Air Circuit Breakers: Working Principle & Benefits

Introduction

ACB full form is Air Circuit Breaker. Circuit breakers are essential for the safe and effective operation of electrical systems in the area of electrical power distribution and protection. The Air Circuit Breaker (ACB) is a versatile and dependable device that stands out among the numerous types of circuit breakers available. In this article, we’ll examine the idea of an air circuit breaker, examine how it functions.

What is an Air Circuit Breaker?

Air circuit breaker is a mechanical switching device which is capable of making, carrying and breaking current under normal circuit conditions, and also carry the same for specified time and break current under specified abnormal circuit conditions. Air circuit breakers are used to distribute electric energy and protect lines and power supply equipment from faults such as overloads, under voltages, short circuits, etc.

Working Principles of Air Circuit Breakers

1. Arc Interruption Mechanism:

High current passes through the ACB when an electrical malfunction, like a short circuit or overload, takes place. An electric arc forms between the circuit breaker’s contacts as a result of the high current. Even after the circuit breaker has tripped, the arc creates a conductive route that keeps the current flowing.

ACBs use a number of arc quenching techniques to stop this arc. The “blast effect” or “arc chute” principle is the most widely used technique. The ACB sends a high-pressure stream of air through specially constructed arc chutes when the arc is recognized. The electric arc is effectively put out by the quick air expansion in these arc chutes, which also allows the contacts to separate and stop the current flow.

2. Magnetic and Thermal Tripping Mechanism:

Thermo- and magnetic tripping mechanisms are built into ACBs to detect abnormal current conditions and start a circuit interruption. While the magnetic tripping mechanism reacts to short-circuit currents, the thermal tripping mechanism recognizes long-term overloads. These tripping devices activate the opening mechanism, starting the arc interruption process, when the current rises above a predetermined level.

3. Normal Operation:

Under regular conditions, current flows through the breaker without interruption. The contacts inside the ACB remain closed, allowing electricity to pass through freely.

4. Fault Detection:

When the current exceeds the pre-set limit (due to overload or short circuit), the breaker detects this abnormal condition using sensors such as overcurrent relays or thermal relays. These relays trigger the breaker to act.

5. Arc Formation:

Upon detecting a fault, the breaker opens its contacts. As the contacts separate, an electrical arc forms between them due to the high voltage across the gap. This arc, if not controlled, can damage the breaker and the electrical system.

6. Arc Extinguishing:

• • The air circuit breaker is equipped with arc chutes, which help in dividing the arc into smaller segments. This increases the arc’s surface area and cools it down.
  • Air is blown across the arc or the arc is guided into the arc chute, where it is stretched and cooled. As the arc length increases and the temperature decreases, the arc extinguishes.

7. Interruption of Current Flow:

Once the arc is extinguished, the electrical circuit is effectively broken, stopping the flow of current and preventing further damage to the system.

8. Resetting:

After the fault is cleared, the breaker can be manually or automatically reset to resume normal operation.

Air circuit breakers’ benefits

Enhanced Safety:

ACBs provide protection against overloads, short circuits, and electrical faults, helping to prevent damage to electrical systems and ensuring the safety of both equipment and personnel

High Current Capacity:

They are capable of handling and breaking high levels of current, making them suitable for large electrical installations in industries and power stations.

Adjustable Trip Settings:

ACBs allow for the customization of protection settings, enabling precise control over the timing and level of current at which the breaker trips.

Reusability:

Once the fault is cleared, ACBs can be reset without needing to replace components, offering a cost-effective and efficient solution over time.

Durability:

They are designed for long-term use and can withstand harsh environmental conditions, including high temperature and humidity.

Remote Operation:

ACBs can be operated remotely, providing convenience and improving safety during maintenance or fault conditions.

Conclusion

A key element of contemporary electrical systems, the Air Circuit Breaker (ACB) ensures the security and effective operation of power distribution networks. ACBs efficiently stop current flow during electrical disturbances by utilizing arc quenching techniques and trustworthy tripping mechanisms.

As technology continues to advance, the importance of Air Circuit Breakers will only grow, ensuring the continued reliability and safety of our electrical infrastructure for years to come.