Fuse characteristics

plotting fuse characteristics in MALAB

1. FUSE CHARACTERISTICS

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DEPARTMENT OF ELECTRICAL AND ELECTRONICS


ABSTRACT:
In electronics and electrical engineering, a fuse is an electrical safety device that operates to
provide overcurrent protection of an electrical circuit. Its essential component is a metal wire
or strip that melts when too much current flows through it, thereby interrupting the current.
The time and current operating characteristics of fuse are obtained for different ampere
ratings of fuse, to provide adequate protection without needless interruption.

2. FUSE CHARACTERISTICS

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DEPARTMENT OF ELECTRICAL AND ELECTRONICS


SL NO TITTLE PAGE NO
01 INTRODUCTION 03
02 EXPERIMENTAL DETAILS, PRECAUTIONS , CIRCUIT
DIAGRAM
05
03 NATURE OF GRAPH, EXPERIMENTAL PROCEDURE 06
04 TABULAR COLUMN 07
05 GRAPH OBTAINED FROM EXPERIMENT 08
06 CONCLUSION 09
07 REFERENCE

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3. FUSE CHARACTERISTICS

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DEPARTMENT OF ELECTRICAL AND ELECTRONICS

INTRODUCTION:
The fuse was invented by the scientist Edison in the year 1880. It is a simple protective
devise which works on the principle of current interruption, if current through it becomes
excessive. Hence it protects the equipment from effect of excessive high currents such as
overheating, short circuiting, firing, damages etc.
The fuse wire is always connected in series with circuit or appliance to be protected. A
small piece of metal used in fuse is called Fusing element. It carries normal working current
safely but melts due to excessive currents under abnormal conditions it is due to heat
produced in fusing element by excessive current so melting point of fuse plays important role
in design of fuse.
Some of the fusing elements with their melting point and specific resistance.
Metals Melting point in
0
c Specific resistance in µΩ-cm
Aluminium 658.7 2.86
Copper 1084 1.75
Lead 327 21.0
Silver 960.5 1.64

The desirable characteristics of any fuse element are
1. Low melting point
2. High conductivity
3. Free from deterioration due to oxidation
4. Low cost
For small value of currents lead-tin alloy is used for making the fuse element. The most
preferred lead-tin alloy consists of 37% of lead and 63% of tin.
For large values of current copper or silver is used for making fuse element.The lead-tin alloy
is not used because after fusing there is excessive metal released in case of alloy as diameters
of such wires are large.

4. FUSE CHARACTERISTICS

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DEPARTMENT OF ELECTRICAL AND ELECTRONICS

The electrical conductivity of copper is second only to silver. The conductivity of Copper is
97% that of silver. Due to its much lower cost and greater abundance, copper has traditionally
been the standard material used for electricity transmission applications.
Properties of copper
 Tensile strength.
 Ductility.
 Strength and ductility combination.
 Creep resistance.
 Corrosion resistance.
 Coefficient of thermal expansion.
 Thermal conductivity.
 Solderabilit

Advantages
 Excellent heat conductivity.
 Excellent electrical conductivity.
 Good corrosion resistance.
 Good biofouling resistance.
 Good machinability.
 Retention of mechanical and electrical properties at cryogenic temperatures.
 Non-magnetic.
Disadvantages
As with most anything, there are disadvantages to copper and these include the following:
 It is easily scratched
 Easily loses its colour due to heating
 It is costly
Applications of copper
 For making electrical parts
 Heat exchangers
 For making various copper alloys, such as brass and bronze
 For household utensils etc

5. FUSE CHARACTERISTICS

5
DEPARTMENT OF ELECTRICAL AND ELECTRONICS


EXPERIMENTAL DETAILS :
To determine the current characteristics of the given fuse wires for different ampere ratings.

PRECAUTIONS:
1. Before starting the experiment note down the specification of fuse wire.
2. Keep load switch in off position dimmer at zero position and switch on the board in
closed position.

CIRCUIT DIAGRAM:

6. FUSE CHARACTERISTICS

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DEPARTMENT OF ELECTRICAL AND ELECTRONICS

NATURE OF GRAPH :









EXPERIMENTAL PROCEDURE:
1. We made the connections as per the circuit diagram.
2. We kept auto transformer to its zero position and applied 90% of load.
3. We kept switch to its OFF position and connected fuse wire (5A) across certain length
(say 5cm).
4. Then supply is given through the auto transformer and varied it, till fuse wire melts.
Now circuit is in open condition.
5. We closed the circuit by making switch ON position and noted down the ammeter
reading and switched OFF the supply and reconnected the fuse wire.
6. Then supply is given through the auto transformer by keeping switch in ON position
in such way that current flowing through the circuit is slightly reduced current
compare to the noted current.
7. Now we simultaneously switched OFF the switch and started the timer and noted the
time taken by the fuse to melt.
8. This procedure is repeated for some more readings and plotted the graph.
9. This whole procedure is repeated for different ampere rating of fuse wire (10A, 15A).

7. FUSE CHARACTERISTICS

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DEPARTMENT OF ELECTRICAL AND ELECTRONICS


TABULAR COLUMN
(1) For fuse ampere rating of 5A and length of fuse wire is 5cm
SL . NO TIMR FOR FUSING(SEC) FUSING CURRENT(AMPS)
1 298 4.8
2 136 4.9
3 53 5.0
4 13 5.1
5 9 5.2
6 3 5.3


(2) For fuse ampere rating of 10A and length of fuse wire is 5cm
SL . NO TIMR FOR FUSING(SEC) FUSING CURRENT(AMPS)
1 292 9.2
2 250 9.4
3 152 9.6
4 100 9.8

8. FUSE CHARACTERISTICS

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DEPARTMENT OF ELECTRICAL AND ELECTRONICS


(3) For fuse ampere rating of 15A and length of fuse wire is 5cm
SL . NO TIMR FOR FUSING(SEC) FUSING CURRENT(AMPS)
1 7 14.8
2 60 14


GRAPH OBTAINED FROM EXPERIMENT :

9. FUSE CHARACTERISTICS

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DEPARTMENT OF ELECTRICAL AND ELECTRONICS



CONCLUSION:
 We observed that, for 5A,10A and 15A fuse wire ,the fuse has inverse time-current
characteristics. i.e as the magnitude of fault current is higher, smaller is time taken by
the fuse to melt. When fault current is low, the time taken by the fuse is more.

10. FUSE CHARACTERISTICS

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DEPARTMENT OF ELECTRICAL AND ELECTRONICS




REFERENCE:
 ‘Switchgear and Projection’ by Uday A Bakshi and Mayuresh V Bakshi.
 Relay and high voltage lab manual.
 https://en.wikipedia.org/wiki/Copper_conductor
 Matlab for engineers, Moore 4
th
edition page no-167, magnitude plotting.
 http://copperalliance.org.uk/education-and-careers/education-resources/copper-
properties-and-applications
 https://www.slideshare.net/amsmetal/the-advantages-of-copper


GRAPH 4
x1= [298 136 53 13 9 3 ]
y1= [4.8 4.9 5.0 5.1 5.2 5.3]
figure;plot(x1,y1)
title('time current characteristics' ),xlabel('time in
seconds'),ylabel('current in ampere' )
x2=[292 250 152 100]
y2=[9.2 9.4 9.6 9.8]
hold on;plot(x2,y2,'r'); hold off;
x3=[7 60]
y3=[14.8 14]
hold on;plot(x3,y3,'g');hold off;
legend('5A','10A','15A')


all 3 graphs
x1= [298 136 53 13 9 3 ]
y1= [4.8 4.9 5.0 5.1 5.2 5.3]
figure;plot(x1,y1)
title('time current characteristics' ),xlabel('time in
seconds'),ylabel('current in ampere' )
x2=[292 250 152 100]
y2=[9.2 9.4 9.6 9.8]
hold on;plot(x2,y2,'r'); hold off;
x3=[7 60]
y3=[14.8 14]
hold on;plot(x3,y3,'g');hold off;
legend('5A','10A','15A')
figure; subplot(1,3,1);plot(x1,y1)
subplot(1,3,2);plot(x2,y2, 'r')
subplot(1,3,3);plot(x3,y3, 'g')
title('time current characteristics' )
title('15A')

11. FUSE CHARACTERISTICS

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DEPARTMENT OF ELECTRICAL AND ELECTRONICS

subplot(132);title( '10A')
subplot(131);title( '5A')

final
x1= [298 136 53 13 9 3 ]
y1= [4.8 4.9 5.0 5.1 5.2 5.3]
figure;plot(x1,y1)
title('time current characteristics' ),xlabel('time in
seconds'),ylabel('current in ampere' )
x2=[292 250 152 100]
y2=[9.2 9.4 9.6 9.8]
hold on;plot(x2,y2,'r'); hold off;
x3=[7 60]
y3=[14.8 14]
hold on;plot(x3,y3,'g');hold off;
legend('5A','10A','15A')
figure; subplot(1,3,1);plot(x1,y1)
subplot(1,3,2);plot(x2,y2, 'r')
subplot(1,3,3);plot(x3,y3,'g')
title('time current characteristics' )
title('15A')
subplot(132);title( '10A')
subplot(131);title( '5A')