Which of the following types of fuses is best for protecting a motor feeder?

The best type of fuse for protecting a motor feeder is the dual element time-delay fuse. This fuse is designed to accommodate the inrush current that electric motors experience when they start. During this initial phase, the motor draws significantly more current than its running load, which can be several times higher than the rated current. The dual element time-delay fuse has two elements: one that responds quickly to overload conditions and another that provides a delay for temporary overloads, such as those caused by motor starting.

This characteristic is particularly important in industrial settings where motors frequently start and stop. If a fast-acting fuse were used instead, it could blow during the initial inrush current, leading to unnecessary downtime and interruptions to the operation. Similarly, while current limiting fuses are useful for protecting against short circuits, they may not provide the necessary delay for motor starting currents. Cartridge fuses can protect circuits but do not offer the same time-delay capability specifically tailored for motors. Thus, the dual element time-delay fuse represents the most effective choice for protecting motor feeders in industrial applications.