Red Seal Electrician Practice
Wiring and componentsQuestion 816 of 1506

Why is a slow-blow (time-delay) fuse a good choice for protecting a motor?

  1. It opens faster than any other type on a small overload.
  2. It has a lower current rating for the same wire size.
  3. It adds resistance that limits the starting current.
  4. It lets the brief inrush at start pass without opening.
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Correct answer: It lets the brief inrush at start pass without opening.

A fast fuse would open on the normal starting surge, so the motor could never start. A time-delay fuse tolerates the surge.

Source: Lessons in Electric Circuits I: DC (Kuphaldt), 12.4: Fuses

Practice wiring and components

Questions last reviewed: 18 October 2026