Circuit Breakers- Working Principles, Types And USES

Circuit Breakers- Working Principles, Types And USES

When it comes to electronic work in construction places, everything has to be taken care of with utmost priority; As electrical work is not an easy job. The precautions methods, wiring, contacting and handling of different types of circuit breakers requires exceptional skills and expertise.

So in this criteria, a circuit breaker becomes an essential need in all electrical operations on any scale. Mishaps or unfortunate errors occur frequently in the electrical and electronics industries. It will cause extensive damage to buildings, commercial buildings, homes, schools, industries, and other areas in concern. Further, for years the electrical accidents and their unfortunate casualties are increasing at regular intervals.

Even though safety precautions are taken, trusting voltage and current are unreliable. However, once circuit breakers are installed it will control the sudden rise in voltage and current. It will be valuable in the case of an accident. Circuit breakers are the pulse beat of the electrical system in construction sites.

So, What is a Circuit Breaker?

A circuit breaker is a mechanical switching device that can be regulated automatically or manually to manage the electrical power system. In other words, a circuit breaker can make or break a circuit in controlling or stabilizing the electrical arrangement. In this era of the modern system, there are different types of circuit breakers available in the market.

Different types of circuit breakers are used accordingly, likewise, in personal homes, commercial buildings and industries. Based on the requirement and the circuit system the number of circuit breakers used is determined.

Further, a circuit breaker is a piece of machinery that can,

  • In normal conditions, make or break a circuit manually or in an automated position.
  •  Automatically break a circuit in the event of an error or fault.
  •  Develop a circuit under fault conditions, either manually or automatically.

As a result, the circuit breaker can be a life saving and hazards removing tool in any situation. So it’s a must that an electrical system possesses any type of circuit breaker in their electrical systems.

Principle of Circuit Breaker

Under normal conditions, the two electrodes in the circuit breaker remain closed. When the contacts of a circuit breaker are separated due to fault or high flow of current, an arc is produced between them. As a result, the current can continue until the discharge stops.

The physical contact between the two electrodes constitutes the “ON” state of the circuit breaker. Similarly, when electrodes is set apart by manual or automatic pressure it states the “OFF” position.

The arc not only delays the current stopping process but also creates immense heat which may cause damage to the system or to the circuit breaker itself. However, a circuit breaker serves its purpose by stopping the current flow and minimising the dangers of current overflow.

The ARC Phenomenon

When a short circuit occurs, a large current flows through the circuit breaker electrodes, before the circuit. So, the overflow of current is nullified in the first instance itself.

The contact area rapidly decreases when the contacts begin to separate. A large fault current also causes an increase in current density and, as a result, a rise in temperature.

The heat generated in the medium between the contacts (typically oil or air) is sufficient to ionise the air or vaporise the oil. The ionised air or vapour acts as a conductor, causing an arc to form between the two points of contact.

The current flowing between the contacts during the arcing period is narrowed down by the resistance of the arc. The lower the current that flows between the contacts, the greater the arc resistance. It varies based on the types of circuit breakers.

Types Of Circuit Breakers

There are many ways to categorise circuit breakers. However, on a common basis, most general classification is based on the medium used for arc extinction. Finally, based on these criteria there are four types of circuit breakers as follows,

  • Oil Circuit Breaker
  • Air Circuit Breaker
  • Sulphur hexafluoride or SF6 circuit breakers 
  • Vacuum circuit breakers

Oil Circuit Breaker

Breaker oil is prone in this type of circuit, but mineral oil is mostly favourable. It acts as a better insulator than air. The moving and still contacts are sink into this insulating oil. When current is separated, carrier contacts in the oil are vaporised and decomposed in hydrogen gas, resulting in the formation of a hydrogen bubble around the arc.

This highly compressed gas bubble surrounding the arc prevents the arc from striking again after the current reaches zero crossings of the cycle. The OCB is the most traditional type of circuit breaker.

Based on the oil usage OCB types of circuit breakers  has been classified into,

  • Bulk Oil Circuit Breaker
  • Minimum Oil Circuit Breaker

Air Circuit Breaker

This circuit breaker will operate in the air, with an Arc as the quenching medium at atmospheric pressure. An oil circuit breaker replaces the air circuit breaker in many countries. We’ll talk about the oil circuit breaker later in the article. As a result, the use of an air circuit breaker up to 15KV is still a preferable option. This is because an oil circuit breaker may grab fire when handled at 15V.

The two types of circuit breakers in ACB are

  • Plain air circuit breaker
  • Airblast Circuit Breaker

Sulphur hexafluoride or SF6 circuit breakers

An SF6 circuit breaker has current-carrying contacts that operate in sulphur hexafluoride gas. It has a high electro-negativity and an excellent insulating property. It is understandable that the high affinity for absorbing free electrons. When a free electron crashes with an SF6 gas molecule, a negative ion is formed and absorbed by gas molecule.

The resulting negative ions will be much heavier than a free electron. As a result, when compared to other common gases, the overall mobility of the charged particle in SF6 gas is much lower. The mobility of charged particles is primarily responsible for current flow through a gas. As a result, it acquires very high dielectric strength for heavier and less mobile charged particles in SF6 gas. Because of its low gaseous viscosity, this gas has excellent heat transfer properties. In arc quenching media, SF6 is 100 times more effective than an air circuit breaker. It is prone in medium and high voltage electrical power systems ranging in voltage from 33KV to 800KV.

Different types of circuit breakers in SF6 circuit breakers are,

  • Single interrupter SF6 circuit breaker handled up to 220V
  • Two interrupters SF6 circuit breaker touched up to 400V
  • Four interrupters SF6 circuit breaker connected up to 715V

Vacuum circuit breakers

A vacuum circuit breaker is a circuit that uses a vacuum to extinguish an arc. It has dielectric recovery characteristics, excellent interruption, and can interrupt the high-frequency current caused by arc instability. It can be wrapt on the line frequency current.

Under normal operating conditions, the Vacuum circuit breakers principle of operation will have two contacts called electrodes that will remain closed. If a fault or error occurs in any part of the system, the trip coil of the circuit breaker is vivacious. Finally, the contact is cut apart.

Contacts in a vacuum (i.e. 10-7 to 10-5 Torr) produce an arc when opened. As soon as the arc is lit, the dielectric strength of the Circuit breaker contacts rapidly recovers, and further, the arc is extinguished.


These types of circuit breakers have revolutionized the electrical work industries as they saved many lives from electrical harm. No matter what scale electrical circuit you are working on, it’s a must, that you possess sufficient circuit breakers in your unit.

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