Earth fault

What does F00021 mean?

An earth fault has been detected, indicating an insulation breakdown where current is flowing to ground. This occurs when the sum of the phase currents exceeds 5% of the inverter's nominal current, potentially causing personnel hazard, equipment damage, or fire if left unresolved.

• Breakdown of motor winding insulation to the motor frame (ground).
• Damage to the motor cable insulation (e.g., due to abrasion, crushing, or chemical exposure) causing a short to ground.
• Water ingress or condensation inside the motor or terminal box leading to a conductive path to ground.
• Accumulation of conductive dust or debris on internal drive components or motor connections.
• Incorrect cable shielding or grounding leading to stray currents being interpreted as an earth fault.

Click steps to track your progress.

1. 1

   Disconnect the motor cables (U, V, W) from the drive output terminals and perform an insulation resistance test (e.g., megohmmeter at 500VDC) between each motor phase and ground at the motor cable end.

2. 2

   If the motor cable insulation resistance is low, disconnect the motor from the cable and retest the motor insulation (phase to ground) and the cable insulation (phase to ground) separately.

3. 3

   Inspect the motor terminal box and drive output terminals for any signs of moisture, conductive debris, or damaged insulation on connections.

4. 4

   Verify proper grounding of the motor frame and the drive chassis to the main plant earth busbar (e.g., resistance below 0.1 Ohm).

5. 5

   Check the motor cable routing for any mechanical damage, pinching, or tight bends that could compromise insulation.