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How Contactors Work

Apr 24, 2018

The contactor is the most commonly used and most important control device in industrial control. The electromagnetic contactor uses the electromagnet principle to open and close the circuit.


Working principle

As shown in Fig. 1, the principle of closing the main circuit is as follows: power supply is turned on → coil is energized → magnetic flux is generated in the iron core → electromagnetic attraction force is generated → electromagnetic force is overcome against spring force → armature is attracted → contact mechanism is actuated → main contact is closed → The main circuit is switched on.

Disconnect the principle of the main circuit: the coil is de-energized or too low → the electromagnetic force is less than the spring force → the armature is released → the contact mechanism is reset → the main circuit is disconnected.

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Fig. 1 Principle of contactor


Structure and composition

The contactor is composed of electromagnetic mechanism, contact system, arc extinguishing system and other components. The composition and function are shown in Table 1.


Table 1 The composition of the contactor

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Classification

According to the supply current, the contactor can be divided into AC contactor and DC contactor.

According to magnetic characteristics, contactors can be divided into electromagnetic contactors and permanent magnet contactors;

According to voltage level, contactor can be divided into high voltage contactor and low voltage contactor;

According to the application, the contactor can be divided into a contactor for a motor, a contactor for a capacitor, and a contactor for lighting.


Effect

The contactor is a control electrical appliance, widely used in local, remote control of the motor and other equipment, can be frequently operated, is the most basic and most important control electrical appliances in industrial control.


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