What is circuit breaker | Working Principle & Why Is It Important?

Hello, friends, I hope all of you are enjoying your life. In today’s tutorial, I am going to explain What is Circuit Breaker. The first-time circuit breaker was invented by Tomas Edison (who was the inventor of the United States of America) in 1879. He used this circuit breaker in lighting circuitry to minimize short circuits and overloading. Before the invention of a circuit, breaker fuses were used in different circuits but in large power and grid systems, this fuse did not operate well and did not provide protection to huge circuitry. In the grid station where large no of generators of high ratings are linked where these circuit breakers are necessary to break the faulted component from the circuitry.

Nowadays from every simple circuit to complex circuit from our house wiring to large buildings’ electrical wiring or generation system, distribution systems all use a circuit breaker to protect their load from short circuits or overloading conditions. There are many types of circuit breakers like a miniature circuit breakers, SF6, oil circuit breakers, air circuit breakers, and vacuum circuit breakers. In today’s post, we will have a look at circuit breaker construction, principle, applications, types, and some related parameters. So let’s get started with What is Circuit Breaker.

What is Circuit Breaker

• The circuit breaker is an electrical device that is used in a different circuit to provide protection from different faults like a short circuit, it breaks the circuit when a fault occurs.
• It operates both mechanically and the automatic way its construction is such that it automatically brakes circuits.

• During the construction of the breaker, it keeps in mind at which current value it will operate as nowadays such circuits are working in our power system that needs a high accuracy circuit breaker.
• In simple words, the main operation of a circuit breaker is to stop the flow of current when a fault occurs.
• Its advantage over a fuse is that after its operation of removal of a fault, it starts operation again while the fuse must be changed after fault detection.
• There are numerous ratings of circuit breakers available for small-size devices that used less current to larger circuits like switchgear panels that used high voltage.
• If we look according to its operation then it is known as OCPD (over current protection dive).

Working of Circuit Breaker

• The operation of the circuit breaker is simple it first of all senses the fault occurs in the circuit.
• In small circuits or less voltage rating breakers sensing of fault is done by the breaker itself then it breaks the circuit.
• Normally heating is produced by the large current of fault used for that detection purpose.
• While in large circuits or in grid stations for sensing fault protection relays are used that detect a fault and send a signal to the breaker then it breaks the circuit.
• For this large system, there is a need for a separate power source like a battery, but some circuit breakers get supply from current transformers.
• After sensing the fault occurring in a circuit the connections of breakers get separated, for these contacts separation mechanical energy provided by the spring or compressed air applies force on these contacts to open.
• The magnetic field of current produced by the fault is also used for the tripping of the breaker.
• In smaller circuit breakers there is a manually operated lever is installed to remove the load or again join the contacts that separated during a fault.
• While in larger circuit breakers motors are installed to provide energy to the spring that was used during tripping.

• The breaker’s contact has the ability to bear the heat produced during fault and can also bear the heat of the arc then generates during the breaking of the circuit.
• For that purpose, the materials used for the construction of breaker contacts are copper, silver, or some other material that have the ability to bear high temperature like alloys of metals.

Circuit Breaker Working Principles

A circuit breaker is an electromechanical instrument that is employed to protect electrical circuits from overloads and short circuits. It operates by interrupting the flow of current in the circuit when a fault exists

The working principle of a circuit breaker is to follow these steps:

1. The circuit breaker finds a fault condition, like an overload or a short circuit.
2. The trip mechanism of the circuit breaker is operated
3. The contacts of the circuit breaker are separated, interrupting the current flow
4. The arc which is produced between the contacts is extinguished.

The trip mechanism of a circuit breaker can be operated by different sources

• Overcurrent: The trip mechanism is activated when the current passing through the circuit breaker exceeds a predefined value.
• Short circuit: The tripping is started when a short circuit occurs in the circuit.
• Temperature: The tripping occurs when the temperature of the circuit breaker exceeds a predefined value.

Circuit Breaker Ratings

• The circuit breakers are constructed with different ratings according to their applications and the circuits for which they will install.
• The ratings of MCB (miniature circuit breaker) are fixed if we want to vary its rating then there is a need to change the complete structure of the breaker.
• But larger rating breakers have the ability to change their operation rating let’s suppose we have a breaker of four hundred ratings it can also be set to operate at three hundred ampere current.

Circuit Breaker Tripping Principles

There are 2 main tripping principles used in circuit breakers: thermal and magnetic.

• Thermal tripping is used to protect from overloads. When the current passing through the circuit breaker exceeds its rated value, the bimetallic strip in the breaker heats up and bends. This bending finally activates the tripping mechanism, which opens the breaker and stops the current flow. The time it takes for the bimetallic strip to bend and trip the breaker is based on the overload current.
• Magnetic tripping is used to protect against short circuits. When a short circuit happens, the current flowing through the circuit breaker can be very high than its rated value. This produces a strong magnetic field, which activates the magnetic tripping process. The magnetic tripping mechanism opens the breaker fastly, normally in a few milliseconds.

Circuit Breaker Structure

• The construction of a circuit breaker is very simple. It comes with these components:
  • Contacts: The contacts are the parts of the circuit breaker that make and break the circuit. They are created with a material that is resistant to arcing, like copper or silver.
  • Arc chute: The arc chute is a chamber that covered the contacts. It comes with a material that helps to extinguish the arc, like sand, or refractory powder.
  • Trip mechanism: The trip mechanism is responsible for opening the breaker when a fault happens. It is normally a spring-loaded mechanism that is activated by a bimetallic strip or using an electromagnet.
  • Enclosure: The enclosure is the external casing of the circuit breaker. It protects the inner components from the conditions and provides a mounting point for the circuit breaker.

Circuit Breaker Types

• There are different types of circuit breakers that are classified according to structure, tripping type, and voltage ratings.

Low voltage circuit Breaker

• Less voltage circuit breakers are used normally used in our homes, offices, and some small industries. Some small rating circuit breakers are discussed here.
• MCB (Miniature Circuit Breaker): the rating of this breaker is to one twenty-five amperes. The tripping current of this breaker is not adjustable.
• MCCB (Molded Case Circuit Breaker): the rating of these breakers is sixteen hundred amperes. Its operation is thermal and non-thermal.

Solid-State Circuit Breaker

• This type of circuit breaker is a new invention in circuit breaker categories that changed from mechanical to electrical the other name of a solid-state circuit breaker is a digital circuit breaker.

• It provides many benefits over the other breakers like its operating time is us, and its fault detecting power is also high also its operating life is also longer.

Magnetic circuit breakers

• This type of circuit breaker uses a solenoid for tripping purposes of disconnect connections the force used for disconnection is depended on the amount of current.
• In some circuit breakers instead of solenoid electromagnetic force is used for tripping.
• The contacts of the breakers are fastened to each other through a latch. With the increment of a current due fault, the solenoid’s pull releases the latch, due to the connections of breakers getting off.
• The breakers are mostly used in the United States of America.

Thermal-Magnetic Circuit Breaker

• The thermal-magnetic circuit breaker is mostly used in DBs (distribution boards).
• In this circuit breaker, there are 2 types of elements used for the detection of faults.

• This i^st element is an electromagnet that is used to detect the large surging current in the circuitry. Surging current is very dangerous for our home appliances like air conditioners, freezers, etc.
• The electromagnet operates very fastly when surge current flow through the circuit and disconnects the circuit.
• The 2^nd detection element in this circuit is the thermal bimetallic strip work for the less-level electric surges or for overloading conditions.
• When a fault occurs then current passes through this bimetallic strip due to current heating produced that bends the strip and removes it from the circuitry.
• Its popularity is due to that it responds very fast to a fault and starts its operation when a fault is removed.

Faqs

How is a circuit breaker different from a switch?

A switch is a device that is used to open and close an electrical circuit. A circuit breaker is also a device that is employed to open and close an electrical circuit, but it also comes with features to protect the circuit from overloading and short circuits.

The difference between a switch and a circuit breaker is that a switch does not have the feature to protect the circuit from overloads and short circuits. That defines that if a switch is employed in a circuit that experiences an overload or a short circuit, the switch will simply open, but the circuitry will still be exposed to the dangerous current.

What are the functions of a circuit breaker?

The functions of a circuit breaker are to:

• Open and close an electrical circuit.
• Protect the circuit from overloads and short circuits.
• Offer a source of isolating the circuit for maintenance or repair.

What are the important parts of circuit breakers?

The main parts of circuit breakers are:

• Contacts: The contacts are the parts of the circuit breaker that make and break the breaker
• Trip mechanism: The trip mechanism is used for opening the circuit breaker when a fault causes
• Arc chute: The arc chute is a chamber that covers the contacts. It helps to extinguish the arc that is produced when the contacts are separated.
• Enclosure: The enclosure protects the inner components of the circuit breaker from the environment.

What are the signs of a bad breaker?

The symbol of a bad breaker are:

• The breaker trips frequently.
• The breaker does not trip when it must.
• The breaker is hot to the touch.
• The breaker is leaking oil or other fluids.

What is the purpose of circuit breakers?

The purpose of circuit breakers is to protect circuits from overloads and short circuits. Overloads and short circuits can cause fires and damage to electrical instruments. Circuit breakers help to avoid these issues by opening the circuit when an overload or short circuit occurs.

What is the use of MCB?

MCB stands for miniature circuit breaker. It is a circuit breaker that is used in residential and commercial applications. MCBs are small, self-contained air circuit breakers that are made to protect circuits from overloads and short circuits.

Why does a circuit breaker work?

A circuit breaker works with the use of a trip mechanism to open the circuit when a fault occurs. The trip mechanism is normally a spring-loaded mechanism that is operated by a bimetallic strip or an electromagnet.

When a fault occurs, the bimetallic strip or the electromagnet heats up and activates the trip mechanism. This causes the contacts of the circuit breaker to separate, opening the circuit and avoiding the flow of current.

What is a fuse and circuit breaker?

A fuse is an overcurrent protection device that is normally used in low-voltage circuits. Fuses work by melting when a certain value of current flows through them. This avoids the flow of current and protects the circuit from damage.

A circuit breaker is an overcurrent protection device that is normally used in medium-voltage and high-voltage circuits. Circuit breakers work by opening the circuit when a certain amount of current flows through them. This avoids the flow of current and protects the circuit from damage.

The difference between a fuse and a circuit breaker is that a fuse is a one-time device that should be replaced after it melts. A circuit breaker can be reset and reused multiple times.

What is Sf6 circuit breaker?

Sf6 circuit breaker is a type of circuit breaker that uses sulfur hexafluoride (SF6) gas to extinguish the arc that is produced when the contacts are separated. SF6 is a very good insulator and it is also non-toxic. This makes SF6 circuit breakers a good option for applications where safety is important.

That is the detailed tutorial on the circuit breaker I have mentioned each and everything related to a circuit breaker in this post. If you have any issues or queries related to circuit breakers ask in the comments. Thanks for reading. See you in the next tutorial.