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.

There are three kinds of tripping modes: thermal tripping, electromagnetic tripping and multiple tripping. When a general overload occurs to the line, although the overload current cannot make the electromagnetic release act, it can make the thermal element generate a certain amount of heat, make the bimetallic sheet bend upward under the heat, push the lever to disconnect the hook from the latch, disconnect the main contact, and cut off the power supply. When the short circuit or serious overload current occurs in the line, the short circuit current exceeds the instantaneous tripping setting current value, and the electromagnetic release generates enough suction to absorb the armature and impact the lever, so that the hook rotates upward around the rotating shaft base and disengages from the latch, and the latch breaks the three main contacts under the action of the reaction spring, cutting off the power supply.