What is Circuit Breaker? – Types, Working, Applications | New Topic [2024]

In this note, we are going to discuss about a topic called “What is Circuit Breaker?“, Types, Construction, Working Principle, and Applications as well. Welcome to Poly Notes Hub, an one stop solution for Polytechnic Notes for Diploma Engineering Students.

Author Name: Arun Paul.

What is Circuit Breaker?

A circuit breaker is an electrical device that protects electrical circuits and equipment from damage caused by high current flow. It operates by automatically halting the flow of electricity in a circuit when it senses abnormal situations such as overloads or short circuits. This interruption avoids the circuit from being damaged and contributes to the safety and dependability of electrical systems. Circuit breakers are critical components in residential, commercial, and industrial applications that protect electrical equipment and prevent hazards like electrical fires.

Types of Circuit Breakers

There various types of circuit breakers –

• Minimum oil CB
• Air Blast CB
• Sulphur Hexafluoride CB
• Vacuum CB
• Air CB
• Miniature CB
• Molded case CB
• Earth leakage CB

Construction of Circuit Breakers

Circuit breakers has several key components –

• Contacts: Made of highly conductive materials such as copper or silver, they are responsible for creating and breaking electrical circuits.
• Operating mechanism: Controls when the circuit breaker opens and closes; it might be electromechanical, thermal, or magnetic.
• Arc extinguishing system: Extinguishes the arc of electricity created between the contacts as soon as they split; ways include air, oil, vacuum, or SF6.
• Insulation: Prevents electrical arcing between components while also providing mechanical support; the material used is determined by the voltage rating and ambient circumstances.
• Control panel or housing: Includes operational controls and indications, such as manual operation buttons or switches and status indicators.

Working Principle of Circuit Breakers

These are operated by continuously checking the electrical current that flows across the circuit. When the breaker senses an anomalous rise in current above its rated capacity, which indicates an overload or short circuit, it quickly cuts the circuit’s flow. This interruption occurs through a variety of mechanisms depending on the type of breaker, such as a bimetallic strip bending due to heat generated by excessive current (thermal), a solenoid coil producing a magnetic field to trip the breaker (magnetic), or a combination of mechanical triggers (electromechanical).

The CB protects the integrity of the electrical system by rapidly switching off the flow of power, preventing equipment damage, mitigating potential hazards such as electrical fires.

Basic Operation of Circuit Breaker

Circuit Breaker operation is based on three main functions –

1. Detection of Fault: Circuit breakers continuously check the electrical current that flows through a circuit. When the current reaches a predetermined threshold due to overload or short circuit, the circuit breaker identifies the issue.
2. Tripping Mechanism: When a problem is identified, the circuit breaker triggers the tripping mechanism. Depending on the circuit breaker, this mechanism may use electromagnetic, thermal, or thermal-magnetic components.
   1. Electromagnetic trip: Uses a solenoid to generate a magnetic field that pulls the contacts apart when an overload or short circuit occurs.
   2. Thermal trip: Utilizes a bimetallic strip that bends when exposed to excessive current, causing the contacts to open.
   3. Thermal-magnetic trip: Combines both thermal and electromagnetic elements for enhanced protection.
3. Disconnection of Circuit: After the tripping mechanism is activated, the circuit breaker opens its contacts, cutting off the flow of electricity via the circuit. This disconnection protects the electrical system from additional damage and decreases the risk of fire or other electrical risks.

Specifications of Circuit Breaker

Below we discuss about some specifications of CBs –

• Voltage Rating: The maximum voltage at which the CB is intended to operate safely.
• Current Rating: The maximum current that the circuit breaker can handle continuously without tripping.
• Breaking Capacity: Also known as the interrupting rating, it specifies the maximum fault current that the circuit breaker may safely interrupt without causing harm.
• Tripping Characteristics: Different CBs have distinct tripping characteristics, such as immediate, short-time delay, and long-time delay, which influence the response time under overload or short circuit conditions.
• Operating Mechanism: Circuit breakers trip and disrupt the circuit using a variety of operational modes, including thermal, magnetic, and electromechanical.

Applications of Circuit Breaker

Below we listed some uses of CBs –

1. Designed to safeguard household electrical circuits from overloads, short circuits, and other electrical failures.
2. Essential for securing machinery, motors, control systems, and other vital equipment in industrial facilities.
3. Installed in power plants, substations, and electrical grids to safeguard transformers, generators, transmission lines, and distribution networks against overloads and faults, providing a consistent power supply.