Mitsubishi E.OV2: Mitsubishi FR-A800 Error Code E.OV2

Symptoms

The drive trips during deceleration. The panel displays E.OV2, indicating the DC bus voltage rose above the overvoltage threshold while the motor was decelerating. This is the most common overvoltage fault, caused by regenerative energy from the motor during deceleration.

Possible Causes

Deceleration time too short, causing excessive regenerative energy
No brake resistor installed or brake resistor is damaged
Brake transistor (built-in) is faulty
Input supply voltage already high, reducing the headroom for regenerative energy

Troubleshooting Steps

Step 1: Check the deceleration time setting in parameter Pr.8
Increase Pr.8 to allow more time for the motor to decelerate, reducing regenerative energy
Step 2: Inspect the brake resistor for continuity and correct resistance value
Resistor should read within 10% of its rated value; replace if open or shorted
Step 3: Verify the brake transistor operation by monitoring the DC bus voltage during deceleration
DC bus voltage should be clamped by the brake resistor; if it keeps rising, the brake transistor is faulty
Step 4: Measure the input supply voltage at idle
If already near 440V (400V class), there is little headroom for regenerative energy

How to Reset

To reset: 1) Press STOP/RESET. 2) Install or replace the brake resistor. 3) Increase deceleration time. 4) Restart. Caution: Without a brake resistor, repeated E.OV2 trips can damage the DC bus capacitors.

Common Replacement Parts

FR-BR-H2K2W: Mitsubishi brake resistor 2kW 2ohm (Match to drive capacity; see resistor selection table in the manual)

Frequently Asked Questions

Q: How do I calculate the correct brake resistor value?
Refer to the FR-A800 manual's brake resistor selection table. The resistor must handle the peak regenerative power and the duty cycle. Using an undersized resistor can cause it to overheat and fail.

Mitsubishi FR-A800 Error Code E.OV2