Hipot Trip Check Open Ground Check rise slightly but fall back to zero when the output increase is stopped. Do not exceed 10% rotation of output control! There is no need to perform this test at high voltage. If your display still shows NO voltage bar call Baker Instrument Company s Service Department. Use a meter to confirm the insulation resistance of the device being tested. Current bar operation can be tested by shorting test lead #1 and the ground lead together. Under this condition, the voltage bar will NOT move off the zero line and the current bar should rise VERY RAPIDLY and activate the Hipot Overcurrent Trip warning light (HIPOT TRIP). If the HIPOT TRIP light is not activated, check for open test leads at either test lead #1 or the ground lead (see Open Condition Display on page B-4). If the problem persists, contact Baker Instrument Company s Service Department. The HIPOT TRIP lamp either does not activate (under known shorted conditions) or it will not go out when test is discontinued. Call the Service Department immediately for assistance. PLEASE record information off the unit and the specific problem prior to calling. The OPEN GND lamp is on and you are not able to test. Answer these questions: 1. Have you recently moved the unit to new location with possibly an ungrounded outlet? 2. Is the unit being operated in a field where the AC power source is unknown? 3. Is the unit being operated on a scope cart that has its own outlet or power source? 4. Is the unit being operated using a two-wire extension cord? 5. Is the unit being operated on a transformer isolated circuit? If your answer is yes to any of these questions, the unit is probably operational and indicating you have an open AC line ground connection. In the case of numbers 1 through 3 above, use an outlet tester to assure proper wiring connections to the outlet. For number 4, replace the two-wire extension cord with a two-wire/with ground extension cord. In the case of number 5, call Baker Instrument Company Service for assistance.there is an override available but precautions should be taken. Do not touch test leads while test is in progress! User s Manual B-5 Rev. C(4)-7/99

99 Troubleshooting Limited Output Surge Waveform The display shows a limited output (amplitude) surge waveform. The display rises normally but stops at some point. Alternatively, you must continually increase the output control for successive tests to achieve the same output test amplitude. Call the Service Department immediately for assistance on this or any other ABNORMAL CONDITION noted. PLEASE record information off the unit and the specific problem prior to calling. Precautions for Proper Operation NEVER raise the output control to attain a display from a blank screen! NEVER attempt simulated problems by disconnecting the leads and positioning them to ARC against each other! NEVER come in contact with the item under test and the test leads or with the test unit and the item under test! NEVER attempt a two-party operation. Always know what test is being performed and WHEN! NEVER attempt a Burn Out of a detected fault with the tester! Service and Repair A Service Manual for this tester is available from Baker Instrument Company. Ifyou would like to order a copy, please have the model, part, and serial numbers of your tester available when you contact Baker Instrument Company s Service Department. Request part number SMD12. Please allow 3-4 weeks for delivery. Warranty Return Please review the Warranty Notes on page iii and Shipment on page v before sending your tester to Baker Instrument Company for Warranty repair. The Warranty Return Form on the following page MUST BE FILLED OUT and RETURNED with the tester to obtain warranty service. This form will help to ensure that Baker Instrument Company will identify your problem, quickly repair your unit, and return it to you. Authorized Service Centers Baker Instrument Company has several authorized service centers for surge tester repair. Please contact Baker s Service Department at or (970) to find out if your unit can be sent to one of these. B-6 User s Manual Do not touch test leads while test is in progress! Rev. C(4)-7/99

100 Troubleshooting WARRANTY RETURN FORM Please fill out all the following information and return this form with your tester. Make a copy for your records before sending this to Baker Instrument Company. NOTE: Be sure to follow the guidelines in Shipment on page v when sending your tester to Baker Instrument Company. Company Name: Your Name: Mailing Address: Shipping Address: Phone Number: FROM THE NAME PLATE ON THE BACK OF THE TESTER: Baker Product Number: Model Number: Serial Number: DESCRIPTION OF THE PROBLEM: Please give as much information as possible (what is not working, when it happened, what was being tested, any unusual noises, etc.), even if you already talked to someone at Baker Instrument Company by phone. Use the back of this form if necessary. PERSON CONTACTED AT BAKER: SHIP THE TESTER TO: Baker Instrument Company 4812 McMurry Ave., Suite 100 Fort Collins, CO ATTN: Service Manager Do not touch test leads while test is in progress! User s Manual B-7 Rev. C(4)-7/99

101 Troubleshooting B-8 User s Manual Do not touch test leads while test is in progress! Rev. C(4)-7/99

102 Appendix C Calibration This procedure has been simplified for periodic calibration requirements of some of our end users. Calibration may be performed as required and should especially be done in the event any major assemblies or components have been replaced. NOTE: Technicians should be aware that NO major errors should be encountered, unless replacement of major assemblies or components have been made. Introduction Surge calibration is performed using Silver Mica capacitors, which are highly stable components. A periodic check should be all that is required. A full calibration check should be performed once a year. If the check shows major amplitude errors, contact Baker Instrument Company for assistance. An extender card, stock number , is required to do extended re-calibration or service work. Consult Baker Instrument Company s service department for current stock and pricing. Hipot calibration can be performed without use of the extender card as detailed in Hipot Calibration Procedure on page C-4. CAUTION You will be working with high voltage. Take all appropriate steps to safe guard against shock, including use of high voltage gloves if required! Do not touch test leads while test is in progress! User s Manual C-1 Rev. C(11)-7/99

103 Calibration Surge Calibration Procedure Equipment Required Oscilloscope: High Voltage Probe: Digital multimeter High voltage meter probe Inductive load: mhz type 1000:1 Tektronix P6015 or equivalent Single 1 to 5 milli-henries NOTE: An inductive load can be made out of a coil of Romex house wiring. Actual inductance is not critical unless it is at or below 24 micro-henries. Set-Up NOTE: Always set the output by the test scope and check the tester display against the test scope! This is a quick check procedure. At no point should attempts be made to re-calibrate individual volts/division settings until the total check is complete! 1. Using the diagram below, connect the tester to the inductive load and connect the test oscilloscope as shown. 2. Preset the tester unit controls as follows: a. FUNCTION switch to SURGE. b. Set the TEST Lead SELECT (TLS) switch to #1. c. VOLTS/DIV switch to 500 Volts/division. d. OUTPUT control to minimum. NOTE: Always set the output voltage by the test scope and check the tester display against the test scope. C-2 User s Manual Do not touch test leads while test is in progress! Rev. C(11)-7/99

104 Calibration 3. Preset Test Scope controls as follows: a. Time base:10 to 20 microseconds b. V/D:1 Volts/division (using 1000:1 Probe) c. Trigger:Negative, internal 4. Initiate testing by depressing the TEST button on the tester and raising the OUTPUT control to give a surge waveform on the screen. Align the wave pattern on the first or second horizontal division below center. NOTE: At this point, it is suggested that CRT controls be adjusted to give the best display possible. Make adjustments using INTENSITY and SECONDS/DIV as the primary controls. 5. Monitor the test scope for a wave pattern, going negative. Adjust the tester OUTPUT control for a two division wave pattern on the test scope, or 2000 V. NOTE: Measurements are ALWAYS taken from the baseline to first peak, either negative for the test scope, or positive for surge tests. 6. Check the surge test display against the test scope. The amplitude error percentage should not exceed 5% for full scale readings. 7. Repeat Step 6 for all other VOLTS/DIV settings, raising the tester s OUTPUT control as required. It is suggested that the output be at least twice the Volts/division setting. For example, for a Volts/division setting of 1000 V, the output should be 2000 V. Use higher outputs when possible, but DO NOT increase the output to a point that the wave pattern on the display goes off the screen! Do not touch test leads while test is in progress! User s Manual C-3 Rev. C(11)-7/99

105 Calibration Hipot Calibration Procedure Equipment Required Set-Up Oscilloscope: High Voltage Probe: Digital multimeter High voltage meter probe Resistive load: mhz type 1000:1 Tektronix P6015 or equivalent 10 mega-ohm, 20 watt minimum NOTE: These instructions assume the technician is using a 10 mega-ohm, 20 watt minimum resistive load. 1. Disconnect the surge inductive load, if any. Use test leads #1 and the black ground lead to connect the resistive load across the leads. 2. Connect a digital meter high-voltage probe across the load and observe polarity. 3. Preset the tester unit controls as follows: d. FUNCTION switch to HIPOT 100 µ-amps/div. e. Set the TEST Lead SELECT (TLS) switch to #1. f. VOLTS/DIV switch to 500 Volts/division. g. OUTPUT control to minimum. 4. Depress the TEST and raise the OUTPUT to indicate 2000 V on the test meter. NOTE: The TLS has NO effect on the Surge Tester function or test mode. The FUNCTION switch performs the required change to Hipot test mode. 5. Verify on the display that the Hipot Voltage Bar (left side of screen) indicates avoltage equal to that on the meter, +/- 5%. It should be four divisions or 2000 V. 6. After verification, discontinue testing and disconnect the meter probe. 7. Re-establish a test at 2000 V and check the Hipot Current Bar (right side of screen) and the Hipot digital current reading from the lower right corner of the display. The current should be 200 micro-amps +/- 5%. NOTE: The formula I = E/R is in effect. Therefore, adjust the current reading for the exact resistance used if it is other than 10 mega-ohms. 8. When the current reading is verified, decrease the current micro-amps (FUNCTION switch) to the next lowest µ-amp/div value and check for a C-4 User s Manual Do not touch test leads while test is in progress! Rev. C(11)-7/99

106 Calibration Special Hipot Notes Hipot Adjustments HIPOT TRIP. If a trip does not occur, drop to the lowest current setting and check for a trip. If a trip still does not occur, contact Baker Instrument Company s Service Department for assistance. 9. Discontinue the test and remove the resistive load. Isolate test lead #1 from ground or any other grounding source (such as a concrete floor). 10. Reset the tester s VOLTS/DIV switch to the lowest setting and the current µ- AMP/DIV setting (FUNCTION switch) to the highest setting. Raise the OUTPUT to 2000 Volts. Verify that the tester reading is +/- 5% of the meter reading. Power supply adjustments will affect Hipot readings. Often a simple trimpot correction is enough to bring Hipot calibration into specification. However, Hipot top-end voltage often exceeds (slightly) the rated output of the tester, but rarely by more than 10-20%. If you have made the calibration correction during the checkout above and find an excessively high top end Hipot reading, expect a stack problem, primarily shorted SCRs. The stack assembly should be accessible and is located directly behind the card cage. It is the top most board and has either 3 or 5 dual packaged SCR modules on it. Using an ohmmeter, check resistance of all 1 mega-ohm resistors between SCR modules. Resistance should be in the 800K to 1 mega-ohm range, with shorted SCRs indicating a very low resistance reading. If SCRs are found shorted, contact Baker Instrument Company s Service Department for current pricing and availability. Once replacement is complete, return to start of Hipot calibration and recheck, making adjustments as required. NOTE: Shorted SCRs do not affect surge calibration. Only the top-end voltage is affected. Hipot adjustment trimpots are accessed when the I/O Board (80-108) is on an extender board. The I/O Board is located in the card cage, and has the FUNCTION select switch on the front panel. It is the board on the right side of the cage. There are two trimpots for the Hipot test. Adjustment of R22 will affect both the Hipot Current Bar and the digital Hipot current reading. Adjustment of R21 will affect both the Hipot Voltage Bar and the digital Hipot voltage reading. Do not touch test leads while test is in progress! User s Manual C-5 Rev. C(11)-7/99

107 Calibration C-6 User s Manual Do not touch test leads while test is in progress! Rev. C(11)-7/99

108 Appendix D PP130/PP230 Power Pack The use of the PP130/PP230 Power Pack incorporates a system of two separate units; a 12 kv host unit (the Digital Tester) and a 30 kv power pack. The 12kV portion of the system is capable of stand alone operation for Surge or DC Hipot test functions. The power pack relies on the 12 kv host unit to provide triggering and readout functions and cannot operate alone. Instructions for stand alone operation of the 12 kv host unit should be reviewed in the main portion of this manual before attempting operation with the 30 kv power pack. This supplemental manual will provide instruction on how to correctly set up, connect, and operate the power pack, and other important safety information. CAUTION NEVER ATTEMPT TESTING A LOAD WITH BOTH 12 kv AND POWER PACK TEST LEADS ATTACHED TO THE LOAD AT THE SAME TIME! NOTE: The ground fault system on the 12 kv host tester will render it inoperative without a proper ground. When the host tester is connected to the PP130/230, any inoperable condition will also affect the power pack due to loss of the surge enable signal. THESE INSTRUMENTS SHOULD NEVER BE USED WITHOUT A GROUNDED SUPPLY. Caution Notes User safety demands that the tester output NEVER be activated without connection to a winding load of some type. Please refer to the host tester instructions in the main portion of this manual for connection procedures to various windings. REMEMBER: The host tester s VOLTS/DIV switch affects only the display amplitude on the CRT. It does not control or limit the output voltage of the host unit or power pack in any way. Do not touch test leads while test is in progress! User s Manual D-1 Rev. C(12)-7/99

109 PP130/PP230 Power Pack Emergency Shut-Off Button The 30 kv power pack is equipped with a large, red EMERGENCY SHUT-OFF button on the front panel of the unit. It is located to the right of the TEST button. Use it to quickly discontinue a test and to shut off all power to both the power pack and the Digital tester. The emergency shut-off button is a two position switch. While in the in position, power is supplied to both the power pack and the Digital tester and testing can proceed as normal. When is put into the out position by pressing it once, any test that is in progress will immediately stop and the power to both units will turn off. To resume testing with the power pack and/or the Digital tester, depress the emergency shut-off button again (it must be in the in position). The ON/OFF switch lights of both units will turn on. Follow the procedure for Power Pack Operation on page D-3 to continue. Initial Set-Up These instructions refer to the PP VAC Power Pack. Instructions are identical for the PP VAC power pack. 1. Connect the power pack to the tester. Us the short AC line cord on the power pack front panel to connect to the 12 kv host tester power entry receptacle (LINE IN). 2. Connect the 25-pin interconnect cable between the front of the two units. The cable is marked on each end. Be sure to plug in the end marked HOST into the Auxiliary port (AUX) on the front of the Digital Tester panel and the end marked 30KV into the Auxiliary port (AUX) on the front of the Power Pack. 3. Connect the long AC power cord to the power pack front panel receptacle and then to an appropriate AC power source. For 220/240 Volt power packs, please see Note Regarding 220/240 VAC Units on page D-6 concerning AC line cord connectors. Both units are now ready for operation. The host tester is equipped with a ground fault monitor and indicator. This circuitry should not hinder operation on GFI protected AC power circuits. If you find that a problem exists, the internal ground monitoring circuit may be disabled. Please call Baker Instrument Company s Service Department at for assistance. The ground fault monitor must also be disabled in the event that the unit is to be operated on a transformer isolated AC circuit. Failure to do so will cause a loss of ground indication, disabling the high voltage power section of the unit. Please assure safe operating practices whenever disabling the ground monitor circuit! It is advised that some type of external grounding strap be used. D-2 User s Manual Do not touch test leads while test is in progress! Rev. C(12)-7/99

110 PP130/PP230 Power Pack Power Pack Operation Surge Testing 1. Power-up the 30 kv power pack and host tester. Follow the host tester set-up procedures in this manual (refer to Single Coil Surge Test and Set-Up on page 6-3 or Three Phase Motor Surge Test and Set-Up on page 6-6). NOTE: The PP130/230 requires a one to two minute warm up prior to operation. 2. Set the 12 kv host tester FUNCTION control switch to the AUX (auxiliary) position. NOTE: The volts per division settings when the AUX is selected will change the Volts/divsion settings from 500, 1000, 2000, and 3000 Volts/div to 1250, 2500, 5000, and 7500 Volts/div. The 1250 Volts/div setting is not available with the PP130/PP230 and an error message will appear on the display when this setting is selected. Use 2500, 5000, and 7500 Volts/div only. 3. Assure the power pack OUTPUT control is at MIN, (full counter-clockwise). 4. Connect the power pack leads to the appropriate load. See Lead Connections on page D-6 for proper test lead connection. NOTE: It is important to connect the safety ground (the smaller diameter black ground lead) to the frame of the test winding and NOT to the coil ground lead. Results of the surge test will be erroneous if the coil ground lead is used instead of the frame for grounding. CAUTION HIGH VOLTAGE ACTIVATION IS NEXT. ENSURE THAT ALL PERSONNEL ARE AWAY FROM THE DEVICE UNDER TEST AND ARE NOT IN CONTACT WITH EITHER THE LOAD OR TEST LEADS! WARNING! SOME TEST LEADS WILL BE OPEN DURING THE TEST AND CAN BE AT THE SAME VOLTAGE POTENTIAL AS THE WINDING! ALL PRECAUTIONS SHOULD BE MADE TO AVOID TOUCHING THESE LEADS. Do not touch test leads while test is in progress! User s Manual D-3 Rev. C(12)-7/99

111 PP130/PP230 Power Pack DC Hipot Testing 5. Start test by depressing the power pack TEST switch (or FOOTSWITCH) and slowly raise the power pack OUTPUT control. A pattern should immediately be visible on the display screen of the host tester. If not, recheck the connections and all the switch settings. Also assure that the interconnect cables have been attached and are secure. 6. The display may require adjustment for optimum clarity, sweep and positioning. Make any adjustments required prior to continuing the test. 7. Determine your test voltages and adjust the VOLTS/DIV setting so that the waveform is fully displayed without going off the screen. 8. When the test is completed, release the TEST switch of the power pack and return the OUTPUT control to its minimum setting. 9. Store the wave pattern into the internal memory of the host unit, or onto a computer connected to it. See Section 3: Storage and Print Capabilities. 10. Reposition the red (HOT) and the black (GROUND) test lead, previously connected to the leads of the windings. Refer to Lead Connections on page D-6. Compare all phases against each other: #1 vs. #2, #2 vs. #3, and #3 vs. #1. By switching one hot and the ground lead each time, the operator can make all the measurements necessary for these comparisons. The operator may find it advisable to mark or identify the stator leads at the time of, or prior to the first test. 1. Power-up the 30 kv power pack and host unit. Follow host tester set-up procedures in this manual (refer to DC Hipot Test and Set-Up on page 5-3). 2. a. Set the host unit s FUNCTION switch to the AUX setting. b. Set the 30 kv Power Pack s FUNCTION switch to the HIPOT setting. NOTE: As the Power Pack s FUNCTION switch is changed to the HIPOT setting, a loud relay noise will be heard. This is normal for the Power Pack. 3. Connect the red (HOT) lead from the power pack to the windings to be tested, and the black GROUND leads to the iron or core material. 4. Begin testing by depressing the power pack TEST switch and slowly increasing the OUTPUT control. As the OUTPUT is increased, the Voltage Bar rises up slowly and the Current Bar rises rapidly on the right side showing the charging current. When the OUTPUT is held at a given voltage setting, the Current Bar will fall and remain at a constant level to indicate the leakage current. D-4 User s Manual Do not touch test leads while test is in progress! Rev. C(12)-7/99

112 PP130/PP230 Power Pack NOTE: This test should be interrupted any time a fast, sharp rise in the current is observed. NOTE: The over-current Hipot trip levels that activate the HIPOT TRIP light are ten times the micro-amps/division settings on the tester. The trip levels are 10, 100, and 1000 micro-amps. Releasing the TEST button will reset the over-current trip to begin testing again. 5. Adjust VOLTS/DIV and µ-amps/div to best monitor the voltage and current levels. Note the voltage, resistance in mega-ohms, and leakage current levels displayed on the screen. 6. When the desired test voltage has been achieved, press the TIME=0 FUNCTION button (the right-most button above the CRT display). The elapsed time displayed in the upper left corner of the screen will reset to zero. NOTE: Use TIME=0 function to be sure the full DC voltage potential is applied for the required test time. In this way, the time required for voltage rampup will be discounted for both Hipot and Polarization Index tests. NOTE: If MTA software is being used with a personal computer, transfer the data to the computer prior to releasing the TEST button. 7. Upon completion of the test, return the OUTPUT control to MIN and release the TEST button. If desired, store the hipot data into the internal memory of the host unit. See Section 3: Storage and Print Capabilities. NOTE: Always allow a sufficient time for the winding under test to completely discharge before disconnecting the test leads. The recommended practice is to discharge the winding for a duration of at least five times the duration of the DC Hipot test for high voltage windings. CAUTION Disconnect the unit s test leads not being used from the load. NEVER USE THE HOST UNIT S GROUND LEADS FOR GROUNDING DURING THE 30 kv POWER PACK TEST! NOTE: For Hipot operation of the 12 kv host tester alone, the host tester and the power pack must be disconnected from each other. For Surge operation of the 12 kv host tester alone, the operator need not disconnect the two units. Simply place the 12 kv host unit FUNCTION switch back to the SURGE position. The host unit is now ready to Surge test alone. Do not touch test leads while test is in progress! User s Manual D-5 Rev. C(12)-7/99

113 PP130/PP230 Power Pack Lead Connections RED = hot lead BLK/BLU = larger diameter black grounded lead with blue braided cover SM BLK = smaller diameter black grounded lead NOTE: It is important to connect the safety ground (the smaller diameter black ground lead) to the frame of the test winding and NOT to the coil ground lead. Results of the surge test will be erroneous if the coil ground lead is used instead of the frame for grounding. NOTE: Some test leads will be open during the test and can be at the same voltage potential as the winding! All precautions should be made to avoid touching these leads. Three Phase Motor: Wye Connected Motor Leads Lead 1 Lead 2 Lead 3 FRAME Test Phase 1 RED BLK/BLU OPEN SM BLK Test Phase 2 OPEN RED BLK/BLU SM BLK Test Phase 3 BLK/BLU OPEN RED SM BLK Three Phase Motor: Delta Connected Motor Leads* Lead 1 Lead 2 Lead 3 FRAME Test Phase A RED BLK/BLU OPEN SM BLK Test Phase B OPEN RED BLK/BLU SM BLK Test Phase C BLK/BLU OPEN RED SM BLK * (Phase A = L1 L2; Phase B = L2 L3; Phase C = L3 L1) Note Regarding 220/240 VAC Units 220/240VAC input units may require the user to supply an appropriate AC connector for mating to the power source. These units are designed for use on asingle (1) phase, 220/240VAC power source. Split phase AC power sources will not work. Color codes for the AC line cord supplied are as follows. Brown Blue: Green/Yellow: AC line HOT AC line NEUTRAL AC line GROUND (earth) D-6 User s Manual Do not touch test leads while test is in progress! Rev. C(12)-7/99

114 Appendix E Model AT101D Bar-to-Bar Armature Test Accessory The Model AT101D Bar-to-Bar Armature Testing Accessory is an adaptor which converts any Baker Instrument Company surge tester with an output of up to 15 kv into a low impedance, high current, bar-to-bar armature tester. The barto-bar test method is recognized as superior to the span test method for testing armatures. To illustrate the difference between the bar-to-bar and span tests, consider this example. A manufacturer of lap wound elevator motor armatures determines that, to thoroughly test the turn-to-turn and coil-to-coil insulation, a test voltage of 400 volts across each coil is required. However, the impedance of a single coil in the armature is so low that it appears as a dead short to a conventional surge tester designed for testing AC stators. Even with the hefty current of a 12 kv surge tester, only a few hundred volts may be generated into such a load. Most of this voltage is actually lost in the test leads of the surge tester. Consequently, the span test was developed (see the figure below). In the span test, the test contacts are placed several bars apart, so that the impedance of several coils in series is large enough to be tested with the surge tester. For example, to generate 400 volts across each coil of a 10 bar span, the test voltage must be increased to 4000 volts. However, 4000 volts at the high voltage contacts delivering the surge test will over-stress and probably damage the ground insulation at the first coil in series. Therefore, the maximum test voltage must be decreased to the same level as the safe DC Hipot voltage for that motor, or about 2000 volts. Now the coils are not adequately being tested, since the bar-to-bar voltage is only 200 volts. In a bar-to-bar surge test, 400 volts is applied directly to each coil without overstressing the ground insulation (see figure below). The AT101D Bar-to-Bar Testing Accessory provides a specially designed low output impedance surge tester with low impedance test leads to make this test possible. Bar-to-Bar Test Span Test Do not touch test leads while test is in progress! User s Manual E-1 Rev. C(11)-7/99