MAGNET A magnet is any object that has a magnetic field. It attractsferrous objects like pieces of iron, steel, nickel and cobalt. These day’smagnets are made artificially in various shapes and sizes depending on theiruse. One of the most common magnets the bar magnet is a long, rectangular barof uniform cross-section that attracts pieces of ferrous objects. The magneticcompass needle is also commonly used. The compass needle is a tiny magnet whichis free to move horizontally on a pivot.
One end of the compass needle pointsin the North direction and the other end points in the South direction. The endof a freely pivoted magnet will always point in the North-South direction. Theend that points in the North is called the North Pole of the magnet and the endthat points south is called the South Pole of the magnet. It has been proven byexperiments that like magnetic poles repel each other whereas unlike polesattract each other. MAGNETICFIELD AND FIELD LINES Magnetic Field The space surroundinga magnet, in which magnetic force is exerted, is called a magnetic field. If a barmagnet is placed in such a field, it will experience magnetic forces. Magnetic Lines of ForceWhen a small northmagnetic pole is placed in the magnetic field created by a magnet, it willexperience a force. The magnetic lines of force are the lines drawn in amagnetic field along which a north magnetic pole would move.
The direction of amagnetic line of force at any point gives the direction of the magnetic forceon a north pole placed at that point. Since the direction of magnetic line offorce is the direction of force on a North Pole, so the magnetic lines of forcealways begin on the N-pole of a magnet and end on the S-pole of the magnet. Asmall magnetic compass when moved along a line of force always sets itselfalong the line tangential to it. So, a line drawn from the South Pole of thecompass to its North Pole indicates the direction of the magnetic field. MAGLEV TECHNOLOGY Thistechnology uses monorail track with linear motors, these trains move on specialtracks rather than the mainstream conventional train tracks. They use verypowerful electromagnets to reach higher velocities, they float about 1- 10 cmsabove the guide way on a magnetic field .These trains are propelled by theguide ways. Once the train is pulled into the next section the magnetismswitches so that the train is pulled on again.
The electro magnets run thelength of the guide way. THE MECHANICS OF MAGLEV TRAINMagnetic levitation trains operate through the use of electromagnets, which are magnets created by electric current. An electromagnet isdefined as “a coil of insulated wire wound around an iron or steel cylinder”,and functions when current flows through the coil a magnetic field is produced.These electromagnets are used to lift the train above its track, as well aspropel it forward. There are three main types of Maglev trains: i) ELECTROMAGNETICSUSPENSION It isthe magnetic levitation of an object achieved by constantly alteringthe strength of a magnetic field produced by electromagnets usinga feedback loop. In most cases the levitation effect is mostly due topermanent magnets as they don’t have any power dissipation, with electromagnetsonly used to stabilize the effect. In these kinds of fields an unstableequilibrium condition exists. Although static fields cannot give stability, EMSworks by continually altering the current sent to electromagnets to change thestrength of the magnetic field and allows a stable levitation to occur.
In EMSa feedback loop which continuously adjusts one or more electromagnetsto correct the object’s motion is used to cancel the instability. In this system Electromagnets are attached to thetrain and also attached to the guide way track. They have ferromagnetic statorson the track and they help them to levitate the train.
They have guidancemagnets on the sides of the track they are laid complete along the track Acomputer is used to control the height of levitation of train they make uslevitate about ( 1 – 15 cms ).The Max speed these trains could reach is about438km/hr. They have on-board battery power supply which gives surplus amount ofenergy required to run a cabin. ii) ELECTRODYNAMIC SUSPENSION Superconducting magnets are placed under the train. By this systemthe train could levitate about 10 cm from the guide way.
The magnetic fieldwhich helps the train to levitate is due to use of superconducting magnets. The force in the track is created byinduced magnetic field in wires or conducting strips in the track. In electrodynamic suspension (EDS), both the guide way and thetrain exert a magnetic field, and the train is levitated by the repulsive andattractive force between these magnetic fields. EDS systems have a majordownside as well. At slow speeds, the current induced in these coils and theresultant magnetic flux is not large enough to support the weight of the train.
For this reason, the train must have wheels or some other form of landing gearto support the train until it reaches a speed that can sustain levitation.Since a train may stop at any location, due to equipment problems for instance,the entire track must be able to support both low-speed and high-speedoperation. Another downside is that the EDS system naturally creates a field inthe track in front and to the rear of the lift magnets, which acts against themagnets and creates a form of drag. .
iii) INDUCTRACK SYSTEM It is a suspension fail system, no power is required to activatemagnets. Magnetic field is located below the car, they can generate enoughforce at low speeds (around 5 km/h) to levitate maglev train. In case of powerfailure cars slow down on their own safely, permanent magnets are arranged inan array which helps in propulsion of the trains. They require either wheels ortrack segments that move for when the vehicle is stopped. Neither Inductracknor the Superconducting EDS are able to levitate vehicles at a standstill,although Inductrack provides levitation down to a much lower speed, wheels arerequired for these systems. EMS systems are wheel-less. THE MAGLEV TRACK Themagnetized coil running along the track, called a guideway, repels the largemagnets on the train’s undercarriage, allowing the train to levitate between0.
39 and 3.93 inches (1 to 10 cm) above the guideway. Once the train islevitated, power is supplied to the coils within the guideway walls to create aunique system of magnetic fields that pull and push the train along theguideway. The electric current supplied to the coils in the guideway walls isconstantly alternating to change the polarity of the magnetized coils. Thischange in polarity causes the magnetic field in front of the train to pull thevehicle forward, while the magnetic field behind the train adds more forwardthrust. Maglev trains float on a cushion of air, eliminating friction. Thislack of friction and the trains’ aerodynamic designs allow these trains toreach unprecedented ground transportation speeds of more than 500 kmph, ortwice as fast as Amtrak’s fastest commuter train. In comparison, a Boeing-777commercial airplane used for long range flights can reach a top speed of about905 kmph.
Developers say that maglev trains will eventually link cities thatare up to 1,609 km apart. At 500 kmph, you could travel from Paris to Rome injust over two hours. Application·NASA plans to use magnetic levitation for launching of space vehicles into lowearth orbit. ·Boeing is pursuing research in Maglev to provide a Hypersonic Ground TestFacility for the Air Force.·The mining industry will also benefit from Maglev. DEVELOPMENT OF MAGLEV TRAINS : There are different factors which are used in the development ofmaglev trains, these help in movement, stability, guidance etc of a train . PROPULSION:SomeEMS systems can provide both levitation and propulsion using an on board linearmotor.
But some EDS systems are like they can levitate the train using themagnets on board but cannot propel it forward. As such, vehicles need someother technology for propulsion. A linear motor (propulsion coils) mounted inthe track is one solution STABILITY:Anycombination of static magnets cannot be in a stable equilibrium.
Therefore adynamic magnetic field is required to achieve stabilization. EMS systems relyon active electronic stabilization which constantly measure the bearingdistance and adjust the electromagnet current accordingly. All EDS systems relyon changing magnetic fields creating electrical currents, and these can givepassive stability. Because maglev vehicles essentially fly, stabilisation ofpitch, roll and yaw is required by magnetic technology. In addition torotation, move forward and backward, sway (sideways motion) or heave (up anddown motions) can be problematic with some technologies. GUIDANCESomesystems use Null Current systems (also sometimes called Null Flux systems);they use a coil which is wound so that it enters two opposing, alternatingfields, so that the average flux in the loop is zero.
When the vehicle is inthe straight ahead position, no current flows, but if it moves off-line thiscreates a changing flux that generates a field that naturally pushes and pullsit back into line. This is the guidance system of maglev trains. EVACUATEDTUBESSomesystems (notably the Swissmetro system) propose the use of maglev traintechnology used in evacuated (airless) tubes, which is used to remove air drag.
This has the potential to increase speed and efficiency greatly, as most of theenergy for conventional maglev trains is lost due to aerodynamic drag. Onepotential risk for passengers of trains operating in evacuated tubes is that theycould be exposed to the risk of cabin depressurization unless tunnel safetymonitoring systems can repressurize the tube in the event of a trainmalfunction or accident.COMPARISON Comparison I Vehicle Design: Maglevis similar to other transport technology, but the implementation variesconsiderably according to the application. Choice of vehicle, weight, shape andlength dominate transport system design. There are 3 key issues that affect theEI of a transport system and are primarily determined by vehicle design.
Forhigh speed travel the dominant energy usage is to overcome aerodynamic drag.For constant speed travel EI is proportional to drag force per passenger.Airplanes do much better than it is possible for ground transportation becauseof lesser pressure at greater (12,000 m) height. Forlow-speed travel the dominant energy loss is due to the need to supply kineticenergy to change vehicle’s speed and this is lost when brakes are applied. Suspensionand propulsion losses are always significant. Not only is there a direct losssuch as wheel hysteresis and bearing friction but at high speed aerodynamicloss become more than direct losses.
With these facts in mind, consider thedesign aspect of the weight, shape and length. Weight:All transport technology has been moving in the direction of reducing vehicleweight, and using regenerative braking. Shape: Shapeis important because it affect aerodynamic loss and noise, both external andinternal. Even low speed vehicle should have modest streamlining and high speedvehicle need more extreme shapes. Japanese Fastech 360 train designed for360km/h, Trans rapid TR09 designed for 350-500 km/h.
the nose section is veryimportant for high speed, particularly for vehicles entering existing tunnels.For HSR the main aerodynamic drag is on the body, wheels and pantograph. Welldesigned maglev vehicle have less drag and are quieter than modern high speedtrains, even when going substantially faster. Length:Vehiclelength is a critical parameter. The frontal area is constrained by the assumedneed to provide height for standing head room and width for at least fourabreast sitting with reasonable comfort. With maglev the frontal can be lessthan for conventional trains because the suspension has less frontal area andthere is no pantograph. The minimum length is determined by passenger carryingability.
Comparison 2: Fuel Efficiency · Unlikethe previous forms of transportation, Maglev trains run on electricity ratherthan fossil fuels. Electricity is a renewable source of energy and can becreated in several different ways including nuclear, hydro and solar plants.Fossil fuels are non-renewable sources of energy.
They must be burnt, releasingcarbon emission in the atmosphere in order to produce energy ·Travellingat a speed of 300 mph and 150 mph. Maglev trains use 0.4 mega joules and 0.1mega joules per passenger mile respectively. An automobile travelling at aspeed of 60 mph with 20-mpg fuel efficiency uses 4 mega joules per passengerper mile. Using these numbers, Maglev trains moving at half this speed attainsefficiency 40 times greater than that of an automobile.
Comparison 3: Speed and cost: · Whencommuting in a car one’s average arrival time can be hard to calculate due totraffic and driving conditions. Everyone has been struck in traffic. Unannounced construction, gaperdelays, sometimes nothing at all can create massive delays on the roadway. · Caralso requires much maintenance. Automobiles must meet state standards in orderto be legal for the roads and all cars must be insured. This constantmaintenance and legal coverage becomes very costly for any common citizen.
· Planesas well experience delays. Prime weather and air traffic condition areessential in insuring passenger a safe flight. However, when these criteria arenot made, delays occur. · Inlife, just as in driving, there is no way to predict what will happen infuture. What we can do is to put the odds in our favour is to minimize risk.
That’s where maglev train come into play. Maglev trains have a dedicatedinfrastructure solely for the train itself. No other vehicles are compatiblewith their magnetic guide ways and so no other vehicles travel on it. Thismeans no traffic and no collisions.
Weather conditions have little to no effecton maglev trains except under severe conditions. So a train can travel evenwhen the weather is subpar. In an automobile or conventional locomotive wetconditions decreases friction between the vehicle and ground. This increasesstopping time and the probability that a vehicle may slip. The magnetic forcesat hand are unaffected by such condition. Since no contact is made between themaglev train and the railway. Less wear is put on each.
This means lessmaintenance. Less maintenance creates fewer delays while allowing lower ticketprices. ADVANTAGES Aircraft are theoretically flexible but commercial air routes arenot. High-speed maglevs are designed to compete on journey times with flightsof 800 kilometres (500 miles) or less. Additionally, while maglevs can serveseveral cities in between such routes and be on time in all weather conditions,airlines cannot come close to such reliability or performance.
Because maglevvehicles are powered by electricity and do not carry fuel, maglev fares areless susceptible to the heavy price swings created by oil markets. Travellingvia maglev also offers a significant safety margin over air travel sincemaglevs are designed not to crash into other maglevs or leave their guideways.Aircraft fuel is a significant danger during takeoff and landing as there arechances for accidents. In real-world situations the speed of maglev are lessthan aircraft, but maglev still save time due to less number of hurdles ittakes to travel in them as compared to air travel. With air travel, people needto spend time at airports for check-in, security, boarding, etc. In air travel,time is also consumed (primarily in busy airports) by the aircraft for taxing,waiting in queue for take-off and landing, which are negligible in case ofmaglev. Because no contact is made between the trains allow for nearfrictionless travel. This near frictionless travel has numerous benefitsincluding higher speeds, less noise, resistance to poor weather conditions, anddecreased maintenance.
Maglev trains initially cost more than conventionalmeans of transportation during construction, but with conventional transport,friction between tracks and wheels often causes damage over time, whichrequires both funds and labour to repair. Maglev trains do not experience thisphysical stress, and thus, require only slight further funding once they arebuilt. They are not entirely frictionless, however. They simply experience nosurface friction, which does help decrease maintenance and power consumption.Maglev trains do, however, still experience air resistance and slightelectromagnetic drag, but these conditions are present in negligible amounts.Maglev trains are quieter than conventional transport. Disadvantages:While the advantages of Maglev Train System may seem quite promising inthemselves, they are not enough to overshadow the biggest problem with themaglev trains: the high cost incurred on the initial setup. While the fastconventional trains that have been introduced of late, work fine on trackswhich were meant for slow trains, maglev trains require an all new set up rightfrom the scratch.
As the present railway infrastructure is of no use formaglevs, it will either have to be replaced with the Maglev System or anentirely new set up will have to be created?both of which will cost a decent amountin terms of initial investment. Even though inexpensive as compared to EDS, itis still expensive compared to other modes. Although Maglevs are pretty quiet, noise caused by air disturbance stilloccurs.. CONCLUSION These trains consume very less energy compared to conventionaltrains. They require no large engine kind of stuff as they run using linearmotors.
They Move a lot faster than normal trains because they are not affectedby ground friction, they would only have air resistance or drag resistance.They are incompatible with existing rail lines because they need a separatetrack to levitate, unlike the traditional high-speed trains. These technologyneeds to be implemented in large countries where transportation time can bereduced and it is also a safe and efficient way to travel. Initially the costis very high but it may decrease in near future. Nowthat we know how the technology work, we believe that maglev system can beresearch further to be used in advanced application and maglev technologies arein demand due to it beings environmentally friendly.