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FY ELECTRICAL 1. FUSE AND MCB. Presented by :- HARDIK TEJANI (ID\_24) (ENROLLMENT\_115) KARTHIK MENON (ID\_22) (ENROLLMENT\_049) PRAYAG PANDYA (ID\_34) (ENROLLMENT\_059) SWAPNIL MARATHE (ID\_16) (ENROLLMENT\_047). ELEMENTS OF ELECTRICAL ENGINEERING. Certificate. This is to certify that.

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FY ELECTRICAL 1

FUSE AND MCB

Presented by :-

HARDIK TEJANI (ID_24) (ENROLLMENT_115)

KARTHIK MENON (ID_22) (ENROLLMENT_049)

PRAYAG PANDYA (ID_34) (ENROLLMENT_059)

SWAPNIL MARATHE (ID_16) (ENROLLMENT_047)

ELEMENTS OF ELECTRICAL ENGINEERING

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Certificate

This is to certify that

TEJANI HARDIK (130410109115)

MENON KARTHIK (130410109049)

PANDYA PRAYAG (130410109059)

SWAPNIL MARATHE (130410109047)

of Electrical Engineering Department has completed their Active Learning Assignment for the subject ELEMENTS OF ELECTRICAL ENGINEERING (2110005) for the term ending in December, 2013.

DATE: 26/11/2013

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Topics

Introduction to fuse

Construction of fuse

Types of fuse

Working of fuse

Introduction to mcb

Parts of mcb

Difference between mcb and fuse

concluding videos

need of fuse
NEED OF FUSE
  • In any electric installation, if the metallic part of the electric appliance such as the metallic frame, metal covering of cables etc. comes in direct contact with a live wire, the metal will begin to get charged since it is a good conductor of electricity .
  • If a person comes in contact with the metallic part then he will get a shock. so, to save the person from the shock we need fuse and mcb.
introduction of fuse
INTRODUCTION OF FUSE
  • The basic purpose of the fuse is to protect electrical appliance and is composed of an alloy which has a low melting point. A strip of this fuse is placed in series with the circuit.
  • The working principle is that if the current is in excess then the strip would melt and break the circuit.
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In electronics and electrical engineering, a fuse (from the French fuser, Italian fuso, "spindle") is a type of low resistance resistor that acts as a sacrificial device to provide over current protection, of either the load or source circuit.
  • Its essential component is a metal wire or strip that melts when too much current flows, which interrupts the circuit in which it is connected. Short circuit, overloading, mismatched loads or device failure are the prime reasons for excessive current.
construction of fuse
CONSTRUCTION OF FUSE
  • The main components of a standard fuse unit consist of the following items:
  • Metal fuse element
  • Set of contacts
  • Support body
  • Connection
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The fuse element is made of zinc, copper, silver, aluminum, or alloys to provide stable and predictable characteristics.
  • The fuse element may be surrounded by air, or by materials intended to speed the quenching of the arc. Silica sand or non-conducting liquids may be used.
  • The fuse also consists of other components like Trigger assembly spring , Heat absorber.
rewireable fuse
REWIREABLE FUSE

This kind of fuse is most commonly used in the case of domestic wiring and small scale usage. Another name for this type is the KIT-KAT type fuse. The main composition is of a porcelain base which holds the wires.

The main advantage of this type of fuse is that it is easy to install and also replace without risking any electrical injury.

When there is an over surge that causes the fuse element to blow off, you can replace it. A new fuse carrier is inserted in the base.

cartridge fuse
CARTRIDGE FUSE
  • In this type of fuse, we have a completely closed container and there are contacts (metal) on either side. The level of sub division in this case includes:
  • D type
  • Link Type

Link type fuses: In Link type, we further have a knife blade type and a bolted type.

D Type Fuses: This cannot be interchanged and comes with the following main components: fuse base and cap, adapter ring and the cartridge.

high voltage fuse
HIGH VOLTAGE FUSE
  • Fuses are used on power systems up to 115,000 volts AC. High-voltage fuses are used to protect instrument like transformers used for electricity metering, or for small power transformers where the expense of a circuit.
  • They are used in power supply networks and for distribution uses. The most frequent application is in transformer circuits, with further uses in motor circuits and capacitor banks.
  • High-power fuse means that these fuses can interrupt several kilo amperes. Some manufacturers have tested their fuses for up to 63 kA cut-off current.
working of fuse
WORKING OF FUSE
  • Fuse will melt when the current exceeds its maximum current rating. By melting , the fuse thus destroys a portion of the conducting path. This stops the current from flowing in the rest of the circuit.
  • When the fuse melt, the fuse element absorbs some energy. This energy is given by I2t where I is peak value of current interrupted and t is the time taken to clear the fault.
  • When the fuse blows , it gives an indication that there is some mal functioning in the circuit.
introduction of mcb
INTRODUCTION OF MCB
  • A  Miniature circuit breaker is a manually or automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit.
  • Its basic function is to detect a fault condition and interrupt current flow. 
  • Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation.
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Circuit breakers are made in varying sizes, from small devices that protect an individual household appliance up to large switchgear designed to protect high voltage circuits feeding an entire city.
symbol of mcb
SYMBOL OF MCB

Miniature circuit = switch + trip unit breaker (MCB)

dimension of mcb
DIMENSION OF MCB

44 maxi

21.3

81

35

45maxi

width

symmetrical

rail

external

part

depth

60

10 maxi

parts of miniature circuit breakers
PARTS OF MINIATURE CIRCUIT BREAKERS

A

C60N

NC100 / NC125

terminal

terminal

bimetral strip

fixed contact

movingcontact

strip braid

moving

contact

strip braid

magnetictrip

magnetic trip

strip braid

bimetal strip

load side terminal

load side terminal

some important parts of mcb
SOME IMPORTANT PARTS OF MCB
  • 1.Actuator lever - used to manually trip and reset the circuit breaker. Also indicates the status of the circuit breaker (On or Off/tripped).
  • 2.Actuator mechanism - forces the contacts together or apart.
  • 3.Contacts - Allow current when touching and break the current when moved apart.
  • 4.Terminals
  • 5.Bimetallic strip.
  • 6.Calibration screw - allows the manufacturer to precisely adjust the trip current of the device after assembly.
  • 7.Solenoid
  • 8.Arc divider/extinguisher
overload protection
OVERLOAD PROTECTION
  • Current Limiting Breakers use an electromechanical (Thermal /Magnetic) trip unit to open the breaker contacts during a over current event. The thermal trip unit is temperature sensitive and the magnetic trip unit is current sensitive. Both units act independently and mechanically with the breaker’s trip mechanism to open the breaker’s contacts.
  • MCB – miniature circuit breaker’s instantaneous trip unit interrupts a short circuit in 2.3 to 2.5 milliseconds, and stops the flow of current
thermal trip unit
Thermal Trip Unit
  • The thermal trip unit protects against a continuous overload. The thermal unit is comprised of a bimetal element located behind the circuit breaker trip bar and is part of the breaker’s current carrying path.
  • When there is an overload, the increased current f low heats the bimetal causing it to bend. As the bimetal bends it pulls the trip bar which opens the breaker’s contacts.
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The time required for the bimetal to bend and trip the breaker varies inversely with the current. Because of this, the tripping time becomes quicker as current increases in magnitude . Overload protection is applicable to any installation, conductor, or component which can be subjected to low-magnitude but longtime over currents
magnetic trip unit
Magnetic trip unit
  • The Magnetic trip unit protects against a short circuit.

The magnetic trip unit is comprised of an electromagnet and an armature. When there is a short circuit, a high magnitude of current passes through the coils creating a magnetic field that attracts the movable armature towards the fixed armature. The hammer trip is pushed against the movable contact and the contacts are opened. The opening of the breakers contacts during a short circuit is complete in .5 milli-seconds.

arc runners arc chutes
Arc runners / Arc chutes
  • The arc runner and arc chute limit and dissipate the arc energy during the interruption of an overload or short circuit event.
  • During an overload or short circuit event, the contacts of the breaker separate and an electrical arc is formed between the contacts through air.
  • The arc is moved into the arch chute by “running” the arc down the interior of the breaker along the arc runner. When the arc reaches the arc chute it is broken into small segmented arcs.
bibliography
BIBLIOGRAPHY
  • ELEMENTS OF ELECTRICAL ENGINEERING

(J.N SWAMY AND N.V SINHA)

  • INFORMATION FROM:-

WIKIPEDIA

ABBWORKS

  • PICTURES FROM :-

GOOGLE

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