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What is a Circuit Breaker? Types, Functions and Working Principle

Ever experienced that sinking feeling when you’re behind on a project and your laptop gives up on you? Picture this: racing against the clock, desperately plugging in the charger, and boom – darkness engulfs the room. So, what’s the deal with that? In a panic, you stumble around, searching for the switch that will bring the light back. And miraculously, when it does, you’re relieved but left wondering what caused the chaos.

Well, it’s a circuit breaker tripping, causing all the chaos. Circuit breakers are an essential component in electrical systems, playing a vital role in protecting us from potential hazards. Understanding the different types of circuit breakers, their functions, and the working mechanism behind them empowers us to make informed decisions about electrical safety.

In situations where you lack this knowledge, reaching out to the Antipode Power Solution team of experienced professionals is a smart move. Our team is well-equipped to handle all your electrical needs and ensure the safety and reliability of your electrical infrastructure.

What is a Circuit Breaker?

A circuit breaker is an electrical switching device designed to protect you from electrical shock by automatically interrupting or breaking an electrical circuit when it detects excess current flowing through it. It plays a crucial role in protecting electrical circuits and preventing damage to appliances, wiring, or other electrical components in the event of a short circuit, overload, or other power surge. They’re crucial safety devices used in residential, commercial, and industrial power systems.

While often confused, circuit breakers or fuses share the common purpose of protecting entire systems from overcurrent and preventing electrical fires. Despite this similarity, they operate differently and possess distinct characteristics.

Circuit breakers vs. fuse

  • Circuit breakers employ a switch-like mechanism capable of manual or automatic tripping to interrupt electricity flow upon detecting overcurrent or faults. Notably, they are resettable, enabling multiple uses after tripping incidents.
  • Fuses consist of slender wires that melt under excessive current, breaking the circuit and halting electricity flow. They are single-use devices; once the wire melts, the fuse requires replacement. The operation of fuses is triggered by the heat generated during overcurrent, leading to the melting of the wire and the subsequent opening of the circuit.

Components of circuit breaker

The main elements that make up a circuit breaker are:

  1. Switch: A switch or lever serves as the main control, allowing the circuit to be manually opened or closed.
  2. Electromagnetic or Thermal Trip Unit: This component detects abnormal current conditions. In the case of an overload or short circuit, it triggers the mechanism to open the circuit and interrupt the electric flow.
  3. Contacts: Circuit breaker contacts are conductive plates that open or close the circuit. When the circuit breaker is in the closed position, the contacts allow the current to flow, and when open, they break the current.
  4. Arc Extinguisher: Designed to extinguish the arc that forms between the contacts during opening. This is crucial for preventing damage to the contacts and ensuring a safe interruption of the current.
  5. Operating Mechanism: This mechanism controls the opening and closing of the contacts, often utilising a spring-loaded or motor-driven mechanism.

Also Read: How long do circuit breakers last?

How Does a Circuit Breaker Work? Main Working Principle


The main working principle of a circuit breaker revolves around its ability to disrupt the flow of electrical current in a circuit when necessary. The key components and steps in the operation of a circuit breaker are as follows:

  1. Detection of Faults: Firstly, circuit breakers, equipped with sensors and mechanisms, identify abnormal conditions in the electric circuit, such as overcurrent, electrical short circuits, or faults. This detection process is usually integrated within the device, particularly in small mains and low-voltage circuit breakers.
  2. Electromagnetic or Thermal Tripping: Following detection, the circuit breaker employs two primary tripping mechanisms – electromagnetic and thermal. In cases of overcurrent, the electromagnetic tripping mechanism responds to the excess current’s magnetic field. Meanwhile, the thermal tripping mechanism is triggered by the heat generated during overcurrent, causing a bimetallic strip to bend and initiate the circuit breaker’s trip.
  3. Opening the Contacts: Subsequently, the breaker proceeds to open its contacts, the conducting plates within the device. This action creates a gap in the circuit, effectively cutting the power and interrupting the flow of electric current. This interruption is crucial for preventing further damage to the circuit and associated devices.
  4. Interrupting the Current Flow: When the contacts open, it creates a gap in the circuit, effectively cutting the power and breaking the flow of electric current. This cutting-off is crucial for preventing further damage to the circuit and associated devices.
  5. Arc Extinction: During the opening of contacts, there’s a potential for an electric arc to form due to the existing current. To address this, circuit breakers incorporate methods such as arc chutes or extinguishing mediums like oil or gas, ensuring a safe interruption.
  6. Manual or Automatic Reset: Finally, some circuit breakers offer a manual reset option. This feature allows users to close the contacts after rectifying the fault, thereby restoring the electrical power supply to the breaker panel.

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Functions of an electrical safety device: Circuit Breaker

The key functions of a circuit breaker include:

  1. Overcurrent Protection: Designed to detect and respond to overcurrent conditions in a power circuit when the current exceeds a predetermined threshold, the circuit breaker stops the flow of electricity, safeguarding the power source and preventing potential damage to the circuit and connected devices.
  2. Short Circuit Protection: In the event of a short circuit, where a low-resistance path is created, circuit breakers act swiftly to disconnect the circuit. This rapid response helps prevent overheating and the risk of electrical fires.
  3. Device Protection: Circuit breakers protect electrical appliances, equipment, and wiring from damage caused by excessive current. By disconnecting the power during faults, they ensure the longevity and proper functioning of connected devices.
  4. Selective Coordination: In complex electrical systems, circuit breakers are often selectively coordinated to isolate faults in specific sections while keeping the rest of the system operational. This coordination enhances the reliability and continuity of electrical supply in critical applications.
  5. Manual Control: Circuit breakers offer a manual control mechanism, allowing users to manually open or close the contacts. This feature is useful for maintenance activities or when troubleshooting electrical issues.
  6. Arc Fault Protection: Advanced circuit breakers may include arc fault detection capabilities. They can identify and respond to the presence of dangerous arcing conditions, further enhancing safety in residential and commercial settings.
  7. Ground Fault Protection: In specific circuits, such as those in bathrooms or kitchens, circuit breakers with Ground Fault Circuit Interrupter (GFCI) features are employed. These devices detect imbalances in electric flux to the ground, providing an additional layer of protection against electric shock.

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Different Types of Circuit Breakers

Air Circuit Breaker (ACB)

An Air Circuit Breaker is a type of circuit breaker that uses air as the arc-quenching medium to cut the flow of electricity in a circuit. It is commonly used in low-voltage power distribution systems for industrial and commercial applications.

The ACB rapidly detects and responds to electrical faults, such as overcurrent or short circuits, using an electromagnetic trip mechanism. It efficiently opens its contacts, interrupting the electric arc with surrounding air. After clearing the fault, manual reset closes the contacts, restoring the circuit to normal operation swiftly and ensuring overall system reliability and safety

Oil Circuit Breakers (OCB)

Oil Circuit Breakers are utilised in high-voltage applications, particularly in power transmission and distribution systems. These breakers cut the flow of electrical current by utilising oil as an arc-quenching medium. When a fault occurs, the contacts open, generating an electric arc that is rapidly extinguished by the surrounding oil. The oil serves dual purposes, acting as both a coolant for the contacts and an insulator to prevent arc restriking.

Miniature Circuit Breaker (MCB)

A Miniature Circuit Breaker is a type of electrical protection device commonly used in residential, commercial, and industrial applications. MCBs are compact, space-saving devices that provide reliable protection for electric circuits. They operate on the principle of thermal and magnetic tripping mechanisms. In the case of an overload, the bimetallic strip within the MCB bends due to heat, tripping the breaker. MCBs are quick to respond, easy to reset, and provide localised protection for individual circuits without affecting the entire electrical distribution board.

 SF6 Circuit Breakers

Sulfur Hexafluoride circuit breakers are used in high-voltage applications for power transmission and distribution. They utilise sulfur hexafluoride (SF6) gas as the insulating and arc-quenching medium. When a fault occurs, the contacts open, and SF6 rapidly extinguishes the electric arc, preventing further current flow. Known for their compact design and high interrupting capacity, SF6 circuit breakers are effective in specific high-voltage scenarios.

Vacuum Circuit Breakers (VCB)

Used in medium to high-voltage applications, the vacuum circuit breaker uses a vacuum as the arc-quenching medium to break the flow of electric current when necessary. The vacuum offers superior insulating and arc-extinguishing properties, making VCBs suitable for various industrial and power distribution systems. As a result, VCBs are known for their reliability and low maintenance requirements compared to other types of breaker switches.

Molded Case Circuit Breakers (MCCB)

Molded-Case Circuit Breakers are electrical protection devices designed for low to medium-voltage applications. Housed in a moulded case for insulation, they automatically break electrical flow during overloads and electrical faults, safeguarding connected devices and preventing damage to the power system. With adjustable trip settings and the ability to manually reset, MCCBs are versatile components widely used in residential, commercial, and industrial settings for reliable and customisable circuit protection.

How do you identify different types of breakers?

Wondering why identification matters? So, when they decide to leave you in the dark, you’ll know your breakers, and darkness won’t catch you off guard!

  1. Identify the voltage rating of the power circuit breaker, ensuring it matches the system it is intended to protect.
  2. Consider the current-carrying capacity of the breaker, ensuring it is suitable for the expected load of the power circuit.
  3. Determine the number of poles in the breaker. Single-pole breakers control one hot wire, while double-pole breakers handle two hot wires simultaneously.
  4. Examine the trip mechanism of the breaker, whether it is thermal, magnetic, or a combination of both.
  5. Consider the intended application of the breaker, whether it is designed for residential, commercial, or industrial use. Additionally, take note of any special features the breaker may have.

Feeling a bit puzzled about circuit breakers? Don’t fret! Antipodes Power is here to brighten the path for you. If you’re in confusion about volts, amps, poles, trips, or just need some electrical enlightenment, give us a buzz!

Our team is amped up and ready to decode the shockingly good world of breakers. ⚡💡 Reach out to us now – where confusion gets switched off, and solutions power up!


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