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What can be done to troubleshoot a Transistor Short C or GF fault on an ATV66?

Published date: 10 June 2020

ATV66 has a Transistor Short C or GF Fault.
Product Line:
ATV66 drives
Transistor Short Circuit or GF


This fault appears if the self-test of the inverter bridge (which occurs only on power up of the drive controller) detects what appears to be a shorted output transistor. During this self-test, each individual output transistor is gated. If a desaturation fault is returned by the gate drive board of that transistor, it is assumed that the other transistor in that phase is shorted or is permanently gated on. This test stops as soon as a faulted transistor is found. No further testing is performed to find other shorted transistors. This test lasts for about 100 ms and takes place before the autotune pulse to the motor is processed.

Disconnect the motor and cables from the output terminals of the drive. Go to menu 7.4 and set Out phase loss to NO. Cycle power and attempt to run the drive

If it faults on Trans Short C or GF, then it is likely there could be a problem in the drive output transistors or gate driver boards.

If it runs without faulting, run it at 15, 30, 45, and 60Hz and at each speed check the phase to phase output voltage with a true RMS meter rated for 1000 VAC. If the voltages at any speed are within a couple volts of each other, the drive is OK, and you need to check the motor and cables with a 1000VDC megger.

Refer to Bulletin No. VD0C06S701 or VD0C06S702 for more information on checking the inverter section and IGBTs of the drive.


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