Is a line isolation contactor or shunt trip circuit breaker needed with SquareD soft starters?
Since the solid-state switches may be incapable of completely blocking the motor power should a fault occur, auxiliary isolation on the line side of the controller is required. Use either a circuit breaker equipped with a shunt trip coil or an electromagnetic contactor. Connect the isolation device to the fault relay of the controller so that it opens the controller power circuit in the event of a controller fault. The isolation device must be capable of interrupting motor locked rotor current.