WELCOMETO

SCIENCEPOWERPOINT

PRESENTATION2015-16

FormativeAssessment- 1

Activity-3Topic:

Fuse Wires, Structures And

Appliances

INTRODUCTION A fuse is one type of over current device that is designed to be a sacrificial element in an electrical power system. Fuses are designed to open circuits when excessive currents are present due to overloads

or faults and to prevent further damage to the system that might result if the fuse were not present. A fuse interrupts excessive current . so that further damage by overheating or fire is prevented threats to human life and property damage.

WHAT IS FUSE WIRE ?

A fuse wire is a strip of metal , constructed of copper, zinc, silver or aluminium . Some fuses are made of alloys of these metals. Some fuses use two strips with one designed to melt quickly to prevent a short circuit and another designed to fail in the event of a long-term overload. 

A FUSE WIRE IS MADE UP OF ? WHAT

A fuse wire is made up of alloy of lead or tin plated copper wire because of its low melting point and high resistance .It is the tendency of a fuse wire to become slightly warm during normal use, its surface would tend to oxidize and thus diminish its cross-section during ordinary service. Leading to premature and improper failure. So it is important to protect the surface of fuse wire against corrosion. 

STRUCTURE OF FUSE WIRE A fuse consists of a metal strip or wire fuse element, of small cross-section compared to the circuit conductors, mounted between a pair of electrical terminals, and enclosed by a non-combustible housing

The fuse is arranged in series  to carry all the current passing through the protected circuit. The resistance of the element generates heat due to the current flow

TYPES OF FUSE WIREFuses can be divided into two main categories according to the type of input supply voltage :AC fusesDC fusesFuses can also be categorized based on one

time or multiple Operations : One time use only fuse  Resettable fuses    Other types of fuses are- semi-conductor fuse  High voltage fuse             

There is a little difference between AC and DC Fuses used in the AC and DC Systems.In a DC system, when the metallic wire Melts because of the heat generated by the over current, then Arc is produced and it is very difficult to extinct this arc because of DC constant value. So in order to minimize the fuse arcing, DC fuse are little bigger than an AC fuse which increase the distance between the electrodes to reduce the arc in the Fuse. On the other hand, i.e. in the AC system, voltage with 60Hz or 50Hz frequency changes it amplitude from zero to 60 times every second, so arc can be extinct easily as compared to DC. Therefore, AC fuses are little bit small in sizes as compared to DC fuses.

AC AND DC FUSES

  One time use fuses contain a metallic wire, which burns out, when an over current, over load or mismatched load connect event occur, user has to manually replace these fuses, switch fuses are cheap and widely used in almost all the electronics and electrical systems. A polymeric positive temperature coefficient device commonly known as a resettable fuse is a passive electronic component used to protect against over current faults in electronic circuits.

ONE TIME USE ONLY FUSE AND RESETTABLE FUSES

SEMI- CONDUCTOR AND HIGH

VOLTAGE FUSE

Semiconductor fuses are used to protect against Over- current

conditions in semiconductor device.High voltage fuses are used to

protect instrument transformers used for electricity metering or for

small power transformers.

The primary reason for using a fuse is not to protect the device per se, but to prevent fire or other events from happening if the device malfunctions.  A fuse rated at a particular current is a bit of a misnomer. Notice that it takes time for something to heat and melt and if the rate of heating is proportional to the current, you can sustain a much higher current through fuse as long as you shorten the current's duration in time. . A fuse is a "current limiting device".

HOW FUSE PROTECT ELECTRICAL APPLIANCES

Finally, when picking the fuse you want something that will disrupt the circuit when it's obviously beyond the designed operating current that takes the mentioned variables into consideration and definitely doesn't disrupt the circuit when it's operating as designed. The way a traditional single use fuse works is by using a small piece of wire who's resistance is such that the wire will heat and melt at a predetermined current. It is designed to be a cheap, expendable "weakest-link" which upon failure will open the circuit preventing further damage or fire risk.

CONCLUSION from the above slides we came to know many things about the fuse wires. They help in short circuit protection. They are regarded as Environmental friendly technology.They are very essential in electrical appliances.

PREPARED BY:

PREETI SMITA SAMAL

ANANYA TRIPATHYB.MUKTA TANAYA

MAHAK CHOUDHURY

DIKSHA GUPTA

GUIDED BY:MR.BHAKTI BINOD

THANK YOU