When the line is short-circuited or severely overloaded, the short-circuit current exceeds the instantaneous tripping setting current value, and the electromagnetic tripping device generates enough suction force to attract the armature and hit the lever, so that the hook rotates upwards around the shaft seat and the lock is released , The lock breaks the three main contacts under the action of the reaction spring to cut off the power supply.

When a general overload occurs in the circuit, although the overload current cannot make the electromagnetic release actuate, it can cause the thermal element to generate a certain amount of heat, prompting the bimetallic sheet to be heated upwards, pushing the lever to disengage the hook and the lock, and then the main contact The head is disconnected and the power supply is cut off.

Because there are many insulation methods, there are oil switches, vacuum switches and other inert gas (sulfur hexafluoride gas) switches. An air switch is a switch that uses air to extinguish the arc, so it is called an air switch. Air is used to extinguish the arc generated during the switching process. So it is called an air switch.