Which fuses are current-limiting short-circuit protective devices and are marked current limiting?

• A. Class R, J, CF, and L fuses
• B. Class J and CF fuses only
• C. Class R fuses only
• D. Class H fuses only

Answer: (A)

Current-limiting fuses are designed to interrupt a short-circuit extremely quickly, so the energy that gets through to conductors and equipment is kept to a minimum. They are usually marked with a current-limiting designation on the body, signaling that they provide this fast protection and energy limiting.

Among common fuse families, the ones that are both current-limiting and carry that marking are the R, J, CF, and L fuses. They are built to respond fast to short circuits and are explicitly labeled as current-limiting, which helps ensure they’re chosen for applications where limiting fault current is important.

Other fuse types might be fast-acting in some cases, but they aren’t guaranteed to be current-limiting or to bear the current-limiting marking, so they don’t meet both criteria described in the question.