Contactors are divided into AC contactors and DC contactors, and are widely used in the fields of electric power, distribution, and electrical applications. Contactors are electrical devices used in industrial circuits. They generate a magnetic field by passing current through a coil, which in turn closes the contacts to control the load.

The working principle of a contactor is as follows: When the coil of the contactor is energized, it generates a magnetic field that attracts the movable iron core, causing it to connect with the stationary iron core. As a result, the normally closed contacts of the AC contactor open, and the normally open contacts close. The normally closed and normally open contacts are interlocked.

When the coil is de-energized, the magnetic field disappears, and the movable iron core returns to its original position under the action of a release spring. The contacts also return to their initial state, with the normally open contacts opening and the normally closed contacts closing. The working principle of a DC contactor is similar to that of a temperature switch.

Normally closed switches have various structural types and can be used as stop switches and push-button switches. Common types include ordinary push-button type, mushroom head type, self-locking type, self-resetting type, rotary handle type, indicator light type, symbol light type, and key type. These push-button switches come in single-button, double-button, triple-button, and different combination forms, usually adopting a modular structure.

Push-button switches consist of button caps, reset springs, bridge contacts, and housings, usually in a composite form. They typically include a pair of normally closed contacts and normally open contacts. Some products can increase the number of contacts by connecting multiple components in series. There is also a type of self-holding button that can automatically maintain a closed state when pressed and can only be opened when power is cut off.