Output side ground fault overcurrent protection
Mitsubishi Electric · FR-E500 Inverter
What does Ground Fault mean?
This function stops the inverter output if a ground fault overcurrent (alarm output E.GF) is detected on the inverter's output (load) side, affecting the motor or its connection cable. This protection can be enabled or disabled at inverter startup using Pr. 249. If enabled (Pr. 249=1), there will be an approximate 20ms output delay at every start.
Common Causes
- Ground fault in the motor windings or motor insulation breakdown.
- Ground fault in the motor connection cable due to damaged insulation, moisture ingress, or improper wiring.
- Incorrect setting of Pr. 249 'ground fault detection at start', leading to detection at startup when not desired.
- Motor capacity less than 0.1kW, potentially affecting ground fault detection reliability.
Repair Steps & Checklist
Click steps to track your progress.
- 1
Measure insulation resistance between motor phases (U, V, W) and ground using a megger to identify the exact location of the ground fault.
- 2
Inspect the motor connection cable for any signs of insulation damage, chafing, or improper routing.
- 3
Verify the setting of Pr. 249 (ground fault detection at start); set to '0' if startup detection is not required or causing nuisance trips.