Ac Contactor working principle and structure

General idea about Ac Contactor

AC contactor is a kind of electromagnetic type contactor with main contact normally open, three phase, using air as arcing mechanism electromagnetic type contactor.

Its components include: coil, short circuit ring, static core, moving contact, static contact, auxiliary normally open contact, auxiliary normally closed contact, pressure spring, reaction spring, buffer spring and so on. Popular contactors in our current market are   CJX2, 3TF, CJT1, CJ20 contactor etc.              .

The main components of the AC contactor are shown as below:

AC magnetic contactor main struacture

Electromagnetic system: coil, static core and moving core (also known as armature)

Contact system: Includes main contacts and auxiliary contacts. The main contact allows the main circuit to be actuated by a large current which normally connect or disconnect the main circuit. The maximum current which allowed by the main contacts (ie, rated current) is usually one of the main technical parameters of the contactor. The auxiliary contacts are only allowed to pass through smaller currents so that they are generally connected to the control circuit.

Main contacts of ac contactor are generally open contact, auxiliary contacts (normally open contacts and normally closed contacts). Contactor with smaller rated current has four auxiliary contacts; rated current larger, but contactor with bigger rated current has six contacts.

The so-called normally open, normally closed refers to the sate of contacts before electromagnetic system is energized and activated; that is, normally open contact means that the dynamic and static contact is in the open state before the coil is energized; when the coil is powered, it will be closed so that the normally Open contact also can be called as making contact. However, normally closed contact means that the dynamic and static contact is closed before the coil is energized, and wehn the coil is powered, it opens so that the normally closed contact is also known as breaking contact.

The use of arc extinguishing device is to quickly cut off the arc when the main contact is broken.  It can be seen as a large current if not quickly cut off, will occur the main contact singeing, fusing and so on. Therefore, AC contactors are generally equipped with arc extinguishing device. For the AC contactor with larger capacity, extinguishing arcing grid will usually be used.

Working principle of AC contactor

Working principle of AC contactor is as shown in the picture. When the coil is energized, the core is magnetized to attract the armature to move down to make the normally closed contact open and normally open contact closed. When the coil is powered off, the electromagnetism disappears, the armature returns to its original position and contact returns to its original state under the action of the reaction spring.

AC magnetic contactor working principle

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