An air circuit breaker (ACB) has to create an arc voltage as part of its essential operation to safely interrupt the flow of current during a fault or overload condition in an electrical circuit. When a fault occurs, such as a short circuit or overload, the current flowing through the ACB can reach very high levels. To interrupt this high current safely and effectively, the ACB uses a mechanism that generates an electric arc between its contacts. The arc voltage is the voltage required to sustain the arc between the contacts once they begin to separate. This arc voltage allows the current to be diverted away from the faulted circuit and extinguished through controlled means, thereby protecting the electrical system from damage and ensuring safe operation.
An arc is produced in a circuit breaker as a result of the electrical breakdown of air or other insulating medium between the contacts when they are separated. During the opening operation of the circuit breaker, especially under fault conditions, the current flowing through the contacts ionizes the air between them. This ionization creates a conductive path or arc that sustains the flow of current even after the contacts have moved apart. The arc is essentially a plasma channel with high temperature and ionized gases that allow the current to continue flowing until it is extinguished or interrupted by the circuit breaker’s mechanisms.
In an air circuit breaker (ACB), the arc chute is a crucial component designed to facilitate the extinction of the arc once it is initiated between the contacts. The function of the arc chute is to guide and channel the arc into a controlled path where it can be cooled, deionized, and eventually extinguished. The arc chute typically consists of several plates or grids arranged in a specific configuration to maximize the length of the arc path. By forcing the arc to travel through the arc chute, the ACB enhances the cooling and deionization process, thereby ensuring efficient interruption of the fault current and preventing re-ignition of the arc.
The arc voltage in a circuit breaker refers to the voltage that appears across the contacts once an arc is established between them during the opening operation. This voltage is necessary to sustain the arc and keep the current flowing until the breaker’s mechanisms can safely extinguish it. The magnitude of the arc voltage depends on factors such as the current magnitude, the type of fault or overload, and the design of the circuit breaker. Circuit breakers are designed to handle and interrupt arcs by incorporating features like arc chutes, arc extinguishing devices, and controlled contact separation distances to manage and safely extinguish the arc voltage during operation.