What is the max current an overprotective device will carry indefinitely without tripping?

• A. The max current an overprotective device will carry indefinitely without tripping
• B. The current rating that will trip in seconds
• C. The short circuit current it can break without exploding
• D. The voltage rating of the device

Answer: (A)

The concept being tested is the continuous operating current of an overcurrent protective device. This is the maximum current the device can carry indefinitely without tripping. It’s the rating that tells you how much load you can run through the device in steady state without it opening the circuit. If the current stays at or below this level, the device stays closed under normal conditions.

That’s why the correct choice is the one describing the maximum current the device can carry indefinitely without tripping. The other ideas refer to different characteristics: the trip current (which is the threshold that will cause the device to trip, not the continuous limit), the short-circuit or interrupting capacity (how much fault current it can safely interrupt, not normal operation), and the voltage rating (the voltage it is designed to operate at, not how much current).