The air switch used on wheelchair lifter and residential freight elevator is a switch that will automatically disconnect as long as the current in the circuit exceeds the rated current. Air switch is a very important electrical appliance in low-voltage power distribution network and electric drive system. It integrates control and multiple protection functions. In addition to completing contact and breaking circuits, it can also protect short circuits, severe overloads and under voltages that occur in circuits or electrical equipment, and can also be used to start motors infrequently.
There are 3 types of tripping methods: thermal tripping, electromagnetic tripping and double tripping.When a general overload occurs in the circuit, although the overload current cannot cause the electromagnetic release to operate, it can cause the thermal element to generate a certain amount of heat, which will cause the bimetallic sheet to be heated upwards, push the lever to disengage the hook and the lock, and bring the main contact The head is disconnected and the power supply is cut off. 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 sufficient 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.
The tripping mechanism of the switch is a set of linkage devices. When the main contact is closed by the operating mechanism, it is locked in the closed position by the lock hook. If there is a failure in the circuit, the relevant trip unit will act to release the lock hook in the trip mechanism, so the main contact is quickly disconnected under the action of the release spring. According to the different protection functions, the tripping device can be divided into the over current tripping device and the voltage loss tripping device. Air switches are widely used in strong electric circuits, such as lifting platform Lift Tables, Aerial work platform, cargo elevators, and household elevators.
