Fuse
A fuse is an overcurrent protective device containing a calibrated element that melts and opens the circuit when current exceeds a specified value for a sufficient time. Current-limiting fuses interrupt high fault currents within the first half-cycle, limiting let-through energy (I²t) and peak current. Low-voltage fuses are classified by utilisation category, such as gG for general-purpose cable protection, aM for back-up protection of motor circuits, and aR or gR for semiconductor protection. They are used in distribution boards, motor feeders, drives and control circuits. Selection parameters include rated voltage, rated current, breaking capacity, time-current characteristic, I²t value, physical size and holder or base type. Low-voltage fuses are covered by the IEC 60269 series, and high-voltage current-limiting fuses by IEC 60282-1.
Examples
- gG NH fuse protecting a distribution feeder
- aR semiconductor fuse protecting a drive rectifier
- Miniature cartridge fuse in a control circuit