What is Magnetic Contactor and How It's works

We know that for power wiring / 3 phase motor wiring we use mostly the magnetic contactor or motor starter. In this post, we will study the magnetic contactor importance, working/function, and its uses in electrical technology. I also share posts about the M contactor wiring diagram but this post especially for the function and working of the 3 phase contactor or motor starter.

What is a Magnetic Contactor?

We can also say that a contactor is a type of electrical relay which we use to power electric motor to start or stop. The contactor makes it easy to control 3 phase induction motors. We know that 3 phase motor required three phase supply to run, 3 phase supply is two dangerous which we can not handle with a circuit breaker for an induction motor. The contactor makes it easy to handle the 3 phase motor control. The parts of the magnetic contactor are coil, iron core, 3 contact points, and NC, NO points.

magnetic contactor

How a Magnetic contactor Works

The function of a contactor or motor starter is simple, when the AC supply goes to the contactor coil, the coil makes a strong magnetic field and the field pulls the iron core to the coil and makes electrical contacts.

What are NC, NO in Contactor
The NC means the Normally close electric circuit or we can say it is normally close contact and NO means normally open contacts. In the normal state when the contactor coil does not energize the NC point is the normal close state and when the coil energizes these NC contacts create an open circuit between one another after coil de-energized NC contacts make a close circuit.
Same the NO contacts change on coil energizing to the close circuit.

Advantages of Contactor

There are many advantages of 3 phase contactor but some are very important which are below.
You can control power motors easily by pushing a small button.
You can ON/OFF electrical 3 phase motor in a small time.
You can save himself from electric shock in 3 phase motor starting.

Sikandar Haidar

Electricalonline4u.com is a hub of electrical and electronics tutorials and easy diagrams.


  1. Thanks a lot for this easy read.

  2. Sir thank you
    Sir i want to make wireless sensor network based drip irrigation system. Soil moisture sensors will be installed in the field. In system motor size is 7.5 hp and 440 volt water pump. Sir how i can automate this water pump by Contractors or Relay


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