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

ContentsIntroductionTheory Of OperationConstructional DetailsWorking PrincipleClassification of eddy current brakesAdvantages & LimitationsApplicationsConclusion

WHAT IS EDDY

CURRENT…

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.

Introduction(continued…)Braking action is made by varying the strength of the

magnetic field by means of control switch.

Constructional DetailsComponents:-1. Electromagnets(stationary)

Cast Iron CoreConducting (Copper) WireMounting bolts

2. Disc(rotator)Mild steelMachined from plates

FVLHSV

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

Principle involved

Lenz’s LawFaraday’s law of EM induction

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.

Working Principle

Electromagnets produce magnetic field from supplied current.

Change of magnetic flux (with time) induces eddy currents in conductor (disc)

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.

Classification of ECB

1) Electrically excited eddy current brakes i.e., by Electromagnets

2) Permanent magnet eddy current brakes

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.

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.

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

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

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.

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.

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.