Which term describes the maximum fault current a circuit breaker can interrupt without damage at a given voltage?

• A. Breaking capacity
• B. Tripping current
• C. Operating current
• D. Voltage withstand rating

Answer: (A)

The maximum fault current a circuit breaker can interrupt without damage at a given voltage is described by its breaking capacity (also called interrupting capacity). This rating tells you the highest short-circuit current the breaker can safely interrupt while the contacts and internal mechanism stay intact and the device remains able to clear the fault. It’s expressed in kiloamperes (kA) at a specified system voltage and reflects the device’s thermal and electrical limits during a fault, not the current at which it trips under normal conditions.

Tripping current, by contrast, is the current level that causes the breaker to open to protect the circuit during an overcurrent event, which is about when it operates, not how much fault current it can interrupt. Operating current is the normal load current the breaker carries during regular operation. Voltage withstand rating relates to the dielectric strength of the breaker—how much voltage it can withstand without breaking down—rather than its ability to interrupt a fault current.