When the contactor coil is not powered up, the auxiliary contacts of the contactor in the natural state have no conducting contacts, which are usually expressed as NO, and the normally open contacts are disconnected, while the normally closed contacts are the contacts in the conducting state in the natural state, which are usually expressed as NC, and the normally closed contacts are connected.

Contactors are divided into AC contactor (voltage AC) and DC contactor (voltage DC) according to the main contact connection circuit. According to the operating mechanism, it can be divided into electromagnetic contactor and permanent magnet contactor. Contactors are mainly used in electric power, distribution and power applications to effectively protect the mechanical and electrical life of electrical appliances.