The phase reversal protection function PREVPTOC is used to detect the reversed connection of the phases to a three-phase motor by monitoring the negative phase sequence current I 2 of the motor.
PREVPTOC starts and operates when I 2 exceeds the set limit. PREVPTOC operates on definite time ( DT) characteristics. PREVPTOC is based on the calculated I 2, and the function detects too high I 2 values during the motor start-up. The excessive I 2 values are caused by incorrectly connected phases, which in turn makes the motor rotate in the opposite direction.
The function contains a blocking functionality. It is possible to block function outputs, timer or the function itself.