Ground Fault

What does GF mean?

The ground fault detection circuit monitors output current and activates when one of the inverter output phases is connected to ground, or the grounding current exceeds 50% of the inverter rated current. This condition poses a serious electrical hazard, risks personnel safety, and can damage the inverter and connected motor if not resolved promptly.

• Insulation breakdown in the motor windings (phase-to-ground) due to aging, moisture, or overheating.
• Damaged motor cable insulation allowing a phase conductor to contact the cable tray or machine frame.
• Water ingress or condensation inside the motor terminal box or inverter output section.
• Faulty surge arrestors or EMI filters on the inverter output creating a path to ground.
• Incorrectly wired or damaged output contactor or disconnect switch with a ground fault.

Click steps to track your progress.

1. 1

   Disconnect power to the inverter and ensure the DC bus capacitors are discharged (wait 5-10 minutes).

2. 2

   Disconnect motor cables (U, V, W) from the inverter output terminals.

3. 3

   Measure insulation resistance of each motor phase to ground using a megohmmeter (e.g., 1000V DC test voltage).

4. 4

   Measure insulation resistance of the motor cables from the inverter side to the motor side (phase-to-ground).

5. 5

   Check for moisture or foreign conductive material inside the motor terminal box or inverter output compartment.

6. 6

   If the fault clears with the motor disconnected, inspect the motor for internal ground faults and the motor cables for damage.