Maglev train

THE MAGLEV TRAIN

1. Introduction

The MAGLEV train stands for magnetic levitation train and is a system of transportation
that suspends guides and propels vehicles, predominantly trains, using magnetic levitation
from a very large number of magnets for lift and propulsion. This method has the potential to
be faster, quieter and smoother than wheeled mass transit systems. The power needed for
levitation is usually not a particularly large percentage of the overall consumption; most of the
power used is needed to overcome air drag, as with any other high speed train.
The highest recorded speed of a Maglev train is 581 kilometers per hour (361 mph),
achieved in Japan in 2003, 6 kilometers per hour (3.7 mph) faster than the conventional TGV
wheel-rail speed record.
The first commercial maglev people mover was simply called "MAGLEV" and
officially opened in 1984 near Birmingham, England. It operated on an elevated 600-metre
(2,000 ft) section of monorail track between Birmingham International Airport and
Birmingham International railway station, running at speeds up to 42 km/h (26 mph); the
system was eventually closed in 1995 due to reliability problems.[2]
Perhaps the most well known implementation of high-speed maglev technology currently
operating commercially is the Shanghai Maglev Train, an IOS (initial operating segment)
demonstration line of the German-built Transrapid train in Shanghai, China that transports
people 30 km (19 mi) to the airport in just 7 minutes 20 seconds, achieving a top speed of
431 km/h (268 mph), averaging 250 km/h (160 mph).

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2. Technology

2.1. 0verview

The term "maglev" refers not only to the vehicles, but to the railway system as well,
specifically designed for magnetic levitation and propulsion. All operational
implementations of maglev technology have had minimal overlap with wheeled train
technology and have not been compatible with conventional rail tracks. Because they cannot
share existing infrastructure, these maglev systems must be designed as complete
transportation systems.
There are two particularly notable types of maglev technology:
 For electromagnetic suspension (EMS), electromagnets in the train attract it to a
magnetically conductive (usually steel) track.
 Electrodynamic suspension (EDS) uses electromagnets on both track and train to
push the train away from the rail.
Another experimental technology, which was designed, proven mathematically, peer
reviewed, and patented, but is yet to be built, is the magnetodynamic suspension (MDS),
which uses the attractive magnetic force of a permanent magnet array near a steel track to lift the
train and hold it in place. Other technologies such as repulsive permanent magnets and
superconducting magnets have seen some research.

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2.2. Electromagnetic suspension

In current electromagnetic suspension (EMS) systems, the train levitates above a steel rail
while electromagnets, attached to the train, are oriented toward the rail from below. The
system is typically arranged on a series of C-shaped arms, with the upper portion of the arm
attached to the vehicle, and the lower inside edge containing the magnets. The rail is situated
between the upper and lower edges.
Magnetic attraction varies inversely with the cube of distance, so minor changes in distance
between the magnets and the rail produce greatly varying forces. These changes in force are
dynamically unstable - if there is a slight divergence from the optimum position, the
tendency will be to exacerbate this, and complex systems of feedback control are required to
maintain a train at a constant distance from the track, (approximately 15 millimeters (0.6 in)).
[20][21]
The major advantage to suspended maglev systems is that they work at all speeds, unlike
electrodynamic systems which only work at a minimum speed of about 30 km/h. This
eliminates the need for a separate low-speed suspension system, and can simplify the track
layout as a result. On the downside, the dynamic instability of the system demands high
tolerances of the track, which can offset, or eliminate this advantage. Laithwaite, highly
skeptical of the concept, was concerned that in order to make a track with the required
tolerances, the gap between the magnets and rail would have to be increased to the point
where the magnets would be unreasonably large.[19] In practice, this problem was addressed
through increased performance of the feedback systems, which allow the system to run with
close tolerances.

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2.3. Electrodynamic suspension

In electrodynamic suspension (EDS), both the rail and the train exert a magnetic field,
and the train is levitated by the repulsive force between these magnetic fields. The magnetic
field in the train is produced by either superconducting magnets (as in JR-Maglev) or by an
array of permanent magnets (as in Inductrack). The repulsive force in the track is created by
an induced magnetic field in wires or other conducting strips in the track. A major
advantage of the repulsive maglev systems is that they are naturally stable—minor
narrowing in distance between the track and the magnets creates strong forces to repel the
magnets back to their original position, while a slight increase in distance greatly reduces
the force and again returns the vehicle to the right separation.

Repulsive systems have a major downside as well. At slow speeds, the current induced in
these coils and the resultant 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 gear to 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-speed operation. Another downside is that the repulsive system naturally
creates a field in the track in front and to the rear of the lift magnets, which act against the
magnets and create a form of drag. This is generally only a concern at low speeds, at higher
speeds the effect does not have time to build to its full potential and other forms of drag
dominate.[19]
The drag force can be used to the electrodynamic system's advantage, however, as it
creates a varying force in the rails that can be used as a reactionary system to drive the
train, without the need for a separate reaction plate, as in most linear motor systems.
Laithwaite led

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development of such "traverse-flux" systems at his Imperial College laboratory. Alternately,

propulsion coils on the guideway are used to exert a force on the magnets in the train and
make the train move forward. The propulsion coils that exert a force on the train are
effectively a linear motor: an alternating current flowing through the coils generates a
continuously varying magnetic field that moves forward along the track. The frequency of
the alternating current is synchronized to match the speed of the train. The offset between the
field exerted by magnets on the train and the applied field creates a force moving the train
forward.

2.4. Pros and cons of different maglev technologies

The pros of the electromagnetic suspension (EMS) are:

 The magnetic fields exerted by this type of technology are weaker than other
type of technology;
 Trains using this type of suspension have no need of wheels or secondary
propulsion systems.

The cons of the electromagnetic suspension (EMS) are:

 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.

The pros of the electrodynamic suspension (EDS) are:

 Onboard magnets and large margin between rail and train enable highest recorded
train speeds (581 km/h) and heavy load capacity;
 This type of suspension can be cooled with inexpensive liquid nitrogen.

The cons of the electrodynamic suspension (EDS) are:

 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;
 Vehicles using this type of suspension must be wheeled for travel at low speeds.

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The pros of the Inductrack System (MDS) are:

 Failsafe Suspension—no power required to activate magnets;
 The magnetic field is localized below the car;
 This system can generate enough force at low speeds (around 5 km/h) to levitate maglev
train;
 In case of power failure, the cars slow down on their own safely.

The cons of the Inductrack System (MDS) are:

 The system requires either wheels or track segments that move for when the vehicle
is stopped;
 The technology is new and still under development (as of 2008) and as yet
has no commercial version or full scale system prototype.

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2.5. Comparison between two different maglev technologies

The graph below illustrates a comparison between EDS and EMS technologies, in terms
of acceleration. We can see that the Shanghai Maglev Train, which uses EDS technology
reaches its top speed at about 211 seconds after leaving the station, while the German
Transrapid, using EMS technology, attains its maximum speed in about 310 seconds, but the
Transrapid’s top speed is considerably lower than the Shanghai Maglev’s top speed.

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3. Power and energy usage

The energy used for maglev trains is electrical energy, and therefore maglev trains are more
environmentally friendly than other transportation systems nowadays. The electrical energy is
converted into electromagnetic energy.
Most of the energy is used to accelerate the train, and may be regained when the train slows
down. This technology is called regenerative braking. The energy is also used to make the train
levitate and to stabilize the movement of the train. The main part of the energy is needed to
force the train through the air, therefore to overcome air drag. A big advantage of the magnetic
levitation systems is the lack of friction between the tracks and wheels. Also some energy is
used for air conditioning, heating, lighting and other miscellaneous systems.

At very low speeds the percentage of power (energy per time) used for levitation can be
significant. Also for very short distances the energy used for acceleration might be
considerable. But the power used to overcome air drag increases with the cube of the
velocity, and hence dominates at high speed (note: the energy needed per mile increases by
the square of the velocity and the time decreases linearly.).

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ADVANTAGES

1) The foremost advantage of maglev trains is the fact that it doesn't have moving parts as
conventional trains do, and therefore, the wear and tear of parts is minimal, and that reduces
the maintenance cost by a significant extent.

2) More importantly, there is no physical contact between the train and track, so there is no
rolling resistance. While electromagnetic drag and air friction do exist, that doesn't hinder
their ability to clock a speed in excess of 200 mph.

3) Absence of wheels also comes as a boon, as you don't have to deal with deafening noise that
is likely to come with them.

4) Maglevs also boast of being environment friendly, as they don't resort to internal
combustion engines.

5)These trains are weather proof, which means rain, snow, or severe cold don't really
hamper their performance.

6)Maglev systems are energy efficient. For long distance travel they use about half the energy
per passenger as a typical commercial aircraft.

7) Experts are of the opinion that these trains are a lot safe than their conventional counterparts
as they are equipped with state-of-the-art safety systems, which can keep things in control even
when the train is cruising at a high speed.

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DISADVANTAGES

1) Cost

While the advantages of Maglev Train System may seem quite promising in themselves, they are
not enough to overshadow the biggest problem with the maglev trains: the high cost incurred on
the initial setup. While the fast conventional trains that have been introduced of late, work fine on
tracks which were meant for slow trains, maglev trains require an all new set up right from the
scratch. As the present railway infrastructure is of no use for maglevs, it will either have to be
replaced with the Maglev System or an entirely new set up will have to be created―both of
which will cost a decent amount in terms of initial investment. Even though inexpensive as
compared to EDS, it is still expensive compared to other modes.

2) Impact

Although the tracks could be elevated, there would still be the addition of guideways crossing
great amounts of land.

3) Energy Consumption

Larger train cars are tougher to levitate and require quite a bit more energy, making them less
efficient.
4) Safety
While the MagLev can be safer overall, any infrequent accidents that do occur are likely to be
more catastrophic due to the elevated guideways and incredible speeds..

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CONCLUSION

The potential of maglev trains represents a transformative advancement in transportation

technology, offering faster, more efficient, and environmentally friendly alternatives to conventional
rail and road systems. By employing magnetic levitation to eliminate friction, these trains achieve
higher speeds and smoother rides, reducing travel times significantly. Moreover, maglev technology,
with its reduced number of moving parts, promises lower maintenance costs and greater reliability.
Despite the high initial investment and infrastructure requirements, the long-term benefits in terms
of reduced urban congestion, lower carbon emissions, and enhanced connectivity make maglev
trains a compelling option for modernizing national transportation infrastructures and advancing
towards sustainable mobility solutions.

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Reference

www.google.com
www.wikipedia.org
www.studymafia.org

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