AC contactor is mainly composed of four parts: (1) electromagnetic system, including attracting coil, moving core and the fixed iron core; (2) contact system, including three sets of main contacts and one or two normally open, normally closed auxiliary contacts, which are linked to the movable core and linkage to each other; and (3) interrupter device, generally larger capacity AC contactor has interrupter device to quickly cut off the Arc, burned from the main contact ; (4) insulated housings and accessories, all kinds of springs, transmission, short ring, terminal and so on. When the coil is energized, the static core generates electromagnetic force, the movable core pull, since the contact system is linked with the moving core, moving core and therefore drive three movable contacts operated simultaneously, the main contact is closed, and the main auxiliary contacts mechanically coupled to the normally closed contacts open, auxiliary normally open contact closure, thereby turning on the power. When the coil power, suction disappear, moving core linkage relies in part on the reaction force of the spring separating the main contacts to open, and the auxiliary main contacts mechanically coupled to the normally closed contacts closed, auxiliary normally open contact disconnect , thereby cutting off the power supply.