EDDY CURRENT BRAKE

CONTENTS :~ Introduction of eddy

current Introduction of eddy

current brake Components And

Operational Features Of Eddy Current Brakes

How eddy current brake works?

Advantages Disadvantages Applications conclusion

INTRODUCTION OF EDDY CURRENT

Eddy currents are electric currents induced in conductors when exposed to a changing magnetic field; due to relative motion of the field source and conductor or due to variations of the field with time.

This can cause a circulating flow of electrons, or current, within the body of the conductor.

These circulating eddies of current have inductance and thus induce magnetic fields. 

� Eddy current brakes, like conventional friction brakes, are responsible for slowing an object, such as rotating machinery, a moving train, or even a roller coaster.These brakes make use of opposing tendency of eddy currents. The drawbacks of ordinary brakes which uses mechanical blocking could be eliminated by use of a more simple and effective mechanism known as eddy current brakes.

� There are two basic types: (1)circular

(2)linear

Introduction Of Eddy Current Brake

Circular Eddy Current Brakes:-

Linear Eddy Current Brakes:-

Electromagnets Cast Iron Core Conducting (Copper) Wire Mounting bolts Disc Mild steel machined from plates

Essentially the eddy current brake consists of two parts, a stationary magnetic field system and a solid rotating part, which include a metal disc.

Two members are separated by a short air gap, they're being no contact between the two for the purpose of torque transmission. Consequently there is no wear as in friction brake.

COMPONENTS AND CONSTRUCTIONAL

FEATURES OF EDDY CURRENT BRAKES:-

Stator consists of pole core, pole shoe, and field winding.

The field winding is wounded on the pole core. Pole core and pole shoes are made of east steel laminations and fixed to the state of frames by means of screw or bolts.

Copper and aluminum is used as winding materials.During braking, the metal disc is exposed to a magnetic field from an electromagnet, generating eddy currents in the disc. The magnetic interaction between the applied field and the eddy currents slow down the rotating disc. Thus the wheels of the vehicle also slow down since the wheels are directly coupled to the disc of the eddy current brake, thus producing smooth stopping motion.

Working Principle

HOW DOES AN EDDY CURRENT BRAKE STOP SOMETHING MOVING?

Suppose we have a huge solid block of copper mounted on wheels. It is moving at a very high speed and we need to stop it.

Suppose we place a giant magnet next to the track so that train had to pass nearby.

As the copper approached the magnet eddy currents would be generated inside the copper which would their own magnetic field.

As the front passed by, slowing down, the currents there would reverse, generating an attractive magnetic field that tried to pull the train back again. (again, slowing it down).

The copper would heat up the eddy currents swirled inside it, gaining the kinetic energy lost by the train as it slowed down.

As the front part approached the magnet eddy currents in that bit of copper would try to generate a repulsive magnetic field to slow down copper’s approach to magnet.

ARRANGEMENT OF DIFFERENT PARTS IN EDDY CURRENT BRAKE

(Arrangement of ECB in high speed trains)

Advantages Of Eddy Current Brakes:-

• It uses electromagnetic force and not mechanical friction • Non-mechanical (no moving parts, no friction)• Fully resettable• Can be activated at will via electrical signal• Low maintenance• Operates at any rotational speed• Light weight• Eddy-current brakes are quiet, frictionless, and wear-free,

and require little or no maintenance. • They produce no smell or pollution (unlike friction brakes,

which can release toxic chemicals into the environment).

All this makes them much more attractive than noisy friction brakes that need regular inspection and routinely wear out. It's been estimated that switching an electric train from friction brakes to eddy-current brakes could halve the cost of brake operation and maintenance over its lifetime.

DISADVANTAGES:- Braking force diminishes as speed diminishes with no

ability to hold the load in position at standstill.

 That could be considered to be a safety issue, but it really means that friction braking may need to be used as well.

Eddy-current brakes can only be used where the infrastructure has been modified to accept them.

It can not be used at low speed vehicles or vehicle running at low speed

Applications:- For additional safety on long decants in mountain area  For high speed passenger and goods vehicle.

Eddy current brakes are best substitutes for ordinary brakes, which are being used nowadays in road vehicles even in trains, because of their jerk-free operation.

In mountain areas where continuous braking force is needed, for a long time, the eddy current braking is very much useful for working without overheating.

Eddy current brakes are very much useful for high-speed passengers and good vehicles.

It can also be used to slow down the trolleys of faster roller coasters.

There are a number of major commercial applications of eddy current brake technology in the mining, railroad, and elevator industries.

We'll also find eddy current brakes in all kinds of machines, such as circular saws and other power equipment. And they're used in things like rowing machines and gym machines to apply extra resistance to the moving parts so your muscles have to work harder.

Conclusion:-

The ordinary brakes which are being used now a days stop the vehicle by means of mechanical blocking. This may cause skidding and wear and tear of the vehicle.

And if the speed of the vehicle is very high the brake could not provide that much high braking force and it will cause problems.

These drawbacks can be eliminated by using a simple and effective mechanism of braking system called eddy current brakes.

It is an abrasion free method for braking of vehicles including trains.

It makes use of opposing tendency of eddy currents.

THE END