Mitsubishi VFD Fault Codes: Causes and Fixes for Common FR-Series Alarms

When a Mitsubishi Electric FR-series drive trips, the display shows an error code beginning with E.. Knowing what each code means lets your maintenance team fix most trips in minutes instead of waiting for an engineer. This guide covers the Mitsubishi VFD fault codes we see most often in the field, across FR-D700, FR-E700/E800, FR-F800 and FR-A800 drives.

Safety first: after switching off the supply, wait for the charge lamp to go out and confirm the DC bus voltage is safe (at least 10 minutes, as stated in the manual) before touching the terminals.

Overcurrent trips: E.OC1, E.OC2, E.OC3

The drive saw output current above its protection level. The number tells you when it happened:

• E.OC1 during acceleration
• E.OC2 at constant speed
• E.OC3 during deceleration or stop

What to check: acceleration/deceleration time too short (Pr.7/Pr.8); torque boost set too high (Pr.0); a jammed or overloaded machine; a short circuit or ground fault in the motor cable; the motor started while still coasting. If E.OC appears instantly with the motor disconnected, the output transistors (IGBTs) are likely damaged and the drive needs repair.

Regenerative overvoltage: E.OV1, E.OV2, E.OV3

The DC bus voltage rose too high, usually because the motor is feeding energy back into the drive.

• E.OV1 during acceleration, E.OV2 at constant speed, E.OV3 during deceleration

What to check: deceleration time too short for the load inertia; an overhauling load such as a vertical axis or downhill conveyor; high supply voltage or voltage surges. Fixes include longer deceleration, enabling the regeneration avoidance function, or adding a braking resistor or brake unit.

Overload: E.THM and E.THT

• E.THM (motor overload): the electronic thermal relay for the motor operated. Check that Pr.9 is set to the motor's rated current, look for mechanical overload, and check whether a self-cooled motor is running at low speed for long periods.
• E.THT (inverter overload): the drive itself is overloaded. The drive may be undersized for the load, or the load has increased (worn bearings, tight chains, product build-up).

Supply problems: E.UVT and E.ILF

• E.UVT (undervoltage): the supply voltage dropped. Check incoming supply, loose terminals, a weak supply transformer, or large motors starting on the same feeder.
• E.ILF (input phase loss): one input phase is missing (on models and settings where this protection is enabled). Check fuses, MCB and contactor contacts.

Wiring and motor faults: E.GF and E.LF

• E.GF (output side ground fault overcurrent): current is leaking to earth on the output side. Megger the motor and cable (with the drive disconnected). Moisture in the terminal box is a common cause after monsoon.
• E.LF (output phase loss): one motor phase is open. Check motor cable, terminals and the motor winding.

Temperature and stall: E.FIN and E.OLT

• E.FIN (heatsink overheat): clean the heatsink and fan, check the cooling fan works, and reduce panel temperature.
• E.OLT (stall prevention stop): the drive kept limiting current to avoid a trip and the motor stalled. Reduce the load or review the stall prevention settings.

Quick troubleshooting table

When to call for drive repair

If a trip repeats immediately after reset with the motor disconnected, if the display is blank, or if you see burnt components or a swollen DC bus capacitor, the drive needs component-level repair. Do not keep resetting a drive with an internal fault; it can cause further damage.

AB Automation's factory-trained engineers provide AC/DC and servo drive repair for Mitsubishi and all major brands, with standby drives available to keep your line running. Call +91 90331 37026 or send us the fault code and drive model.