The working principle and application of AC contactor

AC contactor is a kind of intermediate control element, which is composed of moving and static main contacts, arc extinguishing cover, moving and static iron cores, auxiliary contacts and bracket shell. It adopts three arc extinguishing methods of double-fracture point-action arc extinguishing, longitudinal slit arc extinguishing and grid plate arc extinguishing. Its advantage is that the circuit can be frequently turned on and off, and the large current can be controlled with a small current. Working with the thermal relay can also play a certain role in overload protection for the load equipment. General contactors are equipped with arc extinguishing devices as long as the capacity is above 10A.

working principle

When the contactor coil is energized, the coil current will generate a magnetic field. The generated magnetic field causes the static iron core electromagnetic attraction to attract the moving iron core and drive the AC contactor point to act. The normally closed contact is disconnected and the normally open contact is closed. It is linked. When the coil is de-energized, the electromagnetic attraction force disappears, and the armature is released under the action of the release spring to restore the contact, the normally open contact is disconnected, and the normally closed contact is closed.

Application

AC contactors are widely used in power breaking and control circuits. The AC contactor uses the main contact to open and close the circuit, and the auxiliary contact to execute the control command.
The main contact generally only has a normally open contact, while the auxiliary contacts often have two pairs of contacts with normally open and normally closed functions. 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 action power of the AC contactor comes from an AC electromagnet. The electromagnet is made up of two thin silicon steel sheets, one of which is fixed and a coil is placed on it. There are a variety of operating voltages to choose from. 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 opening and closing of the main contact and the auxiliary contact. The contactor above 20 amperes is equipped with an arc extinguishing cover, which uses the electromagnetic force generated when the circuit is disconnected to quickly break the arc to protect the contact.