In this note, we are going to know About Air Blast Circuit Breaker, about its Construction, Working Principle, Advantages, Disadvantages, and Applications as well. Welcome to Poly Notes Hub, an one stop solution for Diploma Engineering Notes for Polytechnic Students.
Author Name: Arun Paul.
What is Air Blast Circuit Breaker?
An Air Blast Circuit Breaker is a device found in electrical systems that interrupts or stops the flow of electricity in abnormal situations such as short circuits or overloads. It consists of fixed and moving contacts in an insulated chamber filled with high-pressure air. When a fault occurs, the contacts instantly separate due to a burst of compressed air, extinguishing the electrical arc that developed between them.
This fast interruption serves to prevent equipment damage and ensures that the power system operates safely. While Air Blast Circuit Breakers were originally widely employed in high-voltage applications, they have been mostly supplanted by newer technologies such as vacuum and SF6 circuit breakers, however, they are still utilized in certain situations where their benefits are advantageous.
Construction of Air Blast Circuit Breaker
Below we discuss the construction of this device –
- Fixed Contact: This is a fixed component of the circuit breaker that stays in place during operation. It is often made of a sturdy conductive substance like copper or copper alloys.
- Moving Contact: The moving contact is intended to establish or break electrical connections with the stationary contact. It can be mechanically manipulated to open or close the circuit. The moving contact is typically constructed of conductive material and connects to the circuit breaker’s functioning mechanism.
- Arcing Chamber: The arcing chamber is an insulated enclosure in which the arc generated during a circuit disruption is contained and extinguished. It is filled with high-pressure air, which helps to quickly cool and quench the arc.
- Spring Closing Mechanism: Under normal operating conditions, the circuit breaker connections are closed using a spring-loaded mechanism. When the circuit breaker is open, the spring compresses. When it’s time to close the contacts, the spring is released, causing them to move closer together and make electrical contact.
- Air Reservoir Tank: The air reservoir tank holds compressed air, which is utilized to provide the blast necessary to extinguish the arc during circuit disruption. It ensures that a sufficient supply of high-pressure air is available whenever the circuit breaker is activated.
- Series Isolator: A series isolator is occasionally included with the circuit breaker assembly. This isolator isolates the circuit breaker from the electricity system for maintenance or repair. It permits the circuit breaker to be unplugged from the electrical system while still providing a safe working environment for the equipment.
Working Principle of ABCB
An Air Blast Circuit Breaker or ABCB operates in multiple steps. Initially, the circuit breaker contacts are open. During normal functioning, electricity passes via the closed circuit, transferring power to the load. If a malfunction arises in the electrical system, such as a short circuit or overload, protective relays detect the excess current flowing through the circuit. After receiving the signal from the protective relays, the circuit breaker’s trip mechanism is engaged, causing the circuit breaker contacts to open. As the contacts split, the flow of current creates an electrical arc between them.
To extinguish the arc, a burst of compressed air is directed into the arcing chamber, cooling and quenching it. After the arc is extinguished, the circuit breaker disconnects the malfunctioning component of the electrical system from the remainder of the network. After the problem has been cleared and the system is safe, the circuit breaker can be manually or automatically reset, bringing the contacts back into the closed position and allowing regular electrical system function to resume.
Advantages of ABCB
Below we listed some merits of this circuit breaker –
- They can successfully handle huge fault currents and interrupt high currents.
- These type of circuit breakers are very fast and reliable in operation.
- It has a long service life.
Disadvantages of ABCB
Below we listed some demerits of this circuit breaker –
- Compared to other varieties, these circuit breakers are usually heavier and bulkier.
- Any compressed air leak from the system may have an impact on the circuit breaker’s dependability and functionality.
- The initial cost of installing Air Blast Circuit Breakers is high.