What is meant by Electrical Safety Fuse?

 A fuse is a safety device that gives overcurrent protection of an electrical circuit including the source of power and the load. There are various designs of fuse but basically it consists of a conductor that breaks once it is subjected to such overcurrent. It then needs to be replaced or rewired depending on the design. It is indeed an automatic way of removing power from faulty system (it is sometimes referred to as Automatic Disconnection of Supply, ADS).

Some of the characteristics of a fuse include;

Speed. It is the speed with which the fuse element breaks, this depends on how much current flows through it and the material from which the fuse element was made.

Rated Current. The maximum current that the fuse can retain.

I²t Value. This is the amount of energy that passes through the fuse element once it clears the electrical fault. The various values of I²t is usually provided in the manufacturers data sheet (if you can get that). The Melting I²t value is usually the amount of energy required to start melting the fuse element. The clearing I²t value is the total energy that passes through the fuse element when clearing a fault.

Breaking Capacity. The Max current that can safely be interrupted by the fuse. It usually should be higher than the prospective short circuit current. For small circuit systems it should be ten times the system’s current (the system which it is to protect).   

Temperature rating. Usually one should be aware that temperature does influences the performance of a fuse. It might increase or decrease its current allowance.

Rated Voltage. It should be greater than or the same as the supposed open circuit voltage. In other words, the rated voltage of the fuse should be higher than the maximum voltage source it would have to disconnect.

Usually, the fuse ratings are marked on the cap or body of the fuse. Note that a fuse is similar in use but not exactly the same as a circuit breaker!