What is a Circuit Breaker? How is it Work?

Circuit Breaker is a name we have all heard and seen. We know how important circuit breakers are to protect electronics machinery. Many of us do not know the structure of circuit breaker and how it works. Today we will learn more about these issues. So let’s see what topics will be in today’s article.

What is a circuit breaker?

Simply put, a circuit breaker is an automatic device that provides security. This means that it is a device that protects electrical and electronics equipment. When there is excessive power flow in the line (in the machinery) any accident can happen which protects the circ’uit breaker. Circ’uit Breaker is a type of device that can open or close a circuit in all conditions (no-load condition, full load condition, and faulty condition). In other words, a circ’uit breaker is a device that automatically disconnects a faulty line from the source.

What does a circuit breaker do?

A voltage higher than the design voltage in a circuit is actually a circ’uit breaker that automatically protects the circuit.

  • In case of a short circuit in AC line (line to line or line to neutral).
  • If there is excess load.
  • When the voltage rises.

Types of circuit breakers

Based on arc or fire extinguishing

  • Well circ’uit breaker.
  • Air circ’uit breaker.
  • Sulfur hexafluoride circ’uit breaker.
  • Vacuum circ’uit breaker.

Based on service

  • Outdoor Circ’uit Breaker.
  • Indoor circ’uit breaker.

Based on the operating mechanism

  • Spring operated circ’uit breaker.
  • Pneumatic circ’uit breaker.
  • Hydro-electric circ’uit breaker.

The voltage label is based on the installation

  • High voltage circ’uit breaker
  • Medium voltage circ’uit breaker
  • Low-voltage circ’uit breaker

It can also be divided into the following ways

  • Magnetic circ’uit breaker.
  • Common trip circ’uit breaker.
  • Thermal circ’uit breaker.
  • Disconnecting circ’uit breaker.
  • Carbon dioxide circ’uit breaker.

Circuit Breaker consists of two main parts.

  • Fixed contact.
  • Moving contact.

We usually use MCB-Miniature Circuit Breaker at home. Below is a picture of the miniature circ’uit breaker in its context.

It is a widely used circuit bre’aker in the home. Figure operating level, arc splitter, moving contact, fixed contact, trip coil, etc.

circuit.b structure


Here are some basic steps you can take to begin the process of preparation for mediation.

  • Circ’uit Breaker is operated manually (remote control or other) under normal conditions.
  • Circuit Bre’aker operates automatically when faulty.
  • Under normal conditions, moving and fixed contacts are in the same contact and electricity flows through the circuit.
  • Both the CT and the relay work for the automatic interruption.

Steps to work

  • When more current than the design current is flowing in the line (due to excess current fault) then the current transformer (CT) will reduce the excess current and send it to the relay coil.
  • When peak current (currently greater than the specified current) occurs in the relay coil, the relay coil becomes active and closes the moving contact circuit of the relay.
  • The trip coil is then energized by the battery source of the trip circuit and breaks the contact.


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