TECHNICAL DESCRIPTION Issue 1.00 FOR 4-QUADRANT SERVO AMPLIFIER AS 3HE - EUROCARD FOR DC-MOTORS UP TO 3,4 kw TYPE MTRS 170-xx MATTKE AG Leinenweberstraße 12 D-79108 Freiburg Germany Telefon: +49 (0)761-15 23 4-0 Telefax: +49 (0)761-15 23 4-56 E-Mail: info@mattke.de http://www.mattke.de
for MTRS 170-xx 2 25th March 2005 Dear customer, We always try to guarantee for an optimum of security measures and to inform ourselves about the latest developments in technical research. However, it is necessary that we pass on the following further information to you as the user of our components: The appliances are supply parts meant for processing by industry, trade or other factories specialised in electronics. Safety precaution!! Attention - do not touch! The appliances have unprotected live parts. The voltage may be highly dangerous. We also have to inform you that, for your own security, only an expert should work on the appliances. In order to comply with the safety precautions, open connections must be protected against contact with cases, coverings or anything similar. Even after the appliance had been disconnected, there may still be a dangerous voltage (discharges of the capacitors). Due to an error in handling or unfavourable conditions, the electrolytic capacitors may explode. If you have to work on the open appliance, do protect your body (hands!) and your face! Make sure that there is enough ventilation because of the fire risk in case of overheating.
for MTRS 170-xx 3 25th March 2005 CONTENT Page 1. Technical description... 4 1.1 Table of types... 4 1.2 Technical data... 4 1.3 Block diagram... 7 1.4 Description of functions... 8 1.5 Front view... 12 1.6 Adjustment possibilities, measuring points, displays... 13 2. Connections... 14 2.1 Connector assignment... 14 2.2 Function of the different terminals... 15 2.3 Minimum load inductivity... 17 2.4 Polarity of motor and tacho generator... 18 2.5 Correct EMF wiring... 18 2.6 input test circuit... 18 2.7 Connection proposals... 18 3. Initial operation... 21 3.1 Adjustment of pulsed and effective current limits... 21 3.2 Tacho adjustment... 21 3.3 Offset adjustment... 21 3.4 Total amplification... 22 4. Control optimization by means of the customer print... 23 4.1 Soldering bridges... 23 4.2 Tacho-filter... 24 4.3 Scaling of the tacho... 24 4.4 Frequency response of the speed regulator... 25 5. Options... 25 5.1 Ballast circuit... 25 5.2 Tacho monitoring... 26 5.3 Dynamic brake... 27 6. Drawings... 28 6.1 Plan of components, surface... 28 6.2 Plan of components, bottom side... 29 6.3 Plan of components, ballast circuit... 30 6.4 Dimensions... 31
for MTRS 170-xx 4 25th March 2005 1. TECHNICAL DESCRIPTION 1.1 Table of types Denomination nominal pulsed Minimum load Main Heat current current inductivity fuse dissipation MTRS 170/3 3 A 6 A 7,5 mh 5 A Convection MTRS 170/6 6 A 12 A 3,8 mh 8 A Convection MTRS 170/12 12 A 24 A 1,9 mh 15 A Convection MTRS 170/20 20 A 40 A 0,9 mh 25 A Ext. ventilation 1.2 Technical Data The standard amplifier is delivered with a wide band power supply providing the internally needed auxiliary voltage (± 15 V) out of the intermediate DC voltage. In this mode the operation DC voltage may be reduced to a minimum of 20 V. In case this internal power supply is not installed the auxiliary voltage has to be supplied externally and the operation voltage of the final stage may be reduced to 0 V. A supplementary circuit can be used for the tacho monitoring Voltage supply (internal power supply) 20...170 V DC Voltage supply (external power supply) 0...170 V DC Over voltage threshold 250 V DC Standard voltage supply only DC Auxiliary voltage supply (optional) ±15 V, +120/-90 ma Pulsed current time max. 3 seconds Form factor output current < 1,01 Pulse frequency of the final stage 9 khz Frequency between the motor connections 18 khz Band width of the current regulation (45/) 1 khz Set value differential input ±10 V // 40 kohm Tacho range of the actual value 1,7...85 V Available aux. voltage (internal power supply) ±15 V, 20 ma Capacity of the signal outputs +13 V, 15 ma Construction form Euro card 160 mm, 14TE Connection connector DIN 41612-F48 Mounting position horizontal (19 rack) Maximum ambient temperature +45/C...+55/C (mit Derating) Heat dissipation Convection/ at 20 A ventilation Weight 975 gramme
for MTRS 170-xx 5 25th March 2005 Options: * Front panel * Ballast circuit * Tacho monitoring * Dynamic brake * Current regulation Inputs: Speed set value ±10 V and current set value 0...10 V through differential amplifier with common reference level ; tacho input; final stage release +15...+24 V, intermediate circuit connection, auxiliary voltage supply ±15 V (used as input if no internal auxiliary power supply available, else as output for the set value and release command). Outputs: Ready to operate, dynamic brake, I²t-signal, pulsed current limit valu: all as opencollector-outputs (PNP, high-active = +13,5 V); auxiliary power output ±15 V, 20 ma; motor connection. Internal monitoring: Over current, over voltage, under voltage at ±15 V, heat sink temperature, effective - current, pulsed current, external current set value limit (upon request depending of the direction), minimum activation delay time for the dynamic brake (can be switched off). Adjustment possibilities: All the important functions can be adjusted by 19 mm spindle potentiometers, which are accessible through the front panel The potentiometer for the current offset (P202) is only internally accessible. P1 P2 P3 P4 P201 P202 Effective current Tacho Amplification factor of the speed regulator Pulsed current Offset speed regulator Offset current regulator
for MTRS 170-xx 6 25th March 2005 Customer print: The customer print is a printed circuit board containing all the user depending components and adjustments, e.g. the potentiometers P1...P4 and the frequency determining components for the speed and current regulation, furthermore the tacho filter, components for the current limits and soldering bridges. In case of a replacement of the amplifier the old customer print can be placed on the new one thereby allowing to use all the previous adjustments without modification thus saving time. The speed offset (potentiometer P201) is not part of the customer print as this is produced at the operation amplifiers in the basic unit. Speed and current offsets are already adjusted at the factory. The execution MTRS as current regulator is conceived as a standard unit but is provided with a special customer print whose components adjust the speed regulation to 1 and disable a possible tacho signal. LED signals: red: yellow: green: malfunction (over current, over voltage, excess temperature) I²t limit reached ready to operatet
for MTRS 170-xx 7 25th March 2005 1.3 Block diagram
for MTRS 170-xx 8 25th March 2005 1.4 Description of the function 1.4.1 Power supply The direct power supply to the DC intermediary circuit is conceived from the typical multi-axe concept (power input, see block diagram right upstairs). The voltage reaches the final stage and the internal auxiliary power supply through a fuse in each line. The internal power supply card is vertically soldered on the main card and converts the connected DC (allowed range 20...170 V DC, in a short time 250 V DC) into two regulated voltages of + 15 V used to supply the remaining amplifier electronic. This voltage is furthermore available at the main connector. There additional auxiliary circuits (e.g. set value provision) can be connected. A further possibility consists to omit the auxiliary power supply (optional) and to provide the necessary voltage from a main point. This solution is preferable only in case several motor are regulated in one machine. The external supply has to be connected imperatively in case the option tacho monitoring is desired as this card is fitted instead of the internal power supply card. 1.4.2 Differential pre-amplifier Speed set value and current limit value are fed to a differential amplifier and have the same reference point. This point has to be connected to the zero point of the regulation. This concept avoids earth leakages resulting of the common 0 V potential for all axes (negative pol of the DC intermediary circuit). The supply of a current limit value is only necessary in case the soldering bridges LB1, LB2 (customer print) are closed. 1.4.3 Tacho pre-amplifier The voltage of the tacho generator fitted to the motor is connected to a special very precise pre-amplifier. This circuit increases even very low tacho voltages (from 1.7 V as nominal speed) to a level which can be used by the speed regulator Drift an offset voltage of the pre-amplified signal are not higher than the other components of the speed regulation circuit. A filter eliminates voltage spikes and the possible carrier oscillations from the tacho monitoring. The characteristics and the pre-amplification factor can be adjusted by changing soldered components and potentiometer on the customer print.
for MTRS 170-xx 9 25th March 2005 1.4.4 Speed regulator The speed set value and the scaled tacho voltage are connected with the correct polarity to the input of the speed regulator whose characteristics are defined by the components on the customer print. The AC-gain amplification can be adjusted with a potentiometer, this is sufficient for most applications (regulation time constant remains unchanged). 1.4.5 Current set value limiter The value at the output of the speed regulator is interpreted as current set value. This is the point to adjust all types of current limits. By the means of a voltage depending limiting circuit the currents set value can be reduced symmetrically or asymmetrically down to zero. The peak current limit in each direction is determined by Z-diodes on the customer print. With two soldering bridges on the customer print (not mentioned in the block diagram) it may be determined if the current limit value should be limited externally (one bridge for each direction). Only in case of closed soldering bridges the external setting is valid (in the frame of prefixed peak values of the potentiometer) 1.4.6 Extraction of the actual current value The current of one of the output lines is measured by the means of a special circuit as actual current value (in the bloc diagram shown as current converter) and transferred together with the current set value to the input of the current regulator. As for the speed regulator the amplification factors of the current regulator can be modified on the customer print. In this case the characteristic is simpler as the time constant is fixed by SMDcomponents (1 ms), only the amplification factor (standard value KP = 3) may be modified by changing a wire resistor. 1.4.7 Effective current limit Further to the regulation the actual current value is also used for the effective current limitation. Therefore the signal is squared, i.e. the internal characteristic line follows a parable. The result is connected to a low-pass filter (t = 10 sec.). The voltage at the output of this filter is the rate of the actual effective current with reference to an integration time constant of 10 sec. This value is compared with the peak value (potentiometer P1 on the customer print), in case of nearing a special regulation loop which limits indirectly through the adjustment of the optional pulsed current setting the effective current. In extremis the pulsed current limit is equal to the effective current limit.
for MTRS 170-xx 10 25th March 2005 1.4.8 Pulse width modulation A triangle voltage generator with a frequency of 9 khz generates the cycle for the following pulse width modulator. In accordance with the preferred symmetric modulation (for its low heath and noise emission) the modulator produces for each motor connection a balanced but in opposite direction modulated voltage. 1.4.9 Rise delay time, driver and final stage In the circuit rise delay time the control signal of the final stage is processed in order that, although there is an inevitable disconnecting delay time, there is no overlap of the final stage sections in the intermediate circuit. By using the fast switching IGBT final stage and most modern drivers the additional needed rise delay time of a few microseconds has no influence to the regulation. The auxiliary voltage for the positive final stage drivers is produced by means of a load pumping circuit from the auxiliary voltage supply of + 15 V and allows the fully advanced control of all quadrants. 1.4.10 Protection an monitoring logic A special protection logic monitors permanently all the important operation parameters, especially the altitude of the intermediary voltage, current consumption of the final stage, heat sink temperature, + 15 V power supply and the output of the tacho monitoring (if existing). In case of exceeding/falling below of critical limits the final stage is shut down independent of the release signal. The ready to operate signal is only given in case of a faultless device and is not influenced by the external release. 1.4.11 Control output for the dynamic brake. A special output is provided for the control of a dynamic brake. The circuit contains 2 antiparallel wired thyristor in series with a low impedance power resistor. Without activation the thyristor is charged by the EMF of a turning motor and brakes. Only in case of operation of the amplifier (final stage active) the dynamic brake receives a signal and the thyristor remains inactive. Thus the self safety (e.g. in case of a mains breakdown) is guaranteed. As a consequence of the lock of the thyristor once ignited the absolute standstill of the motor has to be awaited until the re-release of the amplifier, if not the final stage will operate against the brake resistor an destroy it. In case the soldering bridge for the use without brake is open the often troublesome delay will not apply.
for MTRS 170-xx 11 25th March 2005 1.4.12 Tacho monitoring To monitor the tacho the hot end of the tacho line is fed with an AC voltage with a frequency above the transfer range of the amplifier. In case of a correctly connected tacho (no short circuit to earth or interruption) the major part of the oscillation can be captured at the end of the other line and thus be used for monitoring. Unfortunately some tacho tend, due to their construction to the formation of a powerful offset voltage with low stability ( copper oxide rectifier, especially after a long standstill on the surface of the commutator). Need and disturbance of a tacho monitoring should be carefully examined.
for MTRS 170-xx 12 25th March 2005 1.5 Front view
for MTRS 170-xx 13 25th March 2005 1.6 Adjustment possibilities, measuring points, displays P1 (customer print) Effective current limit, range 0...100% - of the amplifier specific nominal current P2 (customer print): Tacho; adjustment of the nominal speed P3 (customer print): AC-Gain; adjustment of the AC amplification of the speed control P4 (customer print): I-peak; limit pulsed current, range 10...100% of the amplifier specific pulsed current. P201 (basic unit): Speed-Offset; standstill of the axe at set value 0 V. P202 (basic unit): Current-Offset; output current zero at current set value zero TP 1: I-actual; armature current actual value; 10 V correspond to the device specific pulsed current. TP2: Tacho; tacho original voltage directly generated by the tacho generator. TP3: I-input; pulsed current limit as fed to the differential input. TP4: TP5: TP6: TP7: H201 (red): H202 (yellow): H203 (green): Ua; correcting variable at the current regulator output, corresponds to the medium output voltage of the amplifier. I-set; correcting variable at the speed regulator output after current limitation. n-set; speed set value as fed to the differential input AGND; reference potential for all above mentioned test points, an oscilloscope connected here must be potential free (not earthed) malfunction; lights in case of excess voltage, over current, excess temperature, final stage or tacho failure, final stage switches off. Back in operation by cutting off the auxiliary voltage supply. In case an internal auxiliary power supply is used, the mains must be switched off until the red LED stops lighting. I²t- signal; lights in case the effective current limiter stage is Activated, stops automatically when the load is reduced. Ready to operate, lights synchronously to the ready for use signal at the connector (also without release)
for MTRS 170-xx 14 25th March 2005 2. CONNECTOR 2.1 Pin assignment All the units are delivered with a 48-pin connector according to DIN 41612-F48. In case of considerable orders the amplifiers up to 12 A can be delivered with the more economic 32-pol connector in structural shape D, the layout of the card can be used for both variations. Depending on the connector type the assignment is as follows.
for MTRS 170-xx 15 25th March 2005 Function D32 F48 Tacho (-) 2a 2z AGND --- 2b Tacho (+) 2c 2d +15 V in-/output) 4a 4z AGND --- 4b -15 V (in-/output) 4c 4d AGND 6a 6z AGND --- 6b dyn. brake (output) 6c 6d Current limit reached (output) 8a 8z AGND --- 8b Ready to operate (output) 8c 8d AGND 10a 10z AGND --- 10b reference n-set, I-limit 10c 10d Current limit value (input) 12a 12z AGND --- 12b Speed set value (input) 12c 12d +15 V (output) 14a 14z AGND --- 14b Release (input) 14c 14d Ia-monitor (output) 16a 16z AGND --- 16b I²t-signal (output) 16c 16d Motor, negative (output) 18a,c 18z,b,d Motor, negative (output) 20a,c 20z,b,d Intermediate circuit (+Ucc, input) 22a,c 22 z,b,.d Intermediate circuit (+Ucc, input) 24a,c 24z,b,d Line earth (PGND, input) 26a,c 26 z,b,.d Line earth (PGND, input) 28a,c 28z,b,d Motor, positive (output) 30a,c, 30z,b,d Motor, positive (output) 32a,c 32z,b,d 2.2 Function of the different connections. Tacho input (2d, 2z), [2a, 2c] Input for the connection of a DC-voltage tacho generator for the control of the speed. At the desired speed the tacho voltage must be in the range from 1.7 to 85 V.
for MTRS 170-xx 16 25th March 2005 Auxiliary voltage ±15V (4z, 4b, 4d), [4a, 6a, 4c] On these connections the auxiliary current circuits ±15 V (power supply of the control electronics) are available for external purposes (e.g. encoder) in case an internal power supply is installed. If not these connections are used to fed the amplifier with ±15V DC from an external power supply. The reference point is AGND (electronic-0 V). AGND is connected galvanically to PGND (line earth) inside the amplifier. Dynamic brake (6d), [6c] This output is foreseen to control the optional card dynamic brake. With normal operation there are +13 V on this pin, if the final stage is switched off (for no release, internal failure or switched off power supply) the output has high impedance. In case of the use of a dynamic brake the soldering bridge LB4 must be closed for the release delay. Current limit reached (8z), [8a] In case the pulsed current limiter is active due to a extremely low external limit value this output provides a voltage of +13 V. If inactive the output is impedance high BTB, Ready to operate (8d), [8c] In case the amplifier is ready to operate the pin provides + 13 V DC. The function is independent of the release input. If inactive the output is impedance high. Speed set value (12d, 10d), [12c, 10c] Input to the differential amplifier for the speed set value. The maximum voltage difference may be ±10 V. Although the input is conceived a differential input excessive common-mode interferences must be avoided as the common-mode rejection is only 40 db (remaining part 1%) and overdrive can not be excluded. The difference structure is only useful to avoid mass loops in the input circuit. The connector (10d) [10c] is reference point for the speed set value and also for the pulsed current limit value and should be connected to the ground of the superordinate control (SPS, NC,...). As the reference point is in common the direction can not be inversed by changing the speed set value lines. Pulsed current limit value (12z, 10d), [12a, 10c] Input to the differential amplifier for the pulsed current limit. Depending on the connected voltage (0 V...+10 V) a pulsed current from 0 A... Ipeak is adjusted, whereby Ipeak is the amplifier specific pulsed current. If the potentiometer for the internal peak current (P4) is not on the right limit stop, its position determines the upper limit. The current can be limited for both directions depending on the soldering bridges LB1, LB2 of the customer print, the external set limit is only active in case of the closed soldering bridge.
for MTRS 170-xx 17 25th March 2005 Release (14d), [14c] For the operation of the final stage a voltage of +15 V...+24 V has to be connected to this input, the internal voltage of +15 V can be used. If open this input is high impedance. The release function works only in case the transition from low to high is made in ready to operate. I²t-signal (16d), [16c] If the effective current limitation is active (yellow LED lights) this output provides +13 V. Motor connections, negative (18d,b,z, 20d,b,z), [18a,c, 20a,c] Terminal for the negative motor connection. Intermediate circuit, +Ucc (22d,b,z, 24d,b,z), [22a,c, 24a,c] Terminal for the positive pole of the DC voltage supply. The nominal value is 170 V DC, may be considerably lower depending on the motor used (see table 1.2, technical data). The ripple under load must not be higher then 50 V. Internally a condenser of 680:F is available. Intermediate circuit, PGND (26d,b,z, 28d,b,z), [26a,c, 28a,c] Terminal for the negative pole of the DC power supply. This point is connected galvanically to AGND in the amplifier. PGND should be connected as near as possible to earth. Motor connection, positive (30d,b,z, 32d,b,z), [30a,c, 32a,c] Terminal for the positive motor connection. 2.3 Minimum load inductivity The pulse width modulated final stage of the regulator needs for a correct function a minimum load inductivity as mentioned in table 1.1.
for MTRS 170-xx 18 25th March 2005 2.4 Polarisation of tacho and motor To be sure of the correct connection of the motor and its tacho generator only an easy voltage measurement on the switched-off unit is necessary. Needed is a voltmeter with indication of the polarity. The motor shaft must be turned by hand into one direction. A voltage is originated in the motor cable (pin 22 ac) and the tacho cable (pin 4 ac) against mass (pin 20 ac). The polarity of the voltages must be opposed. If this is not the case either the motor cables (pin 22 ac with 24 ac) or the tacho cables (pin 4 ac with 6 c) have to be changed. In case of a wrong connection of the motor it will turn uncontrolled at maximum speed and the set value has no influence. If the amplifier is operating and the motor turns in the wrong direction, both the motor and the tacho generator lines have to be modified. 2.5 Wiring according EMF All control cables have to be screened. The screen of the control cable must be connected to the control unit and not to the amplifier. If the screen is earthed at both ends the advantages of the set value differential input are lost and, additionally, interferences may arise. The motor line should consit of a three-core separate, shielded cable with a minimum section of 1.5 mm 2 : The shield should be connected to the power mass of the amplifier. The cores of any chokes should also be connected to the earth of the amplifier in order to avoid malfunction. 2.6 Input test circuit (next page) In order to check the correct connections of the amplifier the following input test circuit can be used. The indicated chokes are only necessary in case the motor has not enough inductivity (see table 1.1) 2.7 Connection (next page) This drawing shows only one of many possibilities to connect the amplifier depending on the individual requirements. If possible always a three-phase intermediate voltage power supply should be used (as indicated), in one-phase supply considerable currents will flow, charging mains, condensers and rectifiers.
for MTRS 170-xx 19 25th March 2005 2.6 Test circuit
for MTRS 170-xx 20 25th March 2005 2.7 Connection
for MTRS 170-xx 21 25th March 2005 3. INITIAL OPERATION Due to the extended regulation range the initial operation is in most cases very easy. With basic understanding, experience and an oscilloscope most of the adjustment work can be executed in the final machine. However this work has to be done as described in the part test circuit. See further details hereunder. 3.1 Adjustment of pulsed- and effective current limits. If the loading capacity of the motor is below the nominal current of the amplifier it has to be adapted. Also the pulsed current can be to elevated for some purposes. Both can be adjusted at the same time Instead of the motor in the test circuit a choke with the minimum inductivity should be connected in series with an ammeter. The inductivity of the choke must be constant up to the desired pulsed current limit (consider saturation limit). For the adjustment of the pulsed current on potentiometer P4 a voltage of +10 V has to be connected to input 12z (against 10d), the soldering bridges LB1, LB2 must be closed. Furthermore a constant speed set value of minimum 1 V is needed (input 12 d against 10 d). After switching on the power supply and release the adjusted pulsed current limit will flow and can be modified with P4 (Ipeak). Once the time has elapsed the current returns to the effective current limit adjusted with P1. If there is not enough time for the adjustment the amplifier has to be disabled and released after 15 minutes pause, thereafter the adjustment can be continued. With a reversed speed set voltage the symmetry should be controlled and averaged. Once the pulsed current limit is set the effective current can be adjusted with P1 moving it straight in one direction, whereby the amplifier reacts with a short pulsed or zero current before reaching its new regulation. 3.2 Tacho adjustment After the connection of the amplifier (see test circuit), the switch on and release a speed set value of 10 V has to be applied to input 12d against 10d. The speed of the motor must be adjusted with potentiometer P2 (tacho) to the required final speed. If the range of the potentiometer is insufficient the fixed resistor on the customer print has te be modified. 3.3 Offset adjustment With the warmed up device and the set up value input short circuited and connected to 0V-potential (interconnect 12d, 10d an 10z) the standstill of the motor can be adjusted with potentiometer P 201.
for MTRS 170-xx 22 25th March 2005 3.4 Total amplification A correct adjustment of the total amplification using the test circuit has to be done with the motor and a mounted flywheel mass with the same inertia as later used in the machine. Unfortunately this simulation is sometimes to inaccurate as this procedure neither can simulate the elasticity nor the friction of the load. Furthermore motors with mounted flywheel masses often show distinctive resonances impeding a correct adjustment. The adjustment should therefore be made if possible in the used machine. In a simple case the hearing is sufficient. With the unit switched on and the set value 0 V (motor standstill) the potentiometer P3 (AC-gain) should be turned to the right until an oscillation starts (depending of the charge inductivity 50...150 Hz). Then turn back immediately (before I²t gets active). From the stop point of the oscillation one turn back to the left - finish. In case of difficult load situations (e.g. elasticities) a dual channel oscilloscope has to be connected to the test points TP2 (tacho) and TP1 (I-actual value). Reference point is AGND (pin 10z) or TP7. Make short start/stop pulses, i.e. rectangular speed bounces. With potentiometer P3 the bounce response can be optimized. The target is the quickest possible run in of the tacho voltage to the peak value adjusted with the set value but without overshoot. The tendency to overshoot and instability can be easier seen with the current actual value than with the tacho signal.
for MTRS 170-xx 23 25th March 2005 4. OPTIMIZATION OF THE REGULATION BEHAVIOUR WITH THE CUSTOMER PRINT In rare occasions certain device features have to be adapted to the customer application. For this purpose there exist on the customer print easily interchangeable components. The position of those components can be found an the drawing hereunder. 4.1 Soldering bridges As mentioned above there exist several soldering bridges on the customer print. In total there are 3; LB1 and LB2 have to be closed, if the pulsed current limit should be adjusted externally through the input 12z ( current limit ). In case of open bridges the amplifier doesn t react to connected control voltages. Each bridge is responsible for one current direction, i.e. only one bridge can be closed. The soldering bridge LB4 must be closed if a dynamic brake is used. LB3 is not used.
for MTRS 170-xx 24 25th March 2005 4.2 Tacho filter The condenser C1 is responsible for the filtering of the tacho signal. The effective pre resistor has a value of 4,7 ks. The standard value of the condenser is 10 nf. In case of need the condenser can be enlarged, e.g. if the tacho signal is heavily disturbed with spikes or in case of use of the tacho monitoring. Unfortunately the filter deteriorates the regulation characteristics especially the overshoots after set value bounces. The overall amplification has to be reduced in this case. 4.3 Tacho scaling The resistor R1 allows to use the amplifier with a broad range of tacho voltages. With regard to a small drift the resistor should be selected in a way that the pickoff of the tacho potentiometer in case of a correctly adjusted amplifier is at a short distance of the right stop. With the voltage constant of the tacho generator in V/r.p.m./min. the desired speed n Nom and a speed set value of 10 V the resistor has a value of: R1 = 51.7 ks U set / (2.25 n Nom K E - U set ) With a set value of 10V, 3000 r.p.m. nominal speed and a tacho constant of 6 V/1000 r.p.m. the ideal value will be 16,95 kohm. With regard to the position of the potentiometer near the right stop a smaller value should be selected. The range of the potentiometer has a proportion of 1:6, with R1 = 10 ks (standard value) the unit will operate without problems.
for MTRS 170-xx 25 25th March 2005 4.4 Amplifier as current regulator In some applications there is an external speed regulation, the value input should in these cases be interpreted as current set value. The device can be changed to this operation mode with a few modifications on the customer print: R1 (tacho - pre-divisor): 0 Ohm C2 (integration condenser): bridged with wire R7 (proportional amplification): 20 ks P3 (AC-Gain): left stop The other components for special features of the speed regulation must not be modified (in standard unit) as there are almost no influences in the current regulation mode. Above mentioned configuration can be delivered ex factory upon request. 5. OPTIONS 5.1 Ballast circuit If the motor is braked by the amplifier a big part of the stored kinetic energy of the turning load is reconverted into electrical power. The same happens if the motor has to absorb permanently power e.g. on the output side of a coiling machine. In both cases the intermediate circuit voltage rises above the neutral value. Unfortunately the storing capacity for this energy is relatively low (approx. 9 Joule compared to the capacity of the ballast circuit: 1150 Joule), so even in very normal braking situations the voltage can reach dangerous regions. In order to avoid damages the final stage is switched off at 250 V DC by the internal excess voltage protection. In order the keep the normal operation active the rise of the intermediate circuit voltage has to be avoided by external means. This is the use of a the ballast circuit. In order to store short cycled brake energy basically condensers would be suitable. The stored energy could be used during the following acceleration cycle. Unfortunately even in case of a low mass inertia relatively big (i.e. expensive) condensers would be needed. Furthermore this method is unsuitable in case of permanent brake energy. A retransfer to the mains is neither possible as the rectifiers (for cost reasons) are uncontrolled bridge-types (current only possible in one direction). It remains to convert the energy into heat by power resistors. The value of the intermediate circuit voltage is compared with a precision reference voltage. In case of trespassing the threshold voltage (data see table) power resistors are switched in parallel to the intermediate circuit by IGBT s. A hysteresis between the switch off and switch on point provides a clean and low loss connecting. The internal protection circuit monitors the switch-on time and the mean value of the current an limits if necessary the function: only in case of overloading of the ballast circuit the connected amplifier switches off for excess voltage.
for MTRS 170-xx 26 25th March 2005 Normally the ballast circuit can be used for several amplifiers connected simultaneously to the intermediate circuit. It has to be checked if the pulsed current power of the ballast circuit is sufficient if all the axes are braked at the same time. A parallel connection of several ballast circuits is possible. The power in this case will be shared unequal. In a first moment the unit will operate which has as a consequence of material tolerances the lowest threshold. With higher braking charge the unit with the following threshold will be active and so on. The unit with the highest threshold will take the rest. Overloading of a single unit is excluded. Switch on threshold 235 VDC Switch off threshold 220 VDC Current during operation 20 A Pulsed charge 4,6 kw Max. pulsed power (without pre-charge) 1.150 Joule (20 A, 230 V, 0,25 s) Integration time constant 10 s Average power 100 Watt Connector DIN41612, form D32 Connection, positive 2c, 4c, 6c, 8c, 10c, 12c, 14c Connection, negative 2a, 4a, 6a, 8a, 10a, 12a, 14a, 16a- 32c 5.2 Tacho monitoring This circuit, optionally available upon demand, prevents an uncontrolled acceleration of the motor in case of a malfunction of the tacho. In case of an interruption or a mass short circuit the amplifier will indicate malfunction whereby the connected motor slows down without current or is braked with the dynamic brake. The circuit is conceived in a way that the tacho generator receives potential free a medium frequent AC the presence of which is controlled at the cold end of the tacho line. The carrying frequency has been selected the way that on one hand there is just no influence of the amplifier possible and on the other hand the capacity of long screened tacho lines will not disturb. In critical cases (long lines, high inductive tacho) a test circuit has to be made with the original tacho and cable to the sensitivity of the wiring. The tacho monitoring is installed in the basic unit instead of the auxiliary voltage supply. This means that an external voltage supply of + 15 V has to be used. A further disadvantage is that some tacho s tend, due to their construction to the formation of a powerful offset voltage with low stability. As a consequence of these disadvantages it should be considered to conceive the simple bipolar tacho line very carefully avoiding line breaks. Modern applications often allow to monitor the motor function with software.
for MTRS 170-xx 27 25th March 2005 5.3 Dynamic brake In some applications the motor has to be braked down in case of emergency stop or malfunction independently of the amplifier. Therefore a special output is provided for the control of a dynamic brake. The circuit contains 2 antiparallel wired thyristor in series with a low impedance power resistor. Without activation the thyristor is charged by the FEM of a turning motor and brakes. Only in case of operation of the amplifier (final stage active) the dynamic brake receives a signal and the thyristor remains inactive. Thus the self safety (e.g. in case of a mains breakdown) is guaranteed. As a consequence of the lock of the thyristor once ignited the absolute standstill of the motor has to be awaited until the rerelease of the amplifier, if not the final stage will operate against the brake resistor an destroy it. In case the soldering bridge for the use without brake is open the often troublesome delay will not apply.
for MTRS 170-xx 28 25th March 2005 6. DRAWINGS 6.1 Plan of components, surface
for MTRS 170-xx 29 25th March 2005 6.2 Plan of components, bottom side
for MTRS 170-xx 30 25th March 2005 6.3 Plan of components, ballast circuit
for MTRS 170-xx 31 25th March 2005 6.4 Dimensions