How Does a Magnetic Contactor Work?

By Staff WriterLast Updated Apr 3, 2020 1:41:21 PM ET
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A magnetic contactor works by creating a connection between the motor and the electromagnet. When the start button is pressed in a magnetic starter, an electromagnet gets energized and the contactor gets engaged. As a result, the current runs to the motor.


A magnetic contactor is part of an electromagnetic-operated switch that starts and stops a large-load electric motor through a control circuit that connects contact devices to the magnetic motor starter coil. The magnetic contactor is usually paired with an overload relay in a magnetic starter to flick the switch when the motor load exceeds its capacity.

A magnetic contactor may be present in a magnetic starter as either stationary or moving, together with a solenoid coil, pressure springs, an electromagnet that is kept in place, magnetic shading coils and a mobile armature.

If the motor has not been started yet, the magnetic starter does not receive current. As soon as the start button is activated, the electromagnet is powered up. The switch then engages the contactor and directs the current to the motor. When the stop button is pressed, the circuit is broken, which removes the energy from the electromagnet and current to the motor.

The electromagnet automatically disengages the contactor when the motor power fails. This is possible through the use of momentary switches to call the functions on and off. A magnetic contactor coupled with an electromagnet is similar to ordinary latching mechanisms such as a light switch, although the latter does not disengage when power to the motor fails.