Maglev

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Maglev Magnetic Leviation

• Driving without wheels, Flying without wings
• Under the Esteemed Guidance of

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Magnetic Leviation

• 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.

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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

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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

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Electromagnetic Suspension(EMS)

• Electromagnetic Suspension uses electromagnets to
  leviate the train

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Principle of Magnetic Leviation

• In the EMS-attractive system, the 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.

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• The rail, which is in the shape of an inverted T,
  is a ferromagnetic rail.
• When a current is passed 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.

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Principle of Propulsion

• 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

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• 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

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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

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Principle of Lateral Guidance

• 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.

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Electrodynamic Suspension

• Electrodynamic Suspension uses Superconductors
  for leviation,propulsion and lateral guidance

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Superconductivity

• Superconductivity occurs in certain materials at
  very low temperatures.
• When superconductive, a material has an
  electrical resistance of exactly zero.
• It is also characterized by a phenomenon called
  the Miessner effect. This is the ejection of any
  sufficiently weak magnetic field from the
  interior of the superconductor as it transitions
  into the superconducting state.

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Principle of Magnet Levitation

• The passing 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.

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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.

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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.

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The SCM (Super Conducting Magnet)

• Each SCM 4 SC coils. The SCM features high
  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.

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Pros and Cons of Different Technologies
Technology Pros Cons
EMS (Electromagnetic suspension) 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 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.

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Technology Pros Cons
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 Strong magnetic fields onboard the train would make the train inaccessible to passengers 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.

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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).
• 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 non-combustible, poor penetration
  transmitters of heat, and able to withstand fire.

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Current Projects

• Currently operational systems include Transrapid
  (Germany ) 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
• Germany and Japan have been the pioneering
  countries in MagLev research

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Other Applications

• 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!

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Conclusion

• 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-contact 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

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