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Rural Technology

A Fuse is a safety device. It is connected in series with the circuit & protects the electrical apparatus & equipments from damage, when excess current flows. There are several types of Fuses used in electrical field, but the Kitkat type fuse is commonly used in domestic installation. While specifying fuses in general, their type, current capacity & working voltage also should be specified.

A fuse is a safety device used for the purpose of protecting a circuit against excess current. In the event of excessive current, the Fuse element melts & open up the circuit there by protecting it from damage. fig. 14 Electrician Trade Theory 1st Year.

The fuses can interrupt automatically a circuit with an over current in it for a fixed time. They are mainly used to against the short-circuits. They limit the peak value of the fault current.

Placement of fuses -

In electrical installations, the fuses are always connected into the live wires & never into the neutral nor the protective earth line.

Rewirable type fuse -

This type of Fuses are simple in construction & the initial cost as well as the renewl cost is very 10w. The fuse element will melt after approximately 2 minutes when carrying a current rating. Kitkat & Piano type of fuses are the example of rewirable fuses.

Construction of Kitkat & Piano type fuse -

These are mostly use in domestic installation. The fusebse consist of a porceilin or polycarbonate material plastics. Base having silvered heavy brass terminals. The incoming & outgoing positive wire is connected to these terminals. Inside the fuse, carrier two contact terminals are provided. Fuse camer is made up of porceilin or polycarbonate material. It has two brass fuse carrier terminals, having a screw for connecting a fuse element. (fig.) In modern type fuse, Base contact terminals are made of silver coated brass & fuse carrier also made of tined copper & having a silver fuse.

Fuse element -

Generally Fuse elements are made of tined copper wire.

Function / Working of fuse -

During normal operations fuse element acts as a conductor and it provides complete path of current. When a short circuit occurs the current flowing through fuse increases sharpely. This causes the heating of the fuse element. Fuse element has a low melting point so that it melts at a lower temperature than that of ordinary conductor, when the heat caused by the short circuit current reaches the melting point of the fuse element the element melts & opens the circuit.

Fuse Rating -

1. Always use a fuse wire of appriate capacity with respective current.
2. Always use single fuse wire.
3. Never connect multistrand wire as a Fuse.
4. Keep proper length of Fuse element.
5. Connect Fuse wire properly.
6. Do not use unrecommended metal wires i.e. G.I., Nichrome.</nowiki> 1] INTEXT QUESTIONS- a) Fill in the blanks-
1. A Fuse is a ______ device.
2. A Fuse is used for protecting a circuit against _________ .
3. _____ & ______ type of Fuses are the examples of rewirable Fuses.
4. Fuse rating is usually marked on ________.
5. Fuse are always connected ________. b) True of False-
1. In electrical installations Fuses are connected to the neutral.
2. Fuse is connected in series with the circuit.
3. Fuse carrier has two contact terminals.
4. Fuse rating is expressed in current carrying capacity.
5. Fuse connected on phase wire for safety & security.

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Rural Technology