What is Contactor and why used?


Friends, if you are connected with electrical, then you must have heard the name of the contactor, but if any question related to the contactor is asked in the interview or exam, then some people are not able to answer it correctly.

So in today’s post, important questions related to the contactor such as: why contactor used, what is the difference between mcb and contactor, what things should be kept in mind while installing a contactor?

you will understand all these questions very well. Apart from this, we will also understand how the contactor works. So that if in future any question related to contactor comes in interview or exam, you can quickly answer it without any confusion.

What is Contactor?

Friends, you must have seen the switch installed in the house. These switches are used to turn on/off. In the same way, the contactor is also used as a switch to turn on/off electrical equipment.


Now the question will come: What is the difference between a standard switch and a contactor?

What is difference between Normal Switch and Contactor?

Friends, if we talk about the normal switch and contactor, some people will say that the normal switch is used to connect the low rating equipment, and the contactor is used for high power or higher rating equipment. Friends, this is true, but there is the main difference between a normal switch and a contactor. Which completely separates these two.


If we tell you very simply, you can say that normal switches are mechanically operated, but our contactors are electrically operated. Now the question is, what is the difference between electrically operated and mechanically operated switch? So let’s understand the answer of this question.

What is Difference in Electrical and Mechanical Operated Switch?

Friends, the biggest difference between electrical operated and mechanical operated switch is that, whenever we want to operate something, in mechanical switch, we have to go near that switch and press the button. But if we talk about electrical switch, then we can operate it with electrical signal without going near contactor.contactor-control-panel

If we want to turn on the supply from the contactor, then we do not need to go near contactor and press the button, we can also turn the supply on/off by giving an electrical signal from a distance or by applying a push button.

Friends, if you do not know how the contactor is turned on, then let’s understand how the supply is turned on/off from the contactor.

How to Operate Contactor?

Friends, it is quite easy to operate the contactor. You have to find the A1 A2 terminal on your contactor. There are A1 A2 terminals on all the contacts. This A1 A2 terminal becomes on the side of some contactors, A1 terminal of some contacts on one side and the A2 terminal on the other side. So A1 A2 terminal may be somewhere but every contactor must have both terminals.


Now you have to look carefully near A1 A2 terminal, then something like in above image will be written there.

So friends, the 220 written here means that the coil inside our contactor will operate on 220 voltage. Meaning as we connect the A1 A2 terminal of this contactor to the 220 voltage of phase neutral, then our contactor will be ON. When the contactor is turned on, the supply will be turned on.

Note: The 220 volts written in the middle of our A1 A2 terminal does not mean that if we supply voltage more than 220 volts, then the contactor will be damaged. Friends, this 220 volt means how much supply we need to turn on the contactor.
Friends, if we talk about the range of this contactor, then you can see the table on its side. The current and voltage written in it, is the range of our contactor. That is, if we connect load more then it’s rating then, it can be damage.
So friends, this is the difference between a contactor and a normal switch. Now let’s talk about what things should be kept in mind while installing the contactor?

What things to Keep in Mind While Installing Contactor?

Friends, whenever you put a contactor, you always have to keep in mind that the contactor is a kind of switch. The contactor does not provide any protection. So we should always connect circuit breaker with it. Sometimes we put OLR along with the conductor, which we call overload relay.contactor-with-OLR-relay

If you are not installing OLR then you must install at least MCB. We must install some breaker to protect the our load.

Friends, in the last, let’s discuss summery of our entire post. What are the benefits to be seen separately by applying the contactor.

Friends, our contactor is a kind of switch which we can turn on/off with the help of push button. Instead of a push button, you can also operate the contactor electrically. Meaning that we can operate it without going to near contactor. As if there is a motor installed in your farm, then you can turn it on/off from your mobile at home.
Apart from this, we can also set a timer along with the contactor, as if you want your motor to turn on after 10 minutes and turn off after 5 minutes, then you can do all this with the help of contactor. We cannot do all these things with the normal switch. So because of such freedom, we use contactor.

We hope that you got all the information related to the contactor. If any question left then you can comment out below or you can send question to us on Instagram Electrical Dost.”

If you like to see video of electrical then you can visit our channel Electrical Dost.” 

Thank You 🙂

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Aayush Sharma is an Assistant Engineer in a Semi-Government Company and Owner of "Engineering Dost" and the Electrical Dost YouTube Channel. He Provides you Engineering inquiry and support of engineering market facts with Practical experience.



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