Mitsubishi E.OC1: Mitsubishi FR-A800 Error Code E.OC1

Symptoms

The drive trips immediately during acceleration. The operation panel displays E.OC1, indicating an overcurrent condition occurred while accelerating. The motor coasts to stop and the output is cut off.

Possible Causes

Acceleration time too short causing excessive current draw
Short circuit or ground fault on the motor output side
Motor winding insulation failure causing short
Load torque much higher than expected during startup
IGBT module or current detection circuit hardware fault

Troubleshooting Steps

Step 1: Inspect motor and output cable insulation with a megger tester
Insulation resistance should exceed 1Mohm; replace motor or cable if below
Step 2: Verify the acceleration time setting in parameter Pr.7
Increase Pr.7 value if the time is too short for the load inertia
Step 3: Disconnect the motor and run the drive in no-load mode
If E.OC1 persists without motor, the drive IGBT or detection circuit is faulty
Step 4: Measure IGBT module resistance between phases with the motor disconnected
All phase-to-phase readings should be roughly equal; a low reading indicates a shorted IGBT

How to Reset

To reset: 1) Clear the fault by pressing STOP/RESET on the operation panel or cycling power. 2) Fix the root cause (cable, motor, parameter). 3) Re-start the drive. Caution: Do not repeatedly reset without fixing the cause, as overcurrent can damage the IGBT module.

Common Replacement Parts

R60BZ: FR-A800 IGBT module replacement (Must match the exact drive model rating; factory replacement recommended)

Frequently Asked Questions

Q: What is the difference between E.OC1, E.OC2, and E.OC3?
E.OC1 is overcurrent during acceleration, E.OC2 during deceleration, and E.OC3 during steady-speed operation. Each points to a different stage of the drive cycle where the overcurrent was detected.
Q: Can a long motor cable cause E.OC1?
Yes, excessively long motor cables increase capacitance and leakage current, which can trigger overcurrent during acceleration. Use a sine wave filter or output reactor for cables over 30m.

Mitsubishi FR-A800 Error Code E.OC1