Maglev Trains 66731d

Driving without wheels, Flying without wings

MAGLEV –MAGNETIC LEVIATION

MAGNETIC LEVIATION 

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Magnetic levitation is the use of magnetic fields to levitate a (usually) metallic object. Manipulating magnetic fields and controlling their forces can levitate an object. Using either Ferromagnetism or Diamagnetisim object can be leviated. A superconductor is perfectly diamagnetic and electromagnets can exhibit varying levels of ferromagnetism Most imoportant application of Magnetic Leviation is Transrapid magnetic lift trains.

BASIC PRINCIPLE OF MAGLEV TRAINS Maglev trains have to perform the following functions to operate in high speeds 1.Leviation 2.Propulsion 3.Lateral Guidance

TYPES OF MAGLEV TRAINS Based on the technique used for Leviation the are two types of Maglev trains

1. Electromagnetic Suspension -Attractive 2. Electrodynamic Suspension -repulsive

ELECTROMAGNETIC SUSPENSION(EMS) 

Electromagnetic Suspension uses electromagnets to leviate the train

PRINCIPLE OF MAGNETIC  In the EMS-attractive system, the LEVIATION electromagnets which do the work of levitation are attached on the top side of a casing that extends below and then curves back up to the rail that is in the center of the track.

The rail, which is in the shape of an inverted T, is a ferromagnetic rail.  When a current is ed through it, and the electromagnet switched on, there is attraction, and the levitation electromagnets, which are below the rail, raise up to meet the rail. The car levitates. 

PRINCIPLE OF PROPULSION 

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A linear electric motor (LEM) is a mechanism which converts electrical energy directly into linear motion without employing any intervening rotary components Linear Induction Motor (LIM) is basically a rotating squirrel cage induction motor opened out flat Instead of producing rotary torque from a cylindrical machine it produces linear force from a flat one. LIM thrusts vary from just a few to thousands of Newtons , depending mainly on the size and rating Speeds vary from zero to many meters per second and are determined by design and supply frequency

A conventional rotary synchronous motor , is made up of two rings of alternating north and south magnetic poles.  The outer ring (the stator) is stationary, while the inner one (the rotor) is free to rotate about a shaft.  The polarity of the magnets on one (either) of these rings is fixed; this element is known as the field.  The magnets of the other ring, the armature, change their polarity in response to an applied alternating current. 

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Attractive forces between unlike magnetic poles pull each element of the rotor toward the corresponding element of the stator. Just as the two poles are coming into alignment, the polarity of the armature magnets is reversed, resulting in a repulsive force that keeps the motor turning in the same direction. The armature poles are then reversed again, and the motor turns at a constant speed in synchronism with the alternating current which causes the change in polarity

GAP SENSOR This attractive force is controlled by a gap sensor that measures the distance between the rails and electromagnets  This attractive force is controlled by a gap sensor that measures the distance between the rails and electromagnets 

PRINCIPLE OF LATERAL GUIDANCE 

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The levitation magnets and rail are both U shaped(with rail being an inverted U). The mouths of U face one another.

This configuration ensures that when ever a levitational force is exerted, a lateral guidance force occurs as well. If the electromagnet starts to shift laterally from the center of the rail, the lateral guidance force is exerted in proportion to the extent of the shift, bringing the electromagnet back into alignment.

ELECTRODYNAMIC SUSPENSION 

Electrodynamic Suspension uses Superconductors for leviation,propulsion and lateral guidance

PRINCIPLE OF MAGNET LEVITATION

•The ing of the superconducting magnets by figure eight levitation coils on the side of the tract induces a current in the coils and creates a magnetic field. This pushes the train upward so that it can levitate 10 cm above the track. •The train does not levitate until it reaches 50 mph, so it is equipped with retractable wheels.

PRINCIPLE OF PROPULSION •The propulsion coils located on the sidewalls on both sides of the guideway are energized by a three-phase alternating current from a substation, creating a shifting magnetic field on the guideway. •The on-board superconducting magnets are attracted and pushed by the shifting field, propelling the Maglev vehicle. •Braking is accomplished by sending an alternating current in the reverse direction so that it is slowed by attractive and repulsive forces.

PRINCIPLE OF LATERAL GUIDANCE •When one side of the train nears the side of the guideway, the super conducting magnet on the train induces a repulsive force from the levitation coils on the side closer to the train and an attractive force from the coils on the farther side. •This keeps the train in the center.

THE SCM (SUPER CONDUCTING  Each SCM 4 SC coils. The SCM features high MAGNET) reliability and high durability.  The cylindrical unit at the top is a tank holding liquefied helium and nitrogen.  The bottom unit is an SC coil alternately generating N poles and S poles.

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An EDS system can provide both leviation and propulsion using an onboard linear motor. EMS systems can only levitate the train using the magnets onboard, not propel it forward. Over long distances where the cost of propulsion coils could be prohibitive, a propeller or jet engine could be used.

PROS AND CONS OF DIFFERENT TECHNOLOGIES

TECHNOLOGY EMS (Electromagnetic suspension)

PROS

Magnetic fields inside and outside the vehicle are less than EDS; proven, commercially available technology that can attain very high speeds (500 km/h); no wheels or secondary propulsion system needed

CONS

The separation between the vehicle and the guideway must be constantly monitored and corrected by computer systems to avoid collision due to the unstable nature of electromagnetic attraction; due to the system's inherent instability and the required constant corrections by outside systems, vibration issues may occur.

TECHNOLOGY

PROS

EDS (Electrodynamic suspension)

Onboard magnets and large margin between rail and train enable highest recorded train speeds (581 km/h) and heavy load capacity; has recently demonstrated (December 2005) successful operations using high temperature superconductors in its onboard magnets, cooled with inexpensive liquid nitrogen

CONS Strong magnetic fields onboard the train would make the train inaccessible to engers with pacemakers or magnetic data storage media such as hard drives and credit cards, necessitating the use of magnetic shielding; limitations on guideway inductivity limit the maximum speed of the vehicle; vehicle must be wheeled for travel at low speeds.

ADVANTAGES OF MAGNETIC LEVITATED TRANSPORTATION SYSTEM  Maglev uses 30% less energy than a high-speed train traveling at the same speed (1/3 more power for the same amount of energy).

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The operating costs of a maglev system are approximately half that of conventional long-distance railroads. Research has shown that the maglev is about 20 times safer than airplanes, 250 times safer than conventional railroads, and 700 times safer than automobile travel. Maglev vehicle carries no fuel to increase fire hazard The materials used to construct maglev vehicles are noncombustible, poor penetration transmitters of heat, and able to withstand fire.

CURRENT PROJECTS 

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Currently operational systems include Transrapid ( ) and High Speed Surface Transport (Japan ). There are several other projects under scrutiny such as the SwissMetro, Seraphim and Inductrack. All have to do with personal rapid transit and Japan have been the pioneering countries in MagLev research

OTHER APPLICATIONS 

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NASA plans to use magnetic levitation for launching of space vehicles into low earth orbit. Boeing is pursuing research in MagLev to provide a Hypersonic Ground Test Facility for the Air Force. The mining industry will also benefit from MagLev. There are probably many more undiscovered applications!

CONCLUSION

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The MagLev Train: Research on this ‘dream train' has been going on for the last 30 odd years in various parts of the world. The chief advantages of this type of train are: Non- and non-wearing propulsion, independent of friction, no mechanical components like wheel, axle. Maintenance costs decrease The MagLev offers a cheap, efficient alternative to the current rail system. A country like India could benefit very much if this were implemented here. Further possible applications need to be explored