What is a fuse?
A fuse is a protective device that is designed to protect an electrical power system from the harmful effects of over-currents (currents higher than the normal operating current).
Fuses are sacrificial in that they are generally good for one time use and are destroyed in the process of operating. The use of fuses in a circuit provides cheap insurance should there be an accidental or unintentional fault in the system wiring or components.
Fuses have many unique performance characteristics, such as:
Optimum Component Protection
Fuses reduce short circuit (fault) currents that flow to a low value by "current limitation". There is no need for complex short circuit calculations and no concerns about costly future upgrades due to system expansion with increased fault currents. Their compact size offers low cost over-current protection for the highest short circuit levels.
Fuses do not produce gas, flames, arcs or other materials when clearing any value of over-current up to the highest level of short circuit. In addition, the speed of operation on high short circuit currents limits significantly the flash hazard at the fault location.
No moving parts to wear out or become contaminated by dust, oil or corrosion and no nuisance tripping. If a fault occurs, the fuse immediately operates in its predetermined manner or co-ordinates with other circuit components. The cause of the fault is then ascertained, corrected and a new fuse fitted. Fuse replacement ensures protection is restored to its original state of integrity. It should be stressed that the time taken for the replacement is very small in relation to the fault correction.
Standardised fuse characteristics and a high degree of current limitation ensure that there is simple and effective co-ordination between fuses and with other devices.