Circuit breaker - What it is and how it works

Circuit breaker - What it is and how it works


Circuit breaker


Circuit breaker is an automatic switching device used to protect electrical power systems from the excessive flow of electric current. 

When an overload or short circuit occurs in an electrical circuit, it automatically disconnects the entire power system and saved the system. 

The circuit breaker is like the Fuse but it is a little advanced level device compared to the Fuse. 

Fuses and circuit breakers do the same work when overloads occur in the circuit, which means they break the power system. 

But the fuse needs to be replaced repeatedly from the circuit where the circuit breaker can automatically do this task.

Circuit breaker - What it is and how it works

There are three types of circuit breakers for protective household electrical connections. 

For example - Miniature Circuit Breaker (MCB), Moulded Case Circuit Breaker (MCCB), and Residual Current Circuit Breaker (RCCB)

According to the construction of Circuit breaker, there are different types of Circuit breakers. like - Air Circuit Breaker, SF6 Circuit Breaker, Vacuum Circuit Breaker, Oil Circuit Breaker.

How Circuit breaker work?


There are different types of circuit breakers for operating different voltages. Different techniques are used for their construction. 

But basically, the circuit breaker's job is to develop an automatic on/off system that protects the system when overload and short circuits occur. 


In this tutorial, we will learn about the structure of how circuit breakers turn on / off. Here is a diagram showing the circuit breaker parts. We will know how these parts work.


Circuit breaker - What it is and how it works


In the picture above you can see the various parts of a circuit breaker. The circuit breaker is installed between the load from the Bus-bar. 

And this circuit breaker's system contains a C.T (current transformer) that gives the relay an excessive electrical signal. 

When this excessive flow occurs in the electrical circuit, then the relay receives a signal from the C.T (current transformer) and becomes active. 

After the relay is activated it closes the trip circuit. In the trip Circuit, a battery is installed and for the circuit being closed the electrical current is starting to flow. 

As a result, the trip coil gets magnetized and the moving contact in the circuit breaker gets detached from the power line and that the entire circuit is disconnected from the power system. In this way, the circuit breaker protects the entire power system. 


Circuit breaker consists of a fixed contact and a moving contact. The moving contact is handled by the trip coil. 

When the moving contact is tipped through the trip coil then it produces sparks for the high voltage. 

So in circuit breakers, various mediums are used to reduce this spark, such as Air, SF6 gas, Oil, etc. These mediums are used depending on the voltage applied in the power system. 



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