How to Fix Mitsubishi FR-A800 Fault E.GF Ground Fault Guide

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Staring at E.GF on your Mitsubishi FR-A800? Learn why your drive detected a ground fault, how to test your motor insulation, and the steps to clear the error.

How to Fix Mitsubishi FR-A800 Fault E.GF Ground Fault Guide

 

Solving Mitsubishi FR-A800 Fault E.GF: The Ground Fault Guide

If your Mitsubishi FR-A800 has come to a screeching halt and the keypad is flashing E.GF, the drive has detected an "Earth Fault." Essentially, current is escaping from its intended path and leaking to the ground.

The A800 is a very sensitive drive; it monitors the balance between its output phases. If the math doesn't add up because some electricity is heading to the earth, it trips E.GF to prevent the drive's internal transistors (IGBTs) from blowing up. Let’s look at how to find the leak.

Common Causes of the E.GF Fault

When a Mitsubishi drive trips on E.GF, the problem is almost always "outside" the drive in the field wiring or the motor. Here are the usual suspects:

  • Motor Insulation Failure: The most common cause. The copper windings inside the motor have degraded and are touching the motor frame.
  • Damaged Motor Cable: The cable has been nicked, crushed, or heat-damaged inside a conduit.
  • Moisture and Contamination: Water or conductive "carbon black" dust has entered the motor terminal box.
  • Output Surge: A massive spike during start-up can sometimes trick the drive's sensors.
  • Internal Drive Failure: In rare cases, an internal current sensor or an IGBT has failed.

Step-by-Step Troubleshooting for E.GF

1. The "Isolation" Test (The Gold Standard)

Before you blame the motor, we need to prove the drive is healthy.

  • Power down and lock out the drive.
  • Disconnect the motor wires from the U, V, and W terminals.
  • Power the drive back up and try to "Start" it at a low frequency.
  • If E.GF still appears: The drive's internal sensors are damaged. You likely need a drive repair or replacement.
  • If the drive stays in "Run": The drive is fine! The problem is definitely in your cables or the motor.

2. Check for Moisture (The "First Response" Fix)

If your motor is in a wash-down area or a humid plant, check the terminal box.

  • Open the motor terminal box and look for water, condensation, or oil.
  • Clean and dry the box thoroughly with a heat gun or compressed air. Often, drying a damp terminal block is all it takes to clear an E.GF fault.

3. The Megger Test (Insulation Check)

If the drive is fine and the box is dry, you need to test the motor's internal health.
Crucial Warning: Never use a Megger (Insulation Tester) while the wires are still connected to the drive! The 1000V test signal will destroy the VFD instantly.

  • Disconnect the motor leads from the drive.
  • Check the resistance between each phase and the ground.
  • A healthy motor should read several hundred Megohms. If you read 0 Megohms or anything below 2 Megohms, your motor has an internal ground fault.

4. Adjust Parameter 249 (Earth Fault Detection)

The FR-A800 allows you to control how it handles ground faults via Parameter 249 (Earth fault detection at start).

  • By default, the drive checks for ground faults every time it starts.
  • If you have very long motor cables (over 100 meters), "capacitive charging" can sometimes cause nuisance E.GF trips.
  • Consult the manual before changing Pr. 249, but occasionally set it to "0" (to disable detection at start-up) if you have verified the motor is healthy with a Megger.

How to Reset the E.GF Fault

  1. Fix the damaged cable or replace the faulty motor.
  2. Cycle the power to the drive or press the RESET button on the keypad.
  3. If the fault happens exactly at the moment the motor starts to turn, double-check your output contactor (if you have one) for a burnt contact touching the ground.

Summary

The Mitsubishi FR-A800 E.GF fault is a hardware-saving feature. It prevents a small motor short from turning into a massive drive explosion. Follow the Isolation Test first—it will tell you within 5 minutes if you need a new motor or a new drive.

 

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