Dual-element or time-delay fuses can provide motor overload protection but have the disadvantage of ______?

• A. They are expensive
• B. They blow too slowly
• C. They are not reliable
• D. Being nonrenewable

Answer: (D)

Dual-element and time-delay fuses are chosen for motor overload protection because they tolerate brief inrush currents and still open when a sustained fault occurs, protecting the motor windings. The main drawback is that these fuses are single-use devices; once they have operated, they must be replaced with a new fuse of the correct rating. This means downtime to replace the fuse and maintain stock of spares, unlike circuit breakers that can be reset after a fault. The other options don’t fit as well: these fuses aren’t inherently expensive or unreliable by design, and the time-delay feature is meant to prevent nuisance tripping, not to imply slow protection.