Delta MS300
The drive reports a ground fault (GFF) on start; the fault persists although the motor and cable are healthy.
Faulty — board out of service
Repaired — tested under load
Fault
The drive reports a ground fault (GFF) on start; the fault persists although the motor and cable are healthy.
Analysis
Motor and cable insulation megger-tested healthy; the fault pointed to the internal current-sensing (hall sensor) circuit. One phase current sensor's offset had drifted.
Repair Steps
- 1Motor/cable verification
Phase-to-ground insulation >1 MΩ; external fault ruled out.
- 2Current-sensing circuit
Hall-sensor supply and offset measured; drifting sensor identified.
- 3Component replacement + calibration
Sensor replaced and offset calibrated.
Changed Components
- Phase current hall sensor
- Related signal capacitors
Test Result
GFF did not recur; three-phase current readings balanced.
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