Contactor working principle

Guide: A contactor is an automatic control device that uses electromagnetic force to open or close its main contacts, allowing it to frequently switch the main circuit with a load. But how exactly does it work? This article will take you through the entire process and explain the working principle of contactors in detail.

First, the Working Principle of the Contactor – An Introduction

A contactor is an electrical device used in industrial power systems. It works by passing current through a coil, which generates a magnetic field. This magnetic field pulls the contacts together, allowing the flow of electricity to the connected load. Contactors are widely used in electrical engineering because they can quickly disconnect the main circuit and handle frequent switching of high-current devices.

Second, the Working Principle of the Contactor – Classification

Contactors can be classified into DC contactors and AC contactors based on the type of current they handle. DC contactors typically use a modular design and are built with minimal components to meet specific customer needs, such as the number and type of contacts required. They operate at higher voltages and use a horizontal magnetic field for arc suppression, making them ideal for applications like program-controlled power supplies, uninterruptible power systems, and construction equipment.

On the other hand, contactors can also be divided into electromagnetic contactors and permanent magnet contactors based on their operating mechanism. Permanent magnet contactors use the repulsion between like magnetic poles and are powered by a permanent magnet instead of an electromagnet. These are known for their low power consumption and are commonly found in modern industrial applications. Examples include models like CJ20J, NSFC1, and NSFC2.

Third, the Working Principle of the Contactor – Structure

An AC contactor is composed of four main parts: the electromagnetic system, the contact system, the arc suppression device, and various accessories. The electromagnetic system includes the attracting coil, a stationary iron core, and a moving iron core. The contact system is connected to the moving iron core and consists of three main contacts along with one set of normally open and normally closed auxiliary contacts. The arc suppression device helps quickly cut off the current to prevent damage to the main contacts, especially in large-capacity contactors. In addition, there are insulating casings, springs, transmission mechanisms, and wiring terminals that make up the overall structure.

Fourth, the Working Principle of the Contactor

When the coil is energized, the static iron core generates an electromagnetic attraction, pulling the moving iron core towards it. This movement causes the three movable contacts in the contact system to close, turning on the main circuit. At the same time, the auxiliary normally closed contact opens, while the auxiliary normally open contact closes, completing the circuit and powering the connected device.

When the coil is de-energized, the magnetic field disappears, and the spring pushes the moving iron core away from the static iron core. This action opens the main contacts and closes the auxiliary normally closed contact, while the auxiliary normally open contact opens, effectively cutting off the power supply.

Contactor Working Principle