Why is the display showing a PHbd fault code on the ATS22 soft starter?


28 September 2021

PHbd fault on the ATS22 soft starter.

Product Line:
Altistart ATS22


PHbd is a phase imbalance fault.

The ATS22 monitors the current draw through each phase. The ATS22 faults PHbd when the current unbalance exceeds the unbalance threshold and time delay.  Unbalance is calculated (Imax - Imin) / Imax.  

Troubleshooting steps:

1. Check line voltage (phase-phase).  An unbalanced voltage results in imbalanced current.
2. In the PRO Menu, check the following parameters:
Ubd - Unbalance threshold.  A larger value is more tolerant of current imbalance. This setting can be set to OFF, disabling the feature.
Ubt - Unbalance time delay.  Time that the imbalance needs to be maintained before the ATS22 will trip.
3.  With Ubd = OFF, run the motor and check the current draw on each phase.  If the current is not balanced and the voltage is balanced, problem is related to the motor. If both are balanced, then the problem could be related to the soft start.