1. FUSES
MRIDUL SADAWARTI

2. INTRODUCTION
This presentation discuses about fuses, how it works, its design and how it will effects the electric circuits around us .

3. What is fuse?
In electrical and electronics engineering a fuse is a type of sacrificial overcurrent protection device.
Its essential component is a metallic strip which melts as excess current flows through it.

4. PACKAGES AND MATERIAL Fuse consist of two main parts: Fuse casing
Fuse elements
Fuse casing may be made up of:
Ceramics
Glass
Plastic
Molded mica laminates

5. Fuse element is made up of:
Tin
Lead
Zinc
Silver
Copper
Aluminium

6. FUSE- WORKING
A fuse has a metallic strip of small cross section area , mounted between a pair of electrical terminal.
The fuse is connected in series with the circuit through which all the current will pass.
In case of heavy current, fuse will melt. This will break the circuits and protect the electrical appliance.

7. CHARACTERISTIC PARAMETER
Rated current
Maximum current that a fuse can bear without interrupting the circuit .
Speed
speed at which fuse blows depends on the amount of current passing through it .
Based on speed blow can be of 3 types
Normal blow
Fast blow
Slow blow

8. I2t value
A measure of energy required to blow the fuse.
Voltage drop
Resistance changes as the fuse temperature varies , this will lead to voltage drop .
temperature derating
With change of temperature , there’s a change in the nature of fuse .

9. Cut off characteristic

10. Prospective current
It is current which would have flown in the circuits if fuse had been absent .
Pre arcing time(Ts)
Time taken from the instant of increase to the instant of cut off and arc initiation.
Arcing time(Tl)
Time from the instant of cut off to the instant of arc being extinguished.
Total operating time
T=Ts+Tl
been absebt

11. Types of fuses Rewirable type Open type Semi closed type
Following are two main type of fuses:
Rewirable type
Cartridge type
Rewirable type
Open type
Semi closed type
Cartridge type
D type cartridge fuse
High rupturing capacity cartridge fuse

12. FUSE MARKINGS
Most fuses are marked on the body or on the end caps , with marking representing their rated value.
Fuse marking will convey the following information:
Ampere rating
Voltage rating
Breaking capacity
Time current characteristic
Approval by international standard agencies

13. Coordination of fuses in series
All fuses are connected in series at various level of power distribution system.
It will blow the fuse nearest to the fault.
In this case only faulty circuit is interrupted with minimal disturbance to the other circuits.