VFD & Motor Control3 min read
What to record when a VFD shows an overcurrent fault
Capture the trip timing, alarm code, and motor nameplate data before requesting variable frequency drive diagnostics.
1. Note when the overcurrent alarm occurs
An overcurrent trip (often OC1, OC2, or OC3 depending on the drive brand) gives different diagnostic clues depending on when it happens:
- Trip during acceleration: rapid ramp-up time, mechanical pump binding, or shorted motor winding
- Trip during constant speed: sudden mechanical load spike, low supply voltage, or failing current sensor
- Trip during deceleration: regenerative DC-bus overvoltage or missing braking resistor
2. Nameplate details to photograph
Before resetting the drive repeatedly—which can stress the IGBT bridge—photograph the VFD nameplate, the motor rating plate, and the exact keypad alarm code, and note whether the motor turns freely when disconnected.