In this topic, you study Electrical Fuse – Definition, Construction, Types & Diagram.
An electrical circuit must be safeguarded against the harmful effects of excessive currents. These excessive currents may be because of overloading or short-circuit faults. When an electrical motor is overloaded, it draws an excessive current. If proper precautions are not taken, this excessive current results in the overheating of the motor which ultimately leads to its damage. In case of domestic installation, short circuiting takes place when there is direct connection between the live and neutral conductor. Under these circumstances, the resistance to the supply being very low, enormous current will flow through the conductors. Such a high current leads to an excessive heat rise which, if adjacent to inflammable materials will almost certainly cause an outbreak of fire. In all such cases, therefore, it is necessary to interrupt these excessive currents before they cause any damage. Fuse is the simplest current interrupting device for the protection against excessive currents.
General Construction of the Electrical Fuse
In general, the fuse consists of a small piece of metal connected in between two terminals mounted on the insulated base.
Function of the Electrical Fuse
When the fuse is inserted in a circuit to be protected, it carries the normal working current safely without heating. But when the current exceeds the predetermined value, it melts due to its rapid overheating. The circuit is then interrupted thereby preventing any damage due to excessive current. Thus, the fuse is in effect a safety valve for the electrical circuit.
Types of Electrical Fuse
Following two types of fuses are commonly used in practice :
- Semi-enclosed or rewirable type,
- High rupturing capacity (H.R.C.) cartridge type.