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
Eddy currents are electric currents inducedin conductors when exposed to a changing magnetic field;due to relative motion of the field source and conductor ordue 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 andthus induce magnetic fields.
Š Eddy current brakes, like conventional friction brakes, are responsible for slowing an object, such as rotating machinery, amoving train, or even a roller coaster.These brakes make use of opposing tendency of eddy currents.The drawbacks of ordinary brakes which uses mechanicalblocking could be eliminated by use of a more simple andeffective mechanism known as eddy current brakes.Š There are two basic types: (1)circular (2)linear
COMPONENTS AND CONSTRUCTIONAL FEATURES OF 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, theyre being no contact between the two for the purpose of torque transmission. Consequently there is no wear as in friction brake.
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 andfixed 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 anelectromagnet, generating eddy currents in the disc. The magneticinteraction between the applied field and the eddy currents slow downthe rotating disc. Thus the wheels of the vehicle also slow down sincethe wheels are directly coupled to the disc of the eddy current brake,thus producing smooth stopping motion.
HOW DOES AN EDDY CURRENT BRAKE STOP SOMETHING MOVING? Suppose we have a huge solid block of copper mounted onwheels. 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 trainhad to pass nearby.As the copper approached the magnet eddy currents would begenerated inside the copper which would their own magneticfield.
As the front part approached the magnet eddy currents in that bitof copper would try to generate a repulsive magnetic field to slowdown copper’s approach to magnet. As the front passed by, slowing down, the currents there wouldreverse, generating an attractive magnetic field that tried to pull thetrain back again. (again, slowing it down). The copper would heat up the eddy currents swirled insideit, gaining the kinetic energy lost by the train as it slowed down.
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 needregular inspection and routinely wear out. Its been estimated that switchingan electric train from friction brakes to eddy-current brakes could halve thecost 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 rollercoasters.There are a number of major commercial applications of eddycurrent brake technology in the mining, railroad, and elevatorindustries. Well also find eddy current brakes in all kinds of machines, suchas circular saws and other power equipment. And theyre used inthings like rowing machines and gym machines to apply extraresistance 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.