An air blast circuit breaker is a type of circuit breaker used in high-voltage electrical systems to interrupt or break the flow of current in a circuit. It operates by using a blast of compressed air to extinguish the arc formed between the contacts when the circuit breaker opens.

Here's how an air blast circuit breaker works:

1. Contact Operation: Similar to other types of circuit breakers, an air blast circuit breaker consists of contacts that open and close to control the flow of current in the circuit. When the circuit breaker is closed, the contacts are in physical contact, allowing current to pass through the circuit.

2. Arc Formation: When the circuit breaker is opened to interrupt the current flow, an arc may form between the contacts due to the ionization of the surrounding air. This arc can continue to conduct current even after the contacts have physically separated, posing a risk of damage to the equipment and the electrical system.

3. Compressed Air Blast: To extinguish the arc quickly and effectively, an air blast circuit breaker utilizes a blast of compressed air. When the circuit breaker opens, a high-pressure air flow is directed across the arc, disrupting the ionized gases and cooling the arc plasma.

4. Arc Extinction: The rapid expansion of the compressed air blast creates a pressure gradient that forces the ionized gases away from the gap between the contacts, effectively extinguishing the arc. As a result, the current flow is interrupted, and the circuit is safely de-energized.

5. Resetting and Reclosing: After the arc is extinguished, the circuit breaker can be reset and reclosed to restore power to the circuit. The contacts come back into physical contact, allowing current to flow once again.

Air blast circuit breakers are typically used in high-voltage applications, such as in substations and power transmission networks, where they offer fast and reliable interruption of heavy currents. They are particularly well-suited for interrupting short-circuit currents, as the compressed air blast provides efficient arc extinction even under high fault currents.

While air blast circuit breakers are effective and reliable, they require a source of compressed air, which adds complexity to their installation and maintenance compared to other types of circuit breakers. Additionally, advancements in technology have led to the development of alternatives such as vacuum circuit breakers and SF6 circuit breakers, which offer similar performance with fewer environmental concerns and maintenance requirements.