Troubleshooting Delta VFD "oc" Faults
Delta VFDs often display the "oc" (overcurrent) fault code during acceleration (ocA), deceleration (ocd), or constant speed (ocn). This guide explains how to troubleshoot these faults at the component level.
1. oc during Acceleration (ocA)
Cause: Short circuit in the motor, high load friction, or a damaged output stage. Action: Disconnect the motor and test the drive. If the fault persists, inspect the IGBT inverter stage and replace damaged switching components.
2. oc during Deceleration (ocd)
Cause: Regenerative voltage feedback from the motor. Action: Increase the deceleration time or check the dynamic braking chopper and resistor.
3. oc at Constant Speed (ocn)
Cause: Sudden load changes or a fault in the VFD's current sensing circuit. Action: Inspect the Hall-effect current sensors on the output phase lines and replace them if their feedback voltage is drifting.