Working Principles & Benefits of Air Circuit Breakers

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.

1. 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.
2. 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.
3. 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.
4. Arc Extinguishing:

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• 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.
1. 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.
2. Resetting: After the fault is cleared, the breaker can be manually or automatically reset to resume normal operation.

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Aic Technik is engaged in the Field of High Quality Electrical, Electronic & Automation Products and solutions.

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