Cause : Supply phase loss comes when the PH.Lo trip indicates that the drive has detected an input phase loss or large supply imbalance. The drive will attempt to stop the motor before this trip is initiated. If the motor cannot be stopped in 10 seconds the trip occurs immediately.

1. The PH.Lo trip works by monitoring the ripple voltage on the DC bus of the drive, if the DC bus ripple exceeds the threshold, the drive will trip on PH.Lo.
2. Potential causes of the DC bus ripple are input phase loss, Large supply impedance and severe output current instability.
3. Check the AC supply voltage balance and level at full load.
4. Check the DC bus ripple level with an isolated oscilloscope.
5. Check the output current stability.
6. Check for mechanical resonance with the load.
7. Reduce the duty cycle.
8. Reduce the motor load.
9. Disable the phase loss detection, set Pr 06.047 to 2.