Earth (ground) fault

What does #14 mean?

An earth (ground) fault has been detected, indicating an unintended current path from a phase conductor to the ground. This usually points to damaged insulation in the motor windings or associated cabling, posing a significant safety hazard and a risk of severe damage to the drive or compressor components.

• Motor winding insulation breakdown due to aging, moisture ingress, or overheating, creating a direct path from a phase to the motor frame.
• Damaged motor cable insulation (e.g., crushed, abraded, cut) creating a short circuit path from a phase conductor to ground.
• Water or conductive dust contamination within the motor terminal box or drive enclosure causing a conductive path to ground.
• Faulty surge arrestor or line filter component (e.g., MOV, Y-capacitor) shorting to ground within the drive or input filter.
• Improper termination of shielded cables where the shield makes unintended contact with a phase conductor due to incorrect installation.

Click steps to track your progress.

1. 1

   Isolate power, disconnect motor cables from the drive, and perform an insulation resistance test (Megger) between each motor phase (U, V, W) and motor frame ground (PE). Values should be >1 MΩ.

2. 2

   Perform an insulation resistance test (Megger) on the motor cables from the drive output to the motor, between each phase and the cable shield/ground conductor.

3. 3

   Visually inspect the motor terminal box and drive output terminals for signs of arcing, moisture, or conductive debris accumulation.

4. 4

   Check the integrity of the motor cable conduit and glands for any signs of mechanical damage that could compromise insulation integrity.

5. 5

   Temporarily disconnect any peripheral devices or filters connected to the motor circuit (e.g., braking resistors, dV/dt filters) and re-test for the fault.