It is a circuit breaker which has higher instantaneous tripping current value in order to prevent unwanted tripping by magnetizing inrush current of a transformer ,compared with general circuit breakers. You can use it for a circuit having large inrush current such as a circuit at primary side of a transformer. You must install a switch for switching since the making lifetime for primary side circuit of transformer of a circuit breaker will significantly decrease due to the effect of magnetizing inrush current.