How does a multi-pole breaker provide overcurrent protection?

A multi-pole breaker is designed to trip all poles simultaneously in response to an overcurrent condition, providing comprehensive protection for the entire circuit. This simultaneous tripping ensures that all phases connected to the breaker are isolated at the same time, which is critical for preventing damage to equipment and maintaining safety during fault conditions.

When a fault occurs, such as a short circuit or overload, the current in one or more phases may increase dramatically. By tripping all poles together, the breaker effectively disconnects the entire circuit, preventing further current flow and protecting downstream equipment from potential damage due to excessive current. This approach also helps maintain the balance of the load across the phases, which is important in three-phase systems.

Other options relate to different operational characteristics that do not accurately describe the function of a multi-pole breaker in terms of overcurrent protection. For example, isolating phases separately or allowing individual circuits to continue operating while one trips does not align with the multi-pole breaker's designed function of ensuring all phases are disconnected simultaneously during a fault. Additionally, automatic resetting after a fault condition does not characterize a multi-pole breaker, as these devices typically require manual resetting after being tripped.