swaminarayan college of engineering and technology topic: protection devices fuses prepared by:...
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Swaminarayan college of engineering and technology
•Topic: Protection Devices Fuses
• Prepared by: Prajapati Divy Guide By: Prajapati Anant Jigna
Parmar Shah Keyur patel parth soni Vishal
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Content•Operating principles of fuses•Inverse time/current characteristic of
fuses•Fuses used as fault current limiters•Fuses and fault loop impedance•Fuse selection
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Circuit Protection
•Fuses•Circuit breakers
Next lesson
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Fuses•Two Basic types
•Rewireable
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HRC Fuses(High Rupture Capacity)
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How Does A Fuse Work?•As current increases, fuse element heats
up•Becomes liquid, and falls away.•An arc forms between the ends.•The ends melt away, the arc becomes
longer.•Eventually the gap is so great that it is too
long for the arc. Current stops flowingH = I2t
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Definitions•Current Rating•Voltage Rating•Time-Current characteristics
The maximum current that a fuse can carry continuously without deterioration
The maximum voltage that the fuse can safely operate.
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Minimum fusing current
The minimum current that the fuse element will start to melt
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With multiple arc points the time to blow is faster
Standard HRC Fuse Element
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HRC Low Voltage
•High breaking capacity & energy limitation.
•Restriction of electro-mechanical stress on cables and busbars
•Reliable short circuit and back-up protection.
•Accurate discrimination.•Low over-current protection.•Non-deterioration due to no moving parts
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HRC Semiconductor Fuses
•Electronics are more sensitive than motors or cables
•Energy let through has to be a lot less.•Must be very fast & accurate in operation•Fusing elements are made of all silver, &
thinner than standard