Analysis of the Selection and Working Principle of AC Contactor

(1) Continuously operated equipment. The contactor is calculated as 67-75%. That is, the 100A AC contactor can only control the equipment whose maximum rated current is 67-75A or less.

(2) Intermittently operated equipment. 80% of the contactor is the 100A AC contactor, which can only control the equipment whose maximum rated current is 80A or less.

(3) Equipment for repeated short-term work. The contactor counts as 116-120%. The 100A AC contactor can only control equipment with a maximum rated current of 116-120A or less.

AC contactors are widely used as power breaking and control circuits. It uses the main contact to open and close the circuit and the auxiliary contact to execute the control command. The main contact is generally only a normally open contact, while the auxiliary contact often has two pairs of contacts with normally open and normally closed functions. The small contactor is often used as an intermediate relay in conjunction with the main circuit. The contact of the AC contactor is made of silver-tungsten alloy and has good electrical conductivity and high temperature ablation resistance.

AC contactors are mainly composed of four parts:

(1) Electromagnetic systems, including attracting coils, moving iron cores and static iron cores;

(2) Contact system, including three main contacts and two normally open and two normally closed auxiliary contacts, which are linked together with the moving iron core;

(3) arc extinguishing devices, AC contactors with larger capacity generally have arc extinguishing devices so that the arc can be quickly cut off and the main contacts can be prevented from being burned out;

(4) Insulation shells and accessories, various springs, transmission mechanisms, short-circuit rings, terminal posts, etc.

working principle:

When the coil is energized, the static iron core generates an electromagnetic suction force, and the moving iron core is attracted. Since the contact system is linked with the moving iron core, the moving iron core drives three moving contact pieces to operate at the same time, and the contact is closed, thus connecting power supply. When the coil is de-energized, the suction force disappears, and the moving part of the moving iron core separates due to the reaction force of the spring, so that the main contact is disconnected and the power is cut off.