GE Industrial Solutions AF-600 FP High Power (460V_575V 150HP and above) - Manual (Page 97)

7. In sequence, connect the positive (+) meter lead to the frequency converter output terminals U, V, and W. The meter should indicate a diode drop.
8. Leave the negative meter lead connected to cable MK105, and run the frequency converter at 30 Hz.
9. In sequence, again connect the positive (+) meter lead to the frequency converter output terminals U, V, and W. The meter should effectively indicate a
short circuit or around a 0.035 diode drop which indicates upper IGBTs are turned on and shorting the meter to a positive bus.
NB!
Some voltage leakage within the unit may cause the meter to indicate a small negative voltage drop.
Incorrect Reading
An incorrect reading indicates some of the IGBTs are not turning on. Replace the IGBT module according to the disassembly instructions in Section 7 or 8.
6.3.13 Brake IGBT Test
Use the signal test board to test the operation of the dynamic brake IGBT and gate drive circuitry. The following procedure can be used to force the brake circuit
to activate for testing.
1. Connect the signal test board to connector MK104 on the control card.
2. Set the voltage test switch labelled Over V to the ON position.
3. Turn the potentiometer on the test board until the brake circuit activates. This causes the brake IGBT to turn on and off at approximately 1.2 KHz. Duty
cycle (pulse width) increases as the potentiometer is increased.
4. Using an oscilloscope or DVM, measure at terminal 13. Terminal 13 represents the gate signal to the brake IGBT. This should be 4.04 VDC when brake is
OFF and drop to zero when brake is ON.
5. Use an oscilloscope or DVM at terminal 14. Terminal 14 is a logic level (5V) signal representing voltage across brake IGBT. This should measure 5.1 VDC
when brake is OFF and drop to zero when brake is ON.
Incorrect Reading
If the signal on terminal 13 is not correct, first check that the frequency converter is correctly programmed for dynamic braking (parameter B-10). If the pro-
gramming is correct, replace the control card in accordance with procedures in Section 7 or 8.
If the signal on terminal 13 is correct but the signal on terminal 14 is not, the brake IGBT gate signal must be checked to determine whether the fault lies in the
IGBT or the gate drive card. See Gate Drive Signal Tests.
6.3.14 Current Sensors Test
The current sensors are Hall effect devices that send a signal proportional to the actual output current waveform to the power card. The current scaling card,
attached to the power card, scales the signals from the current sensors to the proper level for monitoring and processing motor control data. A defective current
sensor can cause erroneous earth faults and overcurrent trips. In such instances, the fault will usually only occur at higher loads. If the incorrect current scaling
card is installed, the current signals will be improperly scaled. This could cause erroneous overcurrent trips. If the current scaling card is not installed, the frequency
converter will trip.
A couple of simple checks can be made to determine the status of the sensors.
1. Apply power to the frequency converter.
2. Ensure that motor check, pre-magnetizing, DC hold, DC brake, or other parameter setups are disabled that create a holding torque while at zero speed.
Current displayed will exceed 1 to 2 amps if such parameters are not disabled.
3. Run the frequency converter with a zero speed reference. Note the output current reading in the display. The display should indicate approximately 1
to 2 amps.
If the current is greater than 1 to 2 amps and a current producing parameter is not active, the test will need to be made again with the motor leads disconnected.
4. Remove power from the frequency converter. Monitor the DC bus voltage at power card connector MK105 (A) and (B) to ensure the bus is fully discharged.
5. Remove the output motor leads from terminals U, V, and W.
6. Apply power to the frequency converter.
7. Run the frequency converter with a zero speed reference. Note the output current reading in the display. The display should indicate less than 1 amp.
AF-650 GP and AF-600 FP High Power Service Manual
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