When testing whether the power supply protector is normal, professional personnel should be invited to use the leakage phase detector to test. If the power supply protector is in the normal protection state, the power supply protector of each circuit will trip separately, and the leakage protector will also trip together. If the power supply protector is in an abnormal state, only the main switch trips, the separate power supply protector does not trip, and the leakage protector does not trip.

Under normal conditions, the armature of the overcurrent release is released; In case of serious overload or short circuit fault, the coil connected in series with the main circuit will generate strong electromagnetic attraction to draw the armature down and lift the locking hook, making the main contact disconnected.