Eddy currents are loops of electrical current induced within conductors by a changing magnetic field in the conductor, due to Faraday's law of induction. Eddy currents flow in closed loops within conductors, in planes perpendicular to the magnetic field. The magnitude of the current in a given loop is proportional to the strength of the magnetic field, the area of the loop, and the rate of change of flux, and inversely proportional to the resistivity of the material.

2. CONTENT
 INTRODUCTION
 NEED OF EDDY CURRENT BRAKING SYSTEM
 OBJECTIVE
 EDDY CURRENT PRINCIPLE
 TIME CONTANT EQUATION
 CONSTRUCTION
 BASIC ELEMENTS REQUIRED
 THINGS DONE TILL NOW
 DC MOTOR
 SHAFT DESIGN
 LITERATURE REVIEWS
 ADVANTAGES
 DISADVANTAGES
 TILL NOW APPLICATIONS
 PREPERATIONS DONE FROM OCT TO DEC
 FUTURE PLANNING
 APPX. COST MODEL
 REFERENCES

3. INTRODUCTION
 An eddy current brake, like a conventional friction brake, is a device used to
slow or stop a moving object by dissipating its kinetic energy as heat.
 the drag force in an eddy current brake is an electromagnetic force between
a magnet and a nearby conductive object in relative motion, due to eddy
currents induced in the conductor through electromagnetic induction.
 In an eddy current brake the magnetic field may be created by a permanent
magnet, or an electromagnet so the braking force can be turned on and off or
varied by varying the electric current in the electromagnet's windings

4. NEED OF EDDY CURRENT BRAKING
SYSTEM
 When you have to brake quickly, the only thing that comes between safe stopping and
disaster is the simple science of friction: you slow to a halt when two surfaces rub
together
 Friction brakes have a big drawback too: every time you use them, they wear out a
little bit, and that means they're relatively expensive and there coefficient of friction
decreases with time, hence possible chance of accident.
 One option is to slow things down with the force of electromagnetism instead of
friction

5. OBJECTIVE
 Design of Eddy current braking system(Circular type)
 Generation of eddy current in Conductive, Non-Magnetic Material, using permanent
magnets and rotation using dc motor.
 Analysis of load on shaft due to circular disk.
 Use of belt pulley system to transmit power to shaft, hence study the same.
 Use of Radial thrust bearing to support shaft, hence study the same.

6. EDDY CURRENT PRINCIPLE
 Eddy currents are loops of electrical current induced within conductors by a
changing magnetic field in the conductor, due to Faraday's law of induction. Eddy
currents flow in closed loops within conductors, in planes perpendicular to the magnetic
field. They can be induced within nearby stationary conductors by a time-varying
magnetic field created by an AC electromagnet or transformer, for example, or by
relative motion between a magnet and a nearby conductor.
 The magnitude of the current in a given loop is proportional to the strength of the
magnetic field, the area of the loop, and the rate of change of flux, and inversely
proportional to the resistivity of the material

7. TIME CONSTANT EQUATION
τ = 2𝜌r^2/σD^2B^2
ρ= density of material
σ= specific conductivity
r= depth of disk/2
D= diameter of magnet exposure
B= magnetic field

9. BASIC ELEMENTS REQUIRED(In Our
Design)
 Dc motor(to rotate shaft)
 Shaft (to carry circular disk)
 Power transfer system (using belt pulley drive)
 Aluminium or copper disk(non magnetic and conductive, to generate eddy current)
 Permanent magnets( to generate Lorentz force)
 Base or stand(to support the system)
 Thrust Bearings (so that shaft could rotate freely)
 Dc battery(to run dc motor)

10. THINGS DONE TILL NOW
 Study of eddy current phenomena, and control their generation.
 Detailed analysis of how to generate eddy current in copper and aluminium circular
disk.
 Study of dc motors, and principle behind their working.
 Study on how to design shaft based on strength.
 Viewed, analysed and studied previous models and prototypes of electromagnet,
friction and eddy current braking system

11. DC MOTOR
 A DC motor is any of a class of rotary electrical machines that converts direct
current electrical power into mechanical power.
 Permanent magnet stators:- A PM motor does not have a field winding on the
stator frame, instead relying on PMs to provide the magnetic field against
which the rotor field interacts to produce torque. Compensating windings in
series with the armature may be used on large motors to improve
commutation under load. Because this field is fixed, it cannot be adjusted for
speed control.

12. SHAFT
 Shaft is a common and important machine element. It is a rotating member,
in general, has a circular cross-section and is used to transmit power. The
shaft may be hollow or solid. The shaft is supported on bearings and it rotates
a set of gears or pulleys for the purpose of power transmission. The shaft is
generally acted upon by bending moment, torsion and axial force. Design of
shaft primarily involves in determining stresses at critical point in the shaft
that is arising due to aforementioned loading.
 Design based on Strength :-In this method, design is carried out so that stress
at any location of the shaft should not exceed the material yield stress.
However, no consideration for shaft deflection and shaft twist is included.
 Basic stress equations :
 Bending stress
 Where,
M : Bending moment at the point of interest
do : Outer diameter of the shaft

13.  Maximum shear stress theory : Design of the shaft mostly uses maximum
shear stress theory. It states that a machine member fails when the maximum
shear stress at a point exceeds the maximum allowable shear stress for the
shaft material.

14. LITERATURE REVIEWS
 Mcconnell, H.M., ‘‘Eddy-current phenomena in ferromagnetic material,’’AIEE
Transactions, Vol. 73, part I, pp. 226–234, July, 1954.
 Gagarin, G., Kroger, U. and Saunweber, E., ‘‘Eddy-current magnetic track brakes for
high speed trains,’’ Joint ASME/IEEE/AAR Railroad Conference, pp. 95–99, 1987.
 “Effective magnetic properties of a composite material with circular conductive
elements ”,M. Gorkunov1;a, M. Lapine1, E. Shamonina2, and K.H. Ringhofer,
Published online 31 July 2002 The European journal of physics .
 The Design Of Eddy-Current Magnet Brakes ,Der-Ming Ma, Jaw-Kuen Shiau
“Department of Aerospace Engineering, Tamkang University, Danshuei, Taiwan 25137,
Republic of China” Received December 2009, Accepted December 2010 No. 09-
CSME-73, E.I.C. Accession 3159.

15.  International Journal of Innovative Research in Science, Engineering and Technology
An ISO 3297: 2007 Certified Organization Volume 3, Special Issue 2, April 2014
“Innovative Electro Magnetic Braking System” Sevvel, Nirmal Kannan , Mars Mukesh

16. PATENTS
 “ EP0497329” which is an eddy current drum brake. When you want to engage this
break you rotate permanent magnets so that their magnetic fields are pointed outward
through the conductive drum to produce eddy currents. When you want to turn the
break off you rotate the magnets so that their magnetic fields go in a circle instead of
going out through the break drum.
 The second patent is US patent “6,659,237”. This patent controls the strength of the
eddy current breaking by moving the magnets closer or further apart.

17. ADVANTAGES
 Quiet
 Wear less
 Noiseless
 No smell or pollution
 Cheap(80% less than friction brakes)
 Little or no Maintenance

18. DISADVANTAGES
 Interferes with the train signal equipment
 Takes times to completely stop vehicle
 Unstable at low speed

19. TILL NOW APPLICATION OR USES
 Roller-coaster
 Some versions of the German Inter City Express (ICE) train
 Japanese Shinkansen ("bullet train")
 French TGV
 Machines, such as circular saws and other power equipment
 Things like rowing machines and gym machines to apply extra resistance to the moving
parts so your muscles have to work harder.

20. PREPERATIONS DONE FROM OCT TO DEC
 October:- Studied eddy current generation, principle and previous models.
 November:- study of shaft and belt pulley drive system.
 December: Studied dc motor and dc battery.

21. FUTURE PLANNINGS
 Assemble of parts and accessories brought to form a working model, performing
braking, using eddy current.
 Analysis of force and load on shaft, due to circular disk.
 Selection of axial thrust bearing based on load requirement.
 Establish relationship between magnet distance and inertia force of rotating disk.

22. APPX. COST MODEL

23. REFERENCES
 C. S. Maclatchy, P, Backman, L. Bogan (1993) "A quantitative magnetic braking
experiment", American Journal of Physics 61:1096
 G. Ireson & J. Twidle (2008) "Magnetic braking revisited: Activities for the
undergraduate laboratory", European Journal of Physics 29:745–51
 E. Simeu and D. Georges, “Modeling and control of an eddy current brake,” Control
Engineering Practise, vol. 4, no. 1, pp. 19–26, 1996.
 Drive Source International, INC
 http://www.explainthatstuff.com/eddycurrentbrakes.html
 Patent EP0497329
 US patent 6,659,237

24. THANK YOU