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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



Comments (11)

I likeD it..I had seen it

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

explanation is strong. thanks. regards, raja giri



gr8 work.. arc quenching

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

wow, very nice. 

wow, very nice.





mcb is a best of electrical

mcb is a best of electrical component


nice & informative 

nice & informative


Great !!!!!!!!!! nicely

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


do it can get failure in its

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

Thank helped me a

Thank helped me a lot....


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