When a short circuit occurs, a current limiting fuse, within its current limiting range, opens within ½ cycle. This prevents the damaging overcurrent to reach its maximum instantaneous short-circuit value in the circuit if that fuse were replaced with a solid conductor of comparable oppositional characteristics to current flow. The instantaneous peak let-though current is the actual maximum let-through current value in the circuit before the fuse opens and clears the circuit under short circuit conditions.

Example Current Limitation Sine Wave