Cause : W-phase over-current before run comes when W-phase short circuit detected when the output wiring detection is performed before the drive runs.

An "coc" fault in Delta MS300 drive indicates "over-current situation in the W phase before the motor even starts running". This means there's a short circuit or ground fault detected in the W phase output of the drive.

1. Check if the motor’s internal wiring and the UVW wiring of the drive output terminal are correct.
2. Check the motor cable.
3. The boc occurs due to the short circuit or ground fault at the output side of the drive.
4. Check for possible short circuits between terminals with the electric meter: B1 corresponds to U, V and W; DC- corresponds to U, V and W.