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Insight - How MCB works

Written By: 

Arpit Jain
The following image illustrates the tripping mechanism of the MCB. The circuit breaker contacts and the position of the knob can easily be seen in both, ON and OFF, state. In the ON state the moveable contact touches the fixed contact as shown in the image.

Tripping mechanism of MCB

The path of the current in the ON state is shown in the image below. The live wire is screwed at the input terminal. From the input terminal the current flows to the fixed contact which is touching the input terminal. The current then moves to the moving contact (since in the ON state it is touching the fixed contact). The moving contact is connected to the electromagnetic coil of the solenoid by means of a thick wire. The current from the moving contacts enters the electromagnetic coil. The current from the coil goes to the bimetallic strip by means of another thick wire and finally to the output terminal where it is collected by the neutral wire of the line.

Current Flow




I likeD it..I had seen it many times at my home but nver tried to know how it works..thanks to engineersgarage ..evrone shud watch its intresting
explanation is strong. thanks. regards, raja giri


gr8 work.. arc quenching explained nicely. now I know what arc chutes are for.

wow, very nice.




mcb is a best of electrical component


nice & informative


Great !!!!!!!!!! nicely Explained!!!!


do it can get failure in its work....

Thank helped me a lot....


Great work..... Really Helpful,,,
Thank you so muchhhh....

Very Nice presentation.

Thank you .




very nice & good presentation.

Thank you .

nice one thanks a lot



Hmmmmm, nice , very helpfulll

in witch case:  solenoid will trip or , Bimetal will trip

Really the diagram of MCB helped me a lot in teaching.

Thanks so much.Nice and simple explanation.Do add some video clips if possible.

it is really understandable to every one easily YES I really like it very much

easy explanation which everyone can understand. awesome ,hats off !!...
Havells 32Amp MCB Can you tell me Input and output Line ?

Many thanks for this piece. Really helped me a lot!!

very good information..

Really the Device is great..functionality!!


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