GFF Ground Fault fault in delta drive

GFF Ground Fault fault in delta drive troubleshooting

Description

The GFF fault indicates the drive has detected a current leakage to ground (Earth) from the output terminals. The drive measures the sum of currents (U+V+W); if the sum is not zero, current is leaking elsewhere.

Causes

1. Motor Insulation Failure: The motor winding insulation has degraded, shorting a phase to the motor housing.
2. Cable Damage: The output cable insulation is cut or chafed, touching the conduit or cable tray.
3. Moisture: Water has entered the motor terminal box or the conduit.
4. Long Cables: Extremely long motor cables can have high parasitic capacitance to ground, which the drive sees as leakage.

Solution

Critical safety check required:
1. Megger Test: Disconnect the motor cables from the drive. Use a 500V or 1000V Megohmmeter (Megger) to test resistance between each motor phase and Ground. A reading below 1-2 Megaohms indicates a fault.
2. Inspect Cable: Visually check the cable run for cuts or water ingress.
3. Test Drive: Run the drive without the motor connected. If GFF persists, the fault is inside the drive (current sensor drift), requiring repair.
4. Carrier Frequency: Reducing carrier frequency can sometimes reduce leakage current capacitance on long cable runs.