The phase unbalance feature will protect motors of any size against:
Excessive temperature rise due to unbalanced supplies ( e.g. a 10% unbalanced supply can increase the temperature rise by 150%)
The regenerated voltage generated during a single phase failure when running at low load.
Principle of Operation
The protector comprises monitoring circuits for voltage phase reversal and phase unbalance. Outputs from these circuits are fed to a comparator which changes state under fault conditions.
When the comparator trips, the output relay will de-energise after a preset time delay & the red LED will then no longer be lit.
The relay and LED will automatically energise again when all the supply parameters have returned to safe and acceptable limits.