A fuse is a safety device to preventing overloading and short-circuiting a current circuit. It consists of a short length of conducting metal, which melts at certain heat and thereby breaks the circuit. The fuse wire melts at comparatively low temperature. The simple principle of protection by fuse is that whenever some excessive current flows or a short circuit occurs, the fuse wire gets heated and melts resulting in breaking the circuit. The fuse must be included on phase wire. If the fuse is provided on neutral wire and short circuit occurs, in that case, the fuse will blow off. But the apparatus due to which the short circuit has occurred will remain connected to phase wire even after melting of fuse on neutral wire.
Kit-Kat Type Fuse Unit
This is commonly used in house wiring and power wiring up to 440 volts. It is made of porcelain in two parts
• Base unit
• Fuse Carrier.
The base unit is fixed with switchboard permanently. The fuse carrier is removable unit. The thin fuse wire is fixed in the removable part and held between two screws. The phase wire or incoming wire is inserted from one side of the porcelain base and connected to metal clip. The out going connection is taken from the other terminal in the porcelain base. The two terminals inside the base are connected by fuse wire, which is held in the fuse carrier. The fuse wire being a thin wire and the weakest portion, the circuit wire can easily be replaced if that fuse wire melts due to over-load or short-circuit.
| Kit –Kat Type fuse |
The cartridge type fuse unit being totally enclosed, it will not be possible to rewire it. When the fuse blows the whole unit will have to be replaced. This type of fuse is available for voltage up to 660 volts and current rating up to 800 amperes. The powder filled in the container provides good insulating path for the fuse. It is not very economical. It is sometimes used at 415 volts supply system
| Cartridge Type Fuse Unit |
H.R.C. cartridge fuses are used for heavy duty applications and these are specially designed for extremely rapid operations. H.R.C. fuses are also designed to dissipate rapid heat produced by arc formed at the time of blowing out. The space around the fuse element within the main body is filled with incombustible powder The rating of the H.R.C. fuses is much more accurate and as already mentioned .
| H.R.C. (High Rupturing Capacity) Fuse Unit |
