The trip modes of the air circuit breaker include thermal trip, electromagnetic trip and multiple trip.

1、When the general overload occurs in the line, although the overload current can not make the electromagnetic release device operate, it can make the thermal element produce a certain amount of heat, and cause the bimetal sheet to bend upward when heated, push the lever to make the hook and the lock off, break the main contact, and cut off the power supply.

2、When there is a short circuit or serious overload current in the line, the short circuit current exceeds the instantaneous tripping setting current value, and the electromagnetic tripping device generates a large enough suction force, impinges the armature suction combination on the lever, and makes the hitch turn upward around the rotating shaft seat and the lock is released. The lock breaks the three pairs of main contacts under the action of the reaction spring to cut off the power supply.

The tripping mechanism of the switch is a connecting rod device. When the main contact is closed by the operating mechanism, it is locked in the closing position by the locking hook. If a fault occurs in the circuit, the relevant trip device will act to disengage the hook in the trip mechanism, so that the main contact is quickly broken under the action of the release spring. According to the different protective effects, the release device can be divided into over current release device and no voltage release device.