VFD Overcurrent Trip: Causes & How to Fix It

An overcurrent (OC) trip means the drive's output current exceeded its protection threshold, and the most common causes are an acceleration ramp too short for the load, wrong motor parameters, a damaged motor or cable, or a mechanically jammed machine. The fastest fix path: check the trip timing, run motor autotuning, lengthen the acceleration time, and inspect the motor and cable insulation. This article explains how OC protection works, the causes, and a step-by-step diagnosis with prevention settings.

How Overcurrent Protection Works

The drive continuously compares its output current with the limit set by the overload class and the current-limitation parameter. A trip fires in two cases: an instantaneous overcurrent (usually a hardware fault, e.g. a short circuit or a faulty IGBT) or an overcurrent over time (usually a control issue – the motor draws more than the drive can deliver). IEC 61800-5-1 requires the drive to protect itself and the motor within defined limits, which is why OC trips are designed to be fast and safe rather than to indicate damage.

Common Causes of Overcurrent Trips

• Acceleration too fast: the ramp time is shorter than the load can follow; current rises to the limit and the drive trips
• Wrong motor parameters: incorrect nameplate data or no autotuning makes the drive push too much magnetising current
• Damaged motor or cable: insulation breakdown, winding short or cable leakage pulls high current
• Mechanical jam: seized bearing, blocked pump or jammed conveyor makes the motor demand more torque than available
• Wrong V/f curve or low speed stall: the voltage/frequency pattern does not match the load at the operating point

Step-by-Step Diagnosis

Preventative Settings

• Autotune the motor: always run the drive's motor identification when commissioning, especially with a new or changed motor
• Set acceleration/ deceleration ramps to the load: start around the load's natural ramp and adjust down only if the process needs it
• Use current-limitation and torque-limitation functions: they prevent the current from reaching the trip level while keeping the drive running where possible
• Match the V/f curve or use vector control for loads with difficult low-speed torque – see our load-type selection guide
• Check motor data against the nameplate: wrong rated current is one of the most common root causes

Frequently Asked Questions

Does an OC trip damage the VFD? The protection is designed to protect the drive; one trip rarely causes damage. Repeated trips under load stress the power stage, so find and fix the cause rather than simply resetting. See our overvoltage troubleshooting guide for the related DC-bus fault.

My drive trips at the same speed every time – why? A repeatable trip point usually points to a mechanical resonance or a V/f curve mismatch at that speed, or a winding fault that appears at that load point. Measure the current at that speed and compare with the drive rating – our sizing guide explains the ratings.

If OC trips persist after these checks, contact our service team with the fault code and trip log – see our VFD FAQs and the low-voltage VFD range.