Seeking help regarding grounding fault of 75kw low-voltage variable frequency motor
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The motor can operate normally at low frequencies, but reports a ground fault at high frequencies. The wiring was disassembled to check, and the insulation was found to be in good condition. Help, what’s going on here?
After replacing the motor, it was fixed. But the cause of the failure has not yet been found.
Dear sea friend, it seems there must be a problem with the insulation quality of your motor! In particular, at a fundamental frequency of 50HZ, the speed control characteristic is such that the speed is directly proportional to the output voltage; as the speed increases (or the frequency rises), the output voltage of the inverter also increases accordingly, which means that the voltage that the motor windings can withstand also increases. Poor insulation of the motor windings, or damage and aging of the connection cables, can all lead to an increase in leakage current, thereby triggering the inverter’s grounding mechanism. You can try using a 1000V megohmmeter for testing (try not to use a 500V one), and compare the insulation level with that of the new motor; this might help you draw a conclusion!
Thank you, master! Do I need to rewire and replace the coils of the motor I’ve taken out?
It’s probably a problem with the drive circuit
Just replace the motor; there’s no problem with the circuit.
1. There may be a problem with the motor. 2. There is a problem with the cable circuit. 3. There is a problem with the IGBT board
This problem has been resolved; only a very small turn of that motor was burned out, and this does not affect low-frequency operation
Insulation aging can be addressed by repainting the insulation; motor leads can be replaced