NFPA 70E informational Note to Table 130.7(C)(15)(a) indicates the typical fault clearing time for current-limiting fuses as 0.5 cycles when the fault current is within the current-limiting range.

• A. 0.5 cycles
• B. 1.5 cycles
• C. 3 cycles
• D. 0 cycles

Answer: (A)

Fast fault clearing with current-limiting fuses happens when the fault current stays within the fuse’s current-limiting range. The NFPA 70E informational note tells us that the typical clearing time in this scenario is about half a power cycle. That means the arc is interrupted very quickly, significantly reducing the arc duration and the energy released compared with longer clearing times. Among the options, that half-cycle timing best matches how these fuses behave in practice. The other timings imply slower clearing, which would allow more energy to be released, or instantaneous clearing which isn’t how current-limiting fuses operate. Real-world clearing times can vary with the exact fault current and fuse type, but the half-cycle figure is the standard reference for faults within the current-limiting range.