Earth fault

What does 3 mean?

The drive's current measurement system has detected that the sum of the motor phase currents is not zero, indicating a leakage current to earth. This is typically a result of insulation malfunction within the motor windings or the motor cables. An unresolved earth fault poses a significant electrical safety hazard and can cause severe damage to both the motor and the drive.

• Insulation breakdown in the motor windings due to aging, moisture ingress, or overheating, causing current leakage to the motor frame (earth).
• Damaged motor cable insulation (e.g., cut, chafed, or waterlogged) allowing current to leak to the cable shield or conduit (earth).
• Accumulation of conductive dust or moisture within the motor terminal box or drive output terminals (U, V, W) creating a leakage path.
• Incorrect grounding of the motor or motor cable shield, preventing proper fault current return paths.
• Defective internal current sensor or earth fault detection circuit within the drive itself.

Click steps to track your progress.

1. 1

   Disconnect motor cables from the drive output terminals (U, V, W) and perform an insulation resistance test (megohmmeter) on the motor cables to earth at 500VDC.

2. 2

   Disconnect motor cables from the motor terminal box and perform an insulation resistance test (megohmmeter) on the motor windings (each phase to frame) at 500VDC.

3. 3

   Inspect the motor terminal box for signs of moisture, conductive dust, or physical damage to internal wiring and connections.

4. 4

   Verify the motor frame is properly earthed (grounded) to the main potential equalization busbar and that the motor cable shield is correctly terminated at both ends.

5. 5

   Inspect drive output terminals (U, V, W) for any signs of arcing, carbon tracking, or conductive debris.