Presented By :~ AMIT PATEL

Introduction

of eddy current. Introduction of eddy current brake. Types of eddy current brake. Circular eddy current brake. Linear eddy current brake. Working principle. Advantages and Disadvantages. Application and future aspects. conclusion

When a magnetic core ( or conductor ) is subjected to a time varying magnetic field , voltages are induced in all possible paths enclosing the flux. Voltage produces circulating currents in the core. These currents are known as eddy currents. These circulating eddies of current have inductance and thus induce magnetic flux.

It

slows an object by creating eddy currents . Braking action is made by varying the strength of the magnetic field. Braking force depends on speed of object. A braking force is possible when electric current is passed through the electromagnets.

Circular

eddy current

brakes Linear eddy current brakes

Brake

assembly is circular in shape. Consist of a disc (rotor) made up of magnetic material. Disc is placed between poles . Conductor coils are wound on poles to create magnetic field. The movement of the disc through the magnetic field of the electromagnets creates eddy currents in the discs.

The

principle of the linear eddy current brake has been described by the French physicist Foucault. The linear eddy current brake consists of a magnetic yoke with electrical coils positioned along the rail. This magnet does not touch the rail, but is held at a constant small distance from the rail (approximately 7 mm).

Eddy

current brake is based on two basic laws of electromagnetics , which are Faradays law

e = - d/dt Lenz

law :- An induced electromotive force (emf) always gives rise to a current whose magnetic field opposes the original change in magnetic flux

Magnetic field lines across the magnetic material inside a copper tube

Electromagnets produce magnetic field from supplied current . Due to change in magnetic flux linkage(with time) EMF is induced in conductor (disc). EMF produces eddy currents in disc. Eddy Currents produce another magnetic field opposing the first field. Opposing magnetic fields create force that reduces velocity.

(Arrangement of ECB in high speed trains)

V =0coil

Pole core

V>0 S F FB

NFRail

SA

N

F

N

A

Flux lines

The

braking energy of the vehicle is converted in eddy current losses which lead to a warming of the rail. Braking force is low at low speeds and high at high speeds. Copper and aluminum is used as winding materials. permanent magnets can be used instead of electromagnets , thus not requiring any power supply.

No

contact, therefore no wear or tear. No noise or smell. Adjustable brake force. High brake forces at high speeds. It uses electromagnetic force instead of friction. Can be activated at will via electrical signal. Low maintenance. Light weight.

Braking

force diminishes as speed diminishes. no ability to hold the load in position at standstill. ECB is used with ordinary mechanical brakes. very tough design and simulation.

In

high speed trains. In roller coaster for braking and smooth functioning. It is also used in vehicles but still not widely used.

In

future ordinary brakes will be replaced by the ECB completely. By the use of ECB in future we can control high speed train completely. By some new invention of extra mechanism we can use ECB for slow speed vehicles also.

ECB

is a good invention for the speed control of high speed vehicles We can control the speed of high speed vehicles without wear and tear . Drawback of ordinary mechanical braking system can be overcome by application of ECB. It makes use of opposing tendency of eddy current.

www.google.co.in www.explainthatstuff.com/eddy-current-

brakes www.wikipedia.org/wiki/Eddy_current_brak e/ www.wikipedia.org/wiki/Eddy_current