1. Overload protection When the motor runs over the rated current for a long time under the overloaded fault, it will cause the motor to overheat, reduce the insulation and burn down. The protector calculates the thermal capacity of the motor according to the heating characteristics of the motor. The characteristics of different tripping levels corresponding to the protection of the motor by simulating the heating characteristics of the motor and the overload protection. 2 . Underload protection When the load of the motor is the pump type load , the motor no – load or under – load transfer is harmful , the protector provides under – load protection , and when the percentage of the average current of the three – phase and the rated current is lower than the set value , the protector shall operate within the action ( delay ) setting time or alarm within the alarm time . 3, blocking / blocking protection When the motor is starting or running, if the electric timing shaft is jammed be...