The fuse is a device used in an electrical circuit for protecting electrical devices against overloads and short circuit. It is the simplest and cheapest devices used for interrupting an electrical circuit under short circuit or excessive overload current magnitudes.
It is used for overload or short circuit protection in high voltage up to 66 KV and low voltage up to 400 kV. In some places, their use is restricted to those applications where their performance characteristics are especially suitable for the current interruption.
The working of the fuse depends on the heating effect of the current. In normal operating condition, the normal current passes through the fuse. The heat develops in the fuse element because of the normal current and this heat is dissipated by the help of the surrounding air. Thus, the temperature of the fuse is kept below the melting point.
When the fault occurs the short circuit current passes through the fuse element. The magnitude of the current is much high as compared to the normal current. The short circuit current generates excessive heat in the fuse element. Thereby, the element becomes melts and break. The fuse protects the machine or apparatus from short circuit or overload current.
The fuse element is made of the highly selected metal conductor. The cartridge holds the fuse element. The main function of the fuse of the element is to allow the normal current to flows through the fuse and break the circuit when the high magnitude current passes through it.
Advantages of an Electrical Fuse
- It is the cheapest form of protection, and it does need any maintenance.
- Its operation is completely automatic and requires less time as compared to circuit breakers.
- The smaller sizes of fuse element impose a current limiting effect under short-circuit conditions.
- Its inverse time-current characteristic enables its use for overload protection.
Disadvantages of an Electrical Fuse
- Considerable time is required in replacing a fuse after the operation.
- The current-time characteristic of a fuse cannot always be correlated with that of the protective device.
Fuses are used for the protection of the cables in low voltages light, and power circuits and for transformers of rating not exceeding 200 KVA, in the primary distribution system. Fuses are used in low and moderate voltage applications where the frequent operation is not expected or where the use of a circuit breaker is uneconomical.