The invention provides a protecting device used for the power load, comprising a breaker of a tripping unit; when the selected time-related function of the current breaker reaches the tripping value, the tripping unit opens the breaker; when the selected time-related function reaches the value, the tripping unit generates the pre-tripping output; the selected tripping value is lower than the tripping value; and a contactor electrically connected to the breaker and the load comprises a separated contactor, having the closing state of the contactor of the contactor; the currency of the contactor is in the opening state and the device with the open state outputting the pre-tripping device operated to the contactor. The invention eliminates the needs of cutting the relay via the device and provides the motor protection.