Time delay fuses are most commonly used in circuits subject to what type of current?

• A. Steady (DC) current
• B. AC steady current
• C. Surge (inrush) current
• D. Low-current steady

Answer: (C)

Time-delay fuses are built to tolerate short, high-current spikes without opening. They heat more gradually and need a brief overload to trigger, so they can ride through the inrush that happens when equipment starts up. This makes them the common choice for circuits with surge currents, such as motors or transformers, where the startup current can be several times the running current but only lasts a moment. In circuits with steady, non-surge current, a time-delay fuse isn’t as necessary, and fast-acting fuses are often used instead.