Ground Fault

Was bedeutet Ground Fault ?

The ground leakage current on the drive's output side has surpassed 50% of the drive's rated output current. This often indicates damaged motor or cable insulation, or excessive stray capacitance due to long cable runs. This condition poses a serious electrical safety hazard and potential damage to the motor or drive.

• Damaged insulation on the motor output cables (U, V, W) to ground, potentially due to mechanical abrasion, crushing, or chemical exposure.
• Internal insulation breakdown within the motor windings (U, V, W phases) to the motor frame (ground) due to overheating or aging.
• Water ingress or excessive moisture in the motor or terminal box, reducing insulation resistance to ground.
• Excessive cable length between the drive and motor, leading to high stray capacitance to ground, especially with unshielded cables.
• Incorrectly terminated or damaged motor cable shield, allowing leakage currents to flow to ground.
• Drive's ground fault detection sensitivity (e.g., Parameter L2-03) is set too high for the application, especially with multiple motors or long cables.

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1. 1

   1. Power down the drive completely (wait for DC bus discharge). Disconnect all motor leads (U, V, W) from the drive's output terminals.

2. 2

   2. Perform an insulation resistance test (Megger test at 500-1000VDC) on each motor phase (U, V, W) to the motor frame ground. Reading should be >1MΩ, ideally >100MΩ.

3. 3

   3. Inspect the entire length of the motor cable for any visible damage to the outer jacket or signs of wear that could compromise insulation.

4. 4

   4. Measure the insulation resistance of the motor cable from each conductor (U, V, W) to the cable shield/ground.

5. 5

   5. Verify the motor cable shield is correctly terminated and grounded at both the drive and motor ends. Ensure no stray strands are touching ground.

6. 6

   6. If the ground fault detection parameter (e.g., L2-03 'Ground Fault Detection Level') is adjustable, slightly reduce its sensitivity if the cable length is excessively long (over 50m) and insulation is verified good.