Mitsubishi E.OC3: Mitsubishi FR-A800 Error Code E.OC3

Symptoms

The drive trips during steady-speed running. The panel displays E.OC3, indicating an overcurrent was detected while the motor was running at constant speed without accelerating or decelerating.

Possible Causes

Sudden mechanical load increase or shock load during operation
Motor insulation degradation causing intermittent short between phases
Output cable damage or loose terminal causing arc faults
Drive IGBT module thermal or electrical degradation under sustained load

Troubleshooting Steps

Step 1: Check for sudden mechanical changes in the load
No unexpected load changes or jamming in the driven equipment
Step 2: Measure motor winding resistance across all three phases (U-V, V-W, U-W)
All three readings should be balanced within 5% of each other
Step 3: Inspect output terminals and cable connections for tightness and signs of arcing
All terminals torqued to specification, no discoloration or burn marks
Step 4: If the motor and cable check out, the drive IGBT module may be degraded
Run with a known-good motor to confirm; if still tripping, IGBT replacement needed

How to Reset

To reset: 1) Press STOP/RESET on the panel or cycle power. 2) Investigate and resolve the load or insulation issue. 3) Restart the drive. Caution: E.OC3 during steady-speed often indicates a serious developing fault; investigate thoroughly.

Common Replacement Parts

R60BZ: FR-A800 IGBT module replacement (Match to drive rating; factory replacement recommended)

Frequently Asked Questions

Q: Why does E.OC3 happen during normal running?
Sudden load spikes, deteriorating motor insulation, or aging IGBT modules can all cause overcurrent during steady-speed operation. It is more serious than E.OC1 because it occurs without any speed change.

Mitsubishi FR-A800 Error Code E.OC3