23-07-2014, 02:36 PM
MAGLEV TRAIN
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What is Maglev/Magnetic levitation?
The term "maglev" refers not only to the vehicles, but to the railway system
as well, specifically designed for magnetic levitation and propulsion.
Magnetic levitation, maglev, or magnetic suspension is a method by
which an object is suspended with no support other than magnetic fields.
Magnetic pressure is used to counteract the effects of the gravitational
and any other accelerations.
Using only ferromagnetic or paramagnetic materials it is impossible to
stably levitate against gravity; however, servomechanisms, the use of
diamagnetic materials, superconduction, or systems involving eddy
currents allow to achieve that.
Maglev Trains
A Maglev Train is a train that travels with out touching the 'tracks'.
It floats above the surface with magnetic levitation. The first an only high speed commercial magnetic levitation train in operation right now is the Shanghai Maglev Train in China. It is very cool, but it costs so much to build and run it is not really viable technology right now.
Technology
There are two particularly notable types of maglev technology:
Electrodynamic suspension (EDS) uses superconducting electromagnets
or strong permanent magnets which create a magnetic field that
induces currents in nearby metallic conductors when there is relative
movement which pushes and pulls the train towards the designed
levitation position on the guide way.
For electromagnetic suspension (EMS), electronically controlled
electromagnets in the train attract it to a magnetically conductive
(usually steel) track.
Electrodynamic Suspension
Electrodynamic suspension (EDS) is a form of magnetic levitation in
which there are superconductors which are exposed to time-varying
Magnetic fields. This induces eddy currents in the conductors that creates
a repulsive magnetic field which holds the two objects apart. EDS is used
for maglev trains, such as the Japanese SC Maglev.
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.
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.
Electromagnetic Suspension
Electromagnetic Suspension (EMS) is the magnetic levitation of an object achieved by constantly altering the strength of a magnetic field produced by Electromagnets using a feedback loop. In most cases the levitation effect is mostly due to permanent magnets as they don't have any power dissipation, with electromagnets only used to stabilize the effect.
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