Interrupting rating is defined as what?

• A. The highest continuous current the device can carry
• B. The maximum resistance the device can tolerate
• C. The highest current at rated voltage that the device is identified to interrupt under a standard test condition
• D. The nominal voltage rating for interruption

Answer: (C)

Interrupting rating is about the device’s ability to safely break fault current. It is defined as the highest current, at the device’s rated voltage, that the device is identified to interrupt under standard test conditions. This expresses the breaking or interrupting capacity of the device when a short circuit occurs, not how much current it can carry continuously in normal operation or any measure of resistance. It’s also more than just a nominal voltage rating for interruption; it combines voltage and current under prescribed conditions to specify what the device can safely interrupt. In practice, you choose a device whose interrupting rating meets or exceeds the system’s prospective short-circuit current at the operating voltage. For example, a breaker rated to interrupt 10 kA at 480V can safely clear faults up to 10 kA at that voltage.