Cause : Supply phase loss comes when the drive has detected an input phase loss or large supply imbalance. Phase loss can be detected directly from the supply where the drive has a thyristor base charge system.

In all sizes of drive phase loss is also detected by monitoring the ripple in the DC bus voltage in which case the drive attempts to stop the drive before tripping unless bit 2 of Action On Trip Detection (10.037) is set to one.

1. Check the AC supply voltage balance and level at full load.
2. Check the DC bus ripple level with an isolated oscilloscope.
3. Check the output current stability.
4. Check for mechanical resonance with the load.
5. Reduce the duty cycle.
6. Reduce the motor load.
7. Disable the phase loss detection, set Pr 06.047 to 2.