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

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

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

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.

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

TIME CONSTANT EQUATIONr^2/σD^2B^2ρ= density of materialσ= specific conductivityr= depth of disk/2D= diameter of magnet exposureB= magnetic field

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)

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

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.

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

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.

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.

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

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.

ADVANTAGES

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

DISADVANTAGES

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

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.

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.

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.

APPX. COST MODEL

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

THANK YOU