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TRANSCRIPT
Terry Brown
WRIT 340
12/2/11
Maglevs: Where Flying Trains come from and Where They’re Headed
Introduction
“Where is my flying car?” has become an idiomatic expression often used to decry one’s
frustration with the lack of advancement of modern technology. With more and more
technologies that only existed in the realm of science fiction crossing into reality, it seems
puzzling that one of its main staples, the flying car, has not made the leap yet. Mankind is
making progress, however; while there may be no flying car in the original sense of the term yet,
flying, or rather floating trains are already in existence. Magnetic levitation (maglev for short) is
a technology that has been in the works for some time, and has already been implemented in a
few cases around the world. Combining some of the benefits of airplanes and trains, they offer
the high capacity and easy accessibility of trains with the reduced friction of a flying body using
the power of electro-magnets. Although it does have some setbacks and challenges to overcome
before widespread adoption, the technology has proven itself a worthy successor to high speed
rail through projects of both small and large scales.
Maglev
Though one might assume that the maglev is a brand new technology because they have
only become widely adopted in recent years, its origins actually date back to the mid-19th
century. The first mention of related technologies appears in a rough description of the maglev
concept given by Charles Wheatstone of King’s College in the 1840’s [1]. The first related patent
was issued in the US under the title “electric traction apparatus” to Alfred Zehden in 1905 [2]
Zehden’s patent describes the basis of what is now known as a linear induction motor: a
propulsion device that produces motion by using magnets to create a tractive force between a
track and a body instead of using a rotating shaft to produce torque, as is the case in conventional
motors. This is one of the core technologies used for maglev, as it allows a contactless method of
propulsion for a car on a track. This patent came amid a heightened interest in electricity
resulting from the widespread adoption of the light bulb and electric motor around this time; it
was, however, most likely treated as a mere novelty due to its lack of a practical application. It
wasn’t until Eric Laithwaite, an undergraduate at Manchester University, took interest in the
subject in the 1948 that a full scale model was built [3].
The basic physics of a linear motor is easy to
demonstrate: using two magnets, put them close
together on a smooth surface and turn them so that they
repel each other; hold one of the magnets so that it can’t
move and the other will slide away [4]. Repeat this
simple process and the effect can be used to propel a
body forward. The basic layout of a linear motor is
shown in fig (1); a body containing magnets is placed
upon a “track” of electromagnets with alternating polarity. Assume that the body is in state A
when the electromagnet is turned on. The current in the electromagnet is then reversed, reversing
the polarity of the electromagnet. This causes the magnets in the track to repel the magnets in the
body, propelling it forward, as shown in state B. The magnet then realigns itself, returning to
state A a bit down the track from its beginning state. The cycle is then repeated, with the current
and polarity of the electromagnet reversed so that the body is propelled further forward. Another
Fig. (1). A representation of the linear motor. The grey squares represent electromagnets in the track, and those above them are the magnets in the body. (Sifr/Wikimedia Commons)
example of this is in fig. (2), with tracks on both sides of the vehicle, instead of directly
underneath it. When the alternation of the current is conducted at the right frequency, the body is
continuously propelled forward. The result is a system that can move a body forward without the
need for any physical contact. This is called a linear induction motor, because the system works
as if a regular motor was “unrolled” onto a linear track, with the rotor placed in the body and the
stators, or stationary magnets, unraveled onto the track.
Magnetic Levitation: EDS and EMS
Laithwaite, now known as the father of
maglev, continued his research on the linear
induction motor after becoming a professor at
Imperial College of London in 1964 [3]. He worked
to increase their efficiency and strength, and thus their
practicality in real world applications. The next big
step in the field of maglev came with Laithwaite’s
development of the magnetic river in 1974: an
electrodynamic suspension (EDS) magnetic levitation
system, or in other words, a magnetic system that works to keep a body afloat above a track [5].
One interpretation of this is to have another set of electromagnets in the track as shown in
fig. (3). In this configuration, the electromagnets in the tracks serve two purposes. The first is to
act as a linear motor, similar to the function of the track shown in fig. (2). The second is to repel
the train from the ground and walls, ensuring that it is stably suspended above the tracks [6].
This is achieved by taking advantage of Lenz’s and Faraday’s laws: a changing magnetic field,
as occurs when the magnets in the body are passing by, generates an electromotive force in the
Fig. (2). A top view of an EDS track. In this case, there is dual track propelling a train from two sides. (Stannerd/Wikimedia Commons)
Fig. (3). A front view of an EDS track. Inductive forces cause the track to repel the magnets in train, causing levitation. (Yosemite/Wikimedia Commons)
electromagnetic circuit in the tracks. While the mathematical proof for this system is beyond the
scope of this article, simply put this means that if the train passes by the electromagnets in the
track quickly enough, the resulting change in magnetic field will induce a current within the
electromagnets. This in turn causes the track to produce a repelling magnetic force, represented
by the arrows in fig. (3), which are used both to levitate the train and to keep it within the width
of the track. When implemented successfully, this system makes the train “fly,” lifting it up to a
few inches above the ground [5]. The advantages of EDS are that the levitation system itself does
not require power, and can be integrated with the Linear motor. EDS does, however require the
train to have wheels in order to accelerate to the “take off” speed required for the levitation force
to become strong enough to lift the train. EDS also means that a strong magnetic field is created
on-board, which can pose a threat to pace-makers and
other artificial organs. There is currently no work-
around for this, so trains relying on this system remain
inaccessible to those with artificial hearts. An advanced
form of this EDS is used in the Japanese Shinkansen
Maglev (fig. 4) currently under construction, but as of
yet it remains unused in any commercial system.
Meanwhile, an alternative technology to EDS
was developed for Maglevs that didn’t require such strong magnetic fields. Called
electromagnetic suspension (EMS), it is based on the simple idea of using active magnets in the
track to support the train, as opposed to EDS where inactive magnets are induced into creating a
repelling force. EMS systems commonly use permanent magnets, which don’t require power, to
levitate the body. The problem with this is that placing a repelling magnet atop another magnet
Fig. (4). The Japanese JR-Maglev. An example of an EDS Maglev. (Yosemite/Wikimedia Commons)
does not cause the top magnet to simply float above the bottom magnet; the system is unstable,
meaning the top magnet will be pushed to the side, in this case causing the train to derail. To
address this problem, modern EMS systems supplement the permanent magnets with computer-
operated electro-magnets to keep the train in place. This system has the advantage of being able
to levitate the body at lower speeds, and with smaller magnetic fields than EDS; however they
require closer monitoring and constant adjustments
of the electromagnets to maintain stability [7].
This system has been used in all commercial
Maglev systems so far, including the German
Transrapid system built by Siemens and
ThyssenKrupp, recently used for the Shanghai Maglev Train shown in fig. (5) [7].
Maglev: a Promising Technology
Together, the linear propulsion motor and
magnetic levitation system provide a frictionless alternative to the traditional train. Thanks to
linear induction, there are no moving parts in the propulsion system, and the magnetic
suspension means that maglev trains do not touch the ground. This means that the only drag
experienced is aerodynamic and electromagnetic, allowing Maglevs to reach top speeds of over
360 mph with a lower energy consumption than their wheeled predecessors. A beneficial side
effect of this is that the trains are quiet and stable, since the only noise and disturbances they
generate come from the displacement of air.
The lack of moving parts also means that these trains need less maintenance. Since they
are not in contact with the rails, there in no wear on the trains or rails. Maintenance is minimal,
and the vehicles follow a maintenance schedule closer to that of aircraft than that of traditional
Fig. (5). The German-built Shanghai Maglev in China. An example of an EMS Maglev. (Gugganij/Wikimedia Commons)
trains, meaning that their maintenance schedules are based on hours of operation rather than
distance travelled [8]. Maglevs are also immune to weather since their tracks are not subject to
heat deformation or freezing, reducing traditional constraints placed on rail travel. This makes
the technology ideal for any location with extreme weather.
Lastly and most importantly, linear motors allow maglevs to accellerate and deccelerate
to and from high speeds in a short distance. This makes them ideal both for rapid inner-city
travel since this means that they can accellerate to their top speeds even when stations are close
together. Though they are not quite as fast as the average jet plane, with top speeds of 360mph as
opposed to airliner’s cruising speeds of around 500mph, maglevs can also be a competitive
alternative along mid-range routes because train travel does not require the security and
preperation necessary to travel through an airport, reducing travel time. For routes of up to 500
miles, taking a maglev could easily become cheaper, quicker, and safer than travelling by air.
The Limitations
Despite all of these advantages of Maglevs over conventional rail, there are still many
challenges that they must overcome in order to win the battle for prominence on the rails. The
first is perception of safety. In the decades of testing that maglevs have gone through so far, they
have encountered only a handful of accidents, which is not a bad track record. Many in the
public remain wary of the technology, however, since it has had limited use in commercial
operation and has yet to prove itself free of negative health effects or other threats to the public’s
wellbeing. Just recently, a project intended to extend the Shanghai Maglev was shelved, partly
due to concerns by the track’s neighbors over potential health problems arising from the
magnetic fields [9]. Since the Shanghai Maglev uses EMS, which has weaker magnetic fields
than the EDS, this is likely to be an even greater issue for EDS based technologies.
The maglev’s other weakness, and the main reason why the Shanghai Maglev extension
failed, is cost. Building a track of around 50 miles can cost billions of dollars, several times more
than any conventional rail technology. While in a few areas, particularly those with high
ridership, Maglevs do make sense, for the majority of cases they remain impractical. To date, the
only maglev systems built have been used either as experimental tracks, for airport
transportation, or for exhibition purposes.
Future
As of today (Dec. 2011), there are two commercial Maglev projects that have overcome
these hurdles and are currently in the works. The first is an inner-city track of about 6 miles to be
built in Beijing, called the Beijing S1 line. This would become the fourth Maglev service open to
the public in addition to those already in operation in China, Korea, and Japan. This is a
relatively modest project with expected high speeds of 65mph and a slated completion date of
2013 [10]. It is likely that most Maglev projects in the near future will be along similar scales.
A much more ambitious project is also underway in Japan; this is the Chuo Shinkansen,
or “central bullet train.” The Chuo Shinkansen is an ambitious project attempting to connect the
two largest Japanese cities, Tokyo and Osaka, with an EDS Maglev train. The project has already
won government approval, and construction is expected to begin in 2014. The first portion of the
track is expected to open around 2027, with the full length expected to open around 2045. This
long timescale results both from the cost, expected to be over $55billion, as well as the fact that a
majority of the track will be built underground [11]. This would make the roughly 350 mile
journey between the cities possible in as little as one hour, and would be the first large scale
inter-city Maglev to be built.
There are numerous other proposals for both short and long distance Maglevs around the
world, but few seem likely to begin construction in the near future primarlity due to economic
concerns. It appears that the long-term success of Maglevs will depend on the success of the
pioneering projects being implemented now, as well as the ability of companies to lower the cost
of the technology.
Conclusion
Maglev is a technology that has been around for some time, but has only recently become
feasible after years of development. Even now, its practicality is questionable due to its high
costs. As shown in recent implementations and upcoming projects, however, Maglev shows great
potential and is continuously improving thanks to improving technologies. Soon, with any luck it
will become a much faster and more reliable alternative to conventional rail; and once mankind
is able to figure out the secret to flying trains, we can only assume that the flying cars cannot be
too far behind.
Bibliography
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Proquest, 2006.
[2] A. Zehden. “Electric Traction Apparatus.” US Patent 782,312. Feb 14, 1905.
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