Output side earth (ground) fault overcurrent at start

What does E.GF mean?

This fault indicates an output side earth (ground) fault overcurrent detected during inverter startup on the load side. It signifies a critical insulation breakdown in the motor or its connecting cables, posing a significant safety hazard and risk of equipment damage. This protection is configurable via Pr. 249.

• Insulation breakdown between one or more motor phases and the motor frame (ground).
• Insulation damage in the motor cable (U, V, W to motor ground/shield) due to mechanical abrasion or aging.
• Water ingress or contamination in the motor terminal box or cable glands, creating a conductive path to ground.
• Loose ground connection between the motor frame and the main facility ground, leading to spurious ground current detection.
• Internal short to ground within the inverter's output stage (IGBTs) or internal output wiring.

Click steps to track your progress.

1. 1

   Disconnect the motor cables (U, V, W) from the inverter output terminals. Attempt to run the inverter without the motor.

2. 2

   Using a megohmmeter (insulation resistance tester), measure insulation resistance from each motor output phase (U, V, W) to motor frame ground (PE). Values should typically be greater than 1 MOhm.

3. 3

   Visually inspect the entire length of the motor cable for any visible damage, cuts, or crushed sections.

4. 4

   Check for moisture or debris inside the motor terminal box and ensure all connections are clean and dry.

5. 5

   Verify the integrity and continuity of the protective earth (PE) connection from the inverter chassis to the motor frame.