What is the structure, parameters and principle of AC contactor?

1、First, the basic structure and components of the AC contactor

AC contactor is mainly composed of electromagnetic system, contact system, arc extinguishing system, auxiliary components and other parts.
Electromagnetic system contains electromagnetic coil and iron core, when the electromagnetic coil is energized, it will generate a magnetic field to attract the iron core action. Contact system has the main contact and auxiliary contact, the main contact is used to connect and disconnect the main circuit, bear a large current; auxiliary contact is mainly used for signaling in the control circuit, etc., the current is smaller. Arc extinguishing system is used to extinguish the arc generated when the contact breaks the circuit, to prevent damage to the contact arc and avoid causing electrical accidents. Auxiliary components including shell, spring, terminals, etc., the shell plays a protective role, the spring for the action of the contact to provide reset force, the terminals to facilitate the electrical connection.

2、Definition of rated voltage and rated current of AC contactor

The rated voltage of the AC contactor is the voltage value that it can work normally and the insulation is not damaged. It is determined according to the insulation material and design structure of the contactor, usually including the rated working voltage of the main contact and the rated voltage of the electromagnetic coil. For example, the rated working voltage of main contact may have different specifications such as 220V, 380V, etc., and the rated voltage of solenoid coil commonly has 220V, 380V, and some control circuits commonly used in lower voltage such as 110V, 24V, etc. The rated current refers to the value of AC contactor insulation material and design structure. Rated current refers to the maximum current allowed to pass through the main contacts of the AC contactor that can work normally for a long time under the specified conditions. This parameter depends on the contact material, contact area, heat dissipation conditions and other factors, such as the rated current of 10A, 20A, 40A and other different levels, in the selection of AC contactors, according to the size of the load current of the control circuit to determine the appropriate rated current to ensure that the contactor can operate reliably and will not be damaged due to overload.

3、The working principle of AC contactor

The working principle of AC contactor is similar to an electromagnetic switch. When the electromagnetic coil is connected to a suitable power source (e.g., rated alternating current), a current passes through the coil, which generates a magnetic field. This magnetic field magnetizes the iron core and generates electromagnetic suction, which overcomes the reaction force of the spring and attracts the movable iron core (armature) into action. When the movable iron core and the static iron core are absorbed, the main contact connected to it is driven to close, connecting the main circuit, and the load starts to work. When the electromagnetic coil is disconnected, the magnetic field disappears, the electromagnetic suction of the iron core also disappears, under the action of the spring, the dynamic iron core reset, the main contact is disconnected, cut off the main circuit, the load stops working. Throughout the process, the electromagnetic system controls the action of the contact system to realize the on-off control of the circuit, like an automatic electromagnetic control of the switch, according to the control signal (electromagnetic coil is energized and de-energized) to determine the working state of the circuit.