What type of fuse is designed to open on the first 1/4 of the fault cycle?

The correct answer is that a silver sand fuse is designed to open on the first quarter of the fault cycle. Silver sand fuses are specifically constructed to have quick response times due to their design, which involves a conductive silver element embedded in a sand medium. This allows the fuse to react rapidly to overcurrent conditions, minimizing the duration of fault energy and protecting downstream equipment from potential damage.

In contrast, glass fuses, while relatively quick, do not typically have the same fast-opening characteristics of silver sand fuses. Cartridge fuses are designed for higher current applications and can have varying trip characteristics depending on the design but generally do not open as quickly as silver sand fuses. Time-delay fuses are particularly designed to withstand temporary surges of current and are engineered to remain intact during short overloads without opening immediately, which is contrary to the requirement of opening within the first quarter of the fault cycle.

Understanding the specific applications and response characteristics of these fuses is critical for proper protective device selection, ensuring both safety and reliability in electrical systems.