ECET 211 Electrical Machines and Controls

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1 ECET 211 Electrical Machines and Controls 2016/4/27 Class Review and Wrapping Up Comprehensive Exam, Friday, 1:00-3:00 PM, May 6, 2016 Close books/allow 1-page (8 x 11 and ½) hand-written review note, double sided Question types o Multiple choice o Fill-in blanks o Circuit diagram/drawing completion of the unfinished part o Simple calculations Ohm s laws Simple circuit, resistance, current, etc Single phase Three-phase: Power, power factor, Line/phase voltage, line/phase current Transformer: Vp/Vs, Ip/Is, Np/Ns Three-phase Delata, Wye connections Energy, Power, Torques applications Chapter 1. Safety in the Workplace Chapter 2. Understanding Electrical Drawings Part 1. Symbols-Abbreviations-Ladder Diagrams o Motor Symbols o o Motor Terms (abbreviations) Motor Ladder Diagrams Figure 2-1 Motor Control Symbols Figure 2-3 Typical ladder diagram Figure 2-4 Motor power and control circuit wiring Figure 2-5 Identification of coils and associated contacts Figure 2-6 Load and control devices Figure 2-7 Loads and places on the right and contacts on the left Figure 2-8 Stop devices connect in series and start devices connect in parallel Figure 2-8 Differentiating between multiple devices of the same type Figure 2-10 Ladder diagram with run number detailed Figure 2-11 Numerical cross-reference system Figure 2-12 Wire numbering Figure 2-13 Alternative wiring identification with documentation Figure 2-14 Representing mechanical functions (FWD, REV) Figure 2-15 Control transformers ground connection Part 2 Wiring Single Line Block Diagrams o Wiring Diagrams o Single-Line Diagrams o Block Diagrams Part 3. Motor Terminal Connections o Motor Classifications 1

2 o DC Motor Connections Dynamic braking o AC Motor Connections Dual voltage motor connections Multispeed motor connections Motor direction change Part 4. Motor Nameplates and Terminology o NEC Required Nameplate Information Motor Manufacturer, Voltage Rating, Current Rating Line Frequency, Phase Rating, Motor Speed Ambient Temperature, Temperature Rise, Insulation Class Duty Cycle, Horsepower rating Code Letter, Design Letter o Optional Nameplate Information Service Factor, Motor Enclosure, Frame Size, Efficiency, Power Factor Thermal protection, Connection diagrams o Guide to Motor Terminology, p. 38 Across-the-line, lock-rotor current,.. Part 5. Manual and Magnetic Starters 2

3 Chapter 3. Motors, Transformers and Distribution Systems Part 1. Power Distribution o Transmission Systems o Substations Unit Substations High-voltage primary switchgear Transformer sections Low-voltage distribution section o Distribution System Figure 3-6 Typical commercial/industrial distribution system Figure 3-7 Single-line diagram for a typical distribution system o Power Losses o Switchboards and Panelboards Figure /480V three-phase four-wire Figure 3-12 Panelboard grounding and bonding o Motor Control Centers (MCCs) Part 2. Transformer Principles o Transformer Operation o Transformer Voltage, Current, and Turn Ratio Figure 3-20 Step-up transformer Figure 3-21 Step-down transformer Figure 3-22 Step-won transformer connected to a resistive load o Transformer Power rating Single-phase kva = I * E/1000 Three-phase kva = (1 * E * 1.732)/1000 o Transformer Performance (losses) Core losses (Iron loss) Coil losses (copper loss) Temperature rise Voltage regulation Part 3. Transformer Connections and Systems Transformer Polarity High-side, Low-side Single-phase Transformers Figure 3-27 Control Transformer used in Motor Control Applications Figure 3-28 Typical dual voltage 480 V and 240V transformer connections Figure 3-29 Fuse protection for both the primary and secondary of the transformer and at the ground connection for a ground control system Three-Phase Transformers Figure 3-30 Common transformer connections o Wye-Wye connection o Delta-Delta connection o Delta-Wye connection Figure 3-31 Three-phase, three-wire delta transformer connection supplying power to a three-phase motor load Figure 3-32 Wye connected, three-phase, four-wire distribution system 3

4 Figure 3-33 Typical delta-to-wye, three-phase, four wire transformer configuration Auto Transformer Applications o Variable voltage o Autotransformer motor starter Instrumentation Transformers Current transformer (CT) Potential transformer (PT) 4

5 Chapter 4. Motor Control Devices o Part 1. Manually Operated Switches o Primary and Pilot Control Devices o Toggle Switches o Push Button Switches Figure 4-3 PB symbols and switching action Figure 4-4 Break-make PB and typical motor control circuit Figure 4-14 Emergency stop PB and motor control o Pilot Lights Figure 4-15 Remote start/stop station with run pilot light Figure 4-17 Push-to-test pilot light o Selector Switch Figure 4-18 Three-position selector switch o Drum Switch Figure 4-18 Drum switch used for reversing the direction of rotation of a threephase motor o Part 2. Mechanically Operated Switches o Limit Switches Figure 4-21 Limit switch symbol and configuration Micro-switch (Micro limit switch) o Temperature Control Devices Figure 4-28 Temperature switch utilized as part of a motor control circuit (230V fan motor) Pressure Switches Figure 4-30 Pressure switch used as part of an air compressor control system Float and Flow Switches Figure 4-31 Float switch symbols and circuit (water level control) Figure 4-32 Flow switch symbols and circuit (liquid flow control) o Part 3. Sensors Proximity Sensors Inductive proximity sensors Capacitive proximity sensors Photoelectric Sensors Through-beam scanning Retrorefelctive scanning Diffuse scanning Fiber optics Hall Effect Sensors Current measurement applications Speed measurement Ultrasonic Sensors Temperature Sensors Thermocouple Resistive Temperature Detectors (RTDs) Thermistors (Negative temperature coefficient) IC package 5

6 o Velocity and Position Sensors Tachometer Magnetic pickup Encoder Flow Measurement Turbine flow meters Target flow meters Magnetic Flowmeters Part 4. Actuators Relays Figure 4-63 Electromechanical relay Figure 4-64 Relay motor control circuit Solenoids Figure 4-67 Solenoid construction and operation Solenoid Values Figure 4-69 Solenoid valve energized and deenergized Figure 4-70 Solenoid-operated tank filling and emptying operation Stepper Motors Servo Motors Figure 4-74 Closed-loop servo system Figure 4-75 DC Brushless servo motor 6

7 Chapter 5. Electric Motors Part 1. Motor Principle o Magnetic field and Flux o Induction (voltage/current) and Energy conversion o Applications: Motor, Generator Part 2. Direct Current Motor o Major components of a DC motor o Major Classifications Permanent Magnet DC Motor Series DC Motor Shunt DC Motor Compound DC Motor o Direction of Rotation o Motor Counter Electromotive Force (EMF) and its Effects Example 5-1 DC Motor Ia, and EMF calculation o Speed Regulation Example 5-2 o DC Motor Speed Control Methods o DC Motor Drives Part 3. Three-Phase AC Motors o Speed equation: N = 120*f/P o Induction motor Squirrel-case Induction Motor, p 114 Wound-rotor Induction Motor, p. 118 o Speed-Torque Characteristics and Applications, p. 115 NEMA Design B NEMA Design C NEMA Design D o Motor Slip Example 5-4 o Power Factor o Dual-speed three-phase squirrel-cage single winding motor Part 4. Single-Phase AC Motors o Split-Phase Motor, p. 121 o Split-Phase Capacitor Motor (Capacitor-start), p. 123 o Dual-Speed Capacitor-Start Motors, p.124 o Reversible Permanent-Capacitor Motor, p. 124 o Capacitor-Start/Capacitor-Run Motor, p. 124 o Shaded-Pole Motor, p. 125 o Universal Motor, p. 125 Part 5. AC Motor Drives o Variable-Frequency Drive AC to DC Converter (rectifier) DC filter Inverter (DC to AC conversion) Volt/Hz ratio PWM control o Inverter Duty Motor 7

8 Part 6. Motor Selection o Mechanical Power Rating o Current o Code Letter (NEMA Locked-Rotor Code, kva/hp) o Design Letter o Efficiency o Energy-Efficient Motors o Frame Size o Frequency o Full-load Speed o Load Requirements Constant-torque load Variable-torque load Constant-horsepower load o Motor Temperature Ratings Ambient temperature Temperature rise Hot-spot temperature Insulation class o Duty Cycle Continuous duty Intermittent duty o Torque Lock-rotor torque (LRT) = starting torque Pull-up torque (PUT) Breakdown torque (BDT) = pull-out torque Full-load torque o Motor Enclosure Types o Metric Motors (50 Hz, 60 Hz: speeds) Part 7. Motor Installation o Foundation o Mounting o Motor and Load Alignment Direct-drive motors Coupling by means of Gears or Pulley/Belt Example 5-5 o Motor Bearings o Electrical Connections o Grounding o Conductor Size Example 5-6 o Voltage Levels and Balance o Built-In Thermal Protection Part 8. Motor Maintenance and Trouble Shooting 8

9 o o Motor Maintenance Schedule Periodic Inspections Brush and Commutator Care Testing Winding Insulation Keep Motor Clean Keep Motor Dry Check Lubrication Check for Excessive Heat, Noise, and Vibration Excessive Starting is a Prime Cause of Motor Failures Troubleshooting Motors DMM Voltage measurement, continuity and motor winding resistance Special type DMM includes: Capacitance measurement, frequency and temperature measurement functions Clamp-on ammeter Mega-Ohmmeter Infrared (IR) thermometer Tachometer Oscilloscope 9

10 Chapter 6. Contactors and Motor Starters Part 1. Magnetic Contactor o Switching loads o Heater control circuits: Delta heater load Line current, Line voltage, three-phase power o Definite-purpose contactor Latch coil/unlatch coil Lighting control circuit o Contactor Assembly Shading coil o Arc Suppression Part 2. Contactor Ratings, Enclosures, and Solid-State Types o NEMA Ratings NEMA contactor size guide (Figure 6-22) Example 6-1 Load Utilization Categories Nonlinear loads Resistive loads Inductive loads Capacitive loads o IEC Ratings AC Categories DC Categories o Contactor Enclosures Environmental factors Non-Hazardous location Hazardous Location o Solid-State Contactor Silicon Controlled Rectifier SCR testing circuit Dual SCR for AC load Solid-state contactor digital control Part 3. Motor Starters o Magnetic Motor Starters Manufacturer-installed control wiring Figure 6-31 Magnetic motor starter o Motor Overcurrent Protection Figure 6-33 Magnetic motor starter with separated mounted start-stop pushbutton station Figure 6-34 Major functional blocks for motor operation o Motor Overload Relays o Thermal Overload Relays o Full-load amperage (FLA) of the motor and the motor starter size o Dual-Element Fuses o NEMA and IEC Symbols 10

11 Chapter 7. Relays Part 1. Electromechanical Control Relays o Relay theory of operation o Relay control circuits o Relay applications Using a relay to control a high current load with a low-current transistor circuit Diode, Transistor o Relay styles and specifications Part 2. Solid-State Relays o Solid-state relay operation o Specifications o Switching controls Zero voltage crossing o Three-phase Multiple-pole SSR connections Chapter 8. Motor Control Circuits None 11

12 Chapter 9. Motor Control Electronics Diode o Basic theory o Diode Applications Switch, flying wheel diode Rectifiers: half-wave, full-wave, three-phase full-wave Transistor o Basic theory o Relay control, AC load on/off switching Photo-Transistor o PLC Input Module: Full-wave rectifier, Zener diode (voltage regulator), Optical coupler o PLC Output Module: Optical coupler, Triac IGBT o Basic theory o IGBT used in electric motor control (inverter) Triac o Basic theory o Small AC Load control using Triac (light dimmer, small AC motor) Chapter. 10 Adjustable Variable speed drive Simplified circuit of a PWM inverter Pulse-width Modulation Inverter Motor and Drives 12

ECET 211 Electric Machines & Controls Lecture 4-2 Motor Control Devices: Lecture 4 Motor Control Devices

ECET 211 Electric Machines & Controls Lecture 4-2 Motor Control Devices: Part 3. Sensors, Part 4. Actuators Text Book: Electric Motors and Control Systems, by Frank D. Petruzella, published by McGraw Hill,