Earth Fault

What does 4 mean?

An earth fault (ground fault) has been detected in the motor or the cabling between the drive and the motor. This indicates current leakage to ground, which is a serious safety hazard and can cause significant damage to the drive or motor if not resolved promptly.

• Degraded insulation in the motor windings due to age, moisture ingress, or mechanical stress.
• Damage to the motor cable insulation (e.g., crushing, abrasion, chemical exposure) creating a path to ground.
• Water or conductive dust ingress into the motor terminal box or drive output terminals (U, V, W).
• Incorrectly grounded motor frame or cabinet, leading to stray current paths.
• Leakage current from output filter components if a non-standard filter is used.

Click steps to track your progress.

1. 1

   Disconnect the motor cables from the drive's output terminals (U, V, W) and then power cycle the drive to see if the fault clears.

2. 2

   Perform an insulation resistance test (Megger test) on the motor windings to earth (motor frame) with a 500VDC Megger, expecting >1 Megaohm.

3. 3

   Perform an insulation resistance test on each motor cable phase (U, V, W) to earth along the entire cable run with a 500VDC Megger.

4. 4

   Visually inspect the motor terminal box for moisture, corrosion, or signs of arcing.

5. 5

   Check continuity between the motor frame and the main earthing point of the control cabinet.