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.

The tripping mechanism of the switch is a set of connecting rod devices. When the main contact is closed through the operating mechanism, it will be locked in the closing position by the locking hook. If there is a fault in the circuit, the relevant release will act to release the locking hook in the release mechanism, and the main contact will quickly break under the action of the release spring. According to the different protection functions, the release can be divided into over-current release and voltage-loss release.