Download - A presentation on "EDDY CURRENT BRAKES"
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A Presentation onEDDY CURRENT BRAKES
Presented By:Ashutosh Polakhare
Seat No. T120212551
AISSMS COLLEGE OF ENGINEERING
Department of Electrical Engineering
Guided By:Mrs. V.N.Tarange
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ContentsIntroductionTheory Of OperationConstructional DetailsWorking PrincipleClassification of eddy current brakesAdvantages & LimitationsApplicationsConclusion
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WHAT IS EDDY
CURRENT…
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IntroductionEddy current is a swirling current set
up in a conductor in response to a changing magnetic field.
By Lenz's law, the current swirls in such a way as to create a magnetic field opposing the change
It slow an object by creating eddy
currents through electromagnetic induction which create resistance, and in turn either heat or electricity.
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Introduction(continued…)Braking action is made by varying the strength of the
magnetic field by means of control switch.
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Constructional DetailsComponents:-1. Electromagnets(stationary)
Cast Iron CoreConducting (Copper) WireMounting bolts
2. Disc(rotator)Mild steelMachined from plates
FVLHSV
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It consists of two members, a stationary magnetic field system and a solid rotary member, generally of mild steel.
Two members are separated by a short air gap, they're being no contact between the two for the purpose of torque transmission.
Stator consists of pole core, pole shoe, and field winding.Pole core and pole shoes are made of cast steel and fixed to the
state of frames by means of screw, bolts, rivets.Max. diameter: 1.The spacing of vehicle chassis frame 2.Vehicle floor clearance
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Principle involved
Lenz’s LawFaraday’s law of EM induction
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Theory of operation Induced EMF is proportional to
the strength of magnetic field & speed of conductor.
The direction of the current is in such a way as to oppose the cause, i.e. movement of the disc.
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Working Principle
Electromagnets produce magnetic field from supplied current.
Change of magnetic flux (with time) induces eddy currents in conductor (disc)
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Eddy Currents produce another magnetic field opposing first field.
Opposing magnetic fields create force that reduces velocity
A control switch is put on which is placed on the steering column in a position for easy operation.
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Classification of ECB
1) Electrically excited eddy current brakes i.e., by Electromagnets
2) Permanent magnet eddy current brakes
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Electrically excited eddy current brakes It consists of a magnetic yoke with electrical coils which are being magnetized
alternately with current .When the magnet is moved along the rail, it generates a non-stationary
magnetic field which generates electrical tension and causes eddy currents. These disturb the magnetic field in such a way that the magnetic force is
diverted to the opposite of the direction of the movement.The braking energy of the vehicle is converted in eddy current losses which
lead to a warming of the rail.
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Permanent magnet eddy current brakes
Permanent magnet ECB are a simple & reliable alternative to mechanical & electromagnetic brakes.
These brakes need a mechanical actuator to turn the magnets in an on and off position.
Permanent ECB have been developed for subways, trams and local trains.
The main advantage of this type of brake is safety i.e., it does not need electrical power supply to energize the magnet.
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1) It uses electromagnetic force and not friction.2) No contact, therefore no wear or tear.3) High brake forces at high speeds.4) Long Life5) Low maintenance6) Operates at any rotational speed7) Light weight
Advantages
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Limitations
1) Braking force diminishes as speed diminishes with no ability to hold the load in position at standstill.
2) Need of electric power3) It can not be used at low speed vehicles or vehicle
running at low speed
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Applications1) It is used as a stopping mechanism in trains.2) For high speed passenger and goods vehicle3) It is also used in the smooth breaking and functioning
of roller coasters and such fast moving machines.
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ConclusionECB is a good invention for the speed control of high
speed vehiclesWe can control the speed of high speed vehicles
without wear and tear in parts of it.Drawback of ordinary mechanical braking system can
be overcome by application of ECB.
It makes use of opposing tendency of eddy current.
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ReferencesManual 1 Gonzalez, Volume 25,Issue 4,July 2004IEEE Transactions on magnetics, Volume 34, Issue 4, July
1998Analysis of eddy current brake for high-speed railway by
Wang.P.J. & Chiuch.S.J. Automobile electrical equipments by Young & Griffith.Automatic engineering by Kripal Sing.Eddy Current Brakes for Haptic Interfaces, Design,
Identification,and ControlClutches and brakes by William.C.Orthwin.
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