Glossary · Electrical engineering and control panels
Fuse
Also known as: Fuse link, Fuse element
German: Sicherung
In electrical engineering, a fuse is a protective device that interrupts a circuit by melting a fusible element when the current exceeds a specified value for a sufficient time, and must be replaced after operating.
- Control panels
In one sentence
A fuse interrupts a circuit by melting when current is too high for too long; it must be replaced after it has operated.
Example
The control transformer's secondary is protected by a 4 A slow-blow fuse in a fuse terminal block.
How it applies
- Engineering: Select rated current, voltage, breaking capacity and time-current characteristic (for example gG for general use, aM for motor circuits, fast or slow for electronics). Low-voltage fuses follow the IEC 60269 series; fuses used in North America have their own UL and CSA classes.
- Maintenance: Replace fuses only with the same type and rating; a higher rating removes protection. Find the cause of a blown fuse before replacing it.
- Documentation: Show fuse type and rating in the circuit diagram and parts list, and label fuse holders in the cabinet. Maintenance manuals should include the warning about correct replacement ratings.
Fuse vs. circuit breaker
A fuse is replaced after operating; a Circuit breaker is reset. Fuses offer high breaking capacity and strong current limitation at low cost; breakers offer convenience and switching capability.