Cause : GFF occurs before run comes when the ground short circuit detected when the output wiring detection is performed before the drive runs. This means the drive identifies a potential issue with grounding during its initial power-on checks.

The error code b4GFF on your Delta MS300 drive indicates a ground fault detected before the drive even starts (b4 stands for "before"). This means the drive identifies a potential issue with grounding during its initial power-on checks and prevents operation to ensure safety.

1. Check if the motor’s internal wiring and the UVW wiring of the drive output terminal are correct.
2. Check the motor cable and remove causes of the short circuits, or replace the cable before turning on the power.
3. Check the motor insulation value with megger.
4. Replace the motor if the insulation is poor.