The AC contactor uses the main contact to control the circuit, and the auxiliary contact to conduct the control loop.
The main contact is generally a normally open contact, and the auxiliary contact often has two pairs of normally open contacts and a normally closed contact. Small contactors are often used as intermediate relays to cooperate with the main circuit.
The contacts of the AC contactor are made of silver-tungsten alloy, which has good electrical conductivity and high temperature ablation resistance.
The power of the AC contactor's action comes from the magnetic field generated by the AC passing through a coil with an iron core. The electromagnet core is composed of two "hill" shaped young silicon steel sheets. One of the fixed iron cores is covered with a coil. The working voltage can be varied. select. In order to stabilize the magnetic force, a short-circuit ring is added to the suction surface of the iron core. After the AC contactor loses power, it relies on the spring to reset.
The other half is the movable iron core, the structure is the same as the fixed iron core, used to drive the main contact and auxiliary contact to close and open.
The contactor above 20A is equipped with an arc extinguishing cover, which uses the electromagnetic force generated when the circuit is disconnected to quickly break the arc and protect the contact.
The contactor can be operated at a high frequency. When used as a power switch on and off control, the maximum operating frequency can reach 1,200 times per hour.
The service life of the contactor is very high, the mechanical life is usually several million to 10 million times, and the electrical life is generally hundreds of thousands to several million times.