Code Standards and Practices Level 3 Practice Test

The main idea is that fuses are designed to interrupt fault currents, such as short circuits or ground faults, up to their specified interrupting rating. The interrupting rating is the maximum current the fuse can safely interrupt without being damaged. Under normal operation the fuse carries the load current, but when a fault occurs and the current spikes to fault level, the fuse melts and opens to protect the circuit. Inductive or magnetic characteristics describe aspects of the current during faults, but the critical distinction is fault current. Overload currents are not what the fuse is intended to interrupt at its rated capability. Therefore, fault currents up to the interrupting rating is the correct concept.