What is the interrupting ratings on AC-rated circuit breakers applicable to?

The interrupting rating of a circuit breaker is a critical specification that indicates the maximum fault current the breaker can safely interrupt without being damaged or failing to operate as intended. This rating is specifically applicable to AC systems, as AC circuit breakers are designed to interrupt alternating current under fault conditions effectively.

In AC systems, the current periodically goes to zero, allowing the breaker to interrupt the circuit without the risk of maintaining an arc, which is a challenge in DC systems where the current does not naturally curve to zero in each cycle. Therefore, the interrupting ratings for AC circuit breakers are specifically established to ensure reliable operation under alternating current conditions and reflect the performance necessary to handle typical fault scenarios found in these systems.

The terminology and specifications are tailored to the dynamics of AC waveforms, meaning that the ratings do not transfer directly to DC systems, which require different characteristics due to their continuous current flow. Thus, the correct focus on the interrupting ratings in this context is on AC systems.