Properties of Fuses
Fuses have been around for a long time and found in all homes and work places. Though they are very old invention and have been used without any change in principle for a long time, yet they are as indispensable today as they were a hundred years before.
The current in any circuit can increase due to some fault in the appliance, such as a short circuit, or through overloading. Though overloading can also burn a motor or appliance, it is the short circuit current that is the highest, and fuses are very suitable for these types of over-current. They are the most common type of protection against short circuits taken in domestic circuits.
The old rewireable fuses are reusable, but can be a fire hazard as the arc does not go off quickly. In the sealed ceramic body or glass encased fuses, some compounds are filled inside the capsule that cater to fast arc quenching.
Fuses are of a very simple construction, are reliable and cheap, and therefore are inherently popular. However there is a disadvantage of fuses in that they are insensitive to small amounts of over-current. They will burn out, but only after a time long enough for the appliance to become damaged, and for this purpose additional protection like miniature circuit breakers have to be used.
The plus point in the favor of fuses is that they have a very fast speed of operation when high currents are involved and this is highly beneficial in case of short circuit over currents as they operate faster than circuit breakers.