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How Maglev Trains Work
If you've been to an airport lately, you've probably noticed that air travel is
becoming more and more congested. Despite frequent delays, airplanes still
provide the fastest way to travel hundreds or thousands of miles. Passenger
air travel revolutionized the transportation industry in the last century,
letting people traverse great distances in a matter of hours instead of days
The first commercial maglev line made its debut in
December of 2003.
The only alternatives to airplanes -- feet, cars, buses, boats and conventional
trains -- are just too slow for today's fast-paced society. However, there is
a new form of transportation that could revolutionize transportation of the
21st century the way airplanes did in the 20th century.
A few countries are using powerful electromagnets to develop high-speed
trains, called maglev trains. Maglev is short for magnetic levitation, which
means that these trains will float over a guideway using the basic principles
of magnets to replace the old steel wheel and track trains. In this article,
you will learn how electromagnetic propulsion works, how three specific
types of maglev trains work and where you can ride one of these trains.
If you've ever played with magnets, you know that opposite poles attract
and like poles repel each other. This is the basic principle behind
electromagnetic propulsion. Electromagnets are similar to other magnets in
that they attract metal objects, but the magnetic pull is temporary. As you
can read about in How Electromagnets Work, you can easily create a small
electromagnet yourself by connecting the ends of a copper wire to the
positive and negative ends of an AA, C or D-cell battery. This creates a small
magnetic field. If you disconnect either end of the wire from the battery,
the magnetic field is taken away.
The magnetic field created in this wire-and-battery experiment is the
simple idea behind a maglev train rail system. There are three components to
A large electrical power source
Metal coils lining a guideway or track
Large guidance magnets attached to the underside of the train
The big difference between a maglev train and a conventional train is that
maglev trains do not have an engine -- at least not the kind of engine used to
pull typical train cars along steel tracks. The engine for maglev trains is
rather inconspicuous. Instead of using fossil fuels, the magnetic field
created by the electrified coils in the guideway walls and the track combine
to propel the train.
Above is an image of the guideway for the Yamanashi
maglev test line in Japan.
The Maglev Track
The magnetized coil running along the track, called a guideway, repels the
large magnets on the train's undercarriage, allowing the train to levitate
between 0.39 and 3.93 inches (1 to 10 cm) above the guideway. Once the
train is levitated, power is supplied to the coils within the guideway walls to
create a unique system of magnetic fields that pull and push the train along
the guideway. The electric current supplied to the coils in the guideway walls
is constantly alternating to change the polarity of the magnetized coils. This
change in polarity causes the magnetic field in front of the train to pull the
vehicle forward, while the magnetic field behind the train adds more
Maglev trains float on a cushion of air, eliminating friction. This lack of
friction and the trains' aerodynamic designs allow these trains to reach
unprecedented ground transportation speeds of more than 310 mph (500
kmph), or twice as fast as Amtrak's fastest commuter train. In comparison,
a Boeing-777 commercial airplane used for long-range flights can reach a top
speed of about 562 mph (905 kmph). Developers say that maglev trains will
eventually link cities that are up to 1,000 miles (1,609 km) apart. At 310
mph, you could travel from Paris to Rome in just over two hours.
Germany and Japan are both developing maglev train technology, and both
are currently testing prototypes of their trains. (The German company
"Transrapid International" also has a train in commercial use -- more about
that in the next section.) Although based on similar concepts, the German
and Japanese trains have distinct differences. In Germany, engineers have
developed an electromagnetic suspension (EMS) system, called Transrapid.
In this system, the bottom of the train wraps around a steel guideway.
Electromagnets attached to the train's undercarriage are directed up
toward the guideway, which levitates the train about 1/3 of an inch (1 cm)
above the guideway and keeps the train levitated even when it's not moving.
Other guidance magnets embedded in the train's body keep it stable during
travel. Germany has demonstrated that the Transrapid maglev train can
reach 300 mph with people onboard.
Electrodynamic Suspension (EDS)
Japanese engineers are developing a
competing version of maglev trains that
use an Electrodynamic suspension (EDS)
system, which is based on the repelling
force of magnets. The key difference
between Japanese and German maglev
trains is that the Japanese trains use Japan's MLX01 maglev train
super-cooled, superconducting electromagnets. This kind of electromagnet
can conduct electricity even after the power supply has been shut off. In
the EMS system, which uses standard electromagnets, the coils only conduct
electricity when a power supply is present. By chilling the coils at frigid
temperatures, Japan's system saves energy. However, the cryogenic system
uses to cool the coils can be expensive.
Another difference between the systems is that the Japanese trains
levitate nearly 4 inches (10 cm) above the guideway. One potential drawback
in using the EDS system is that maglev trains must roll on rubber tires until
they reach a liftoff speed of about 62 mph (100 kmph). Japanese engineers
say the wheels are an advantage if a power failure caused a shutdown of the
system. Germany's Transrapid train is equipped with an emergency battery
power supply. Also, passengers with pacemakers would have to be shielded
from the magnetic fields generated by the superconducting electromagnets.
On August 11, 2006, a maglev train compartment on the Transrapid Shanghai
airport line caught fire. There were no injuries, and investigators believe
that the fire was caused by an electrical problem.
On September 22, 2006, a Transrapid test train in Emsland, Germany had 29
people aboard during a test run when it crashed into a repair car that had
been accidentally left on the track. The train was going at least 120 mph
(133 km) at the time. Most passengers were killed in the first fatal accident
involving a maglev train.
The Inductrack is a newer type of EDS that uses permanent room-
temperature magnets to produce the magnetic fields instead of powered
electromagnets or cooled superconducting magnets. Inductrack uses a power
source to accelerate the train only until begins to levitate. If the power
fails, the train can slow down gradually and stop on its auxiliary wheels.
The track is actually an array of electrically-shorted circuits containing
insulated wire. In one design, these circuits are aligned like rungs in a ladder.
As the train moves, a magnetic field the repels the magnets, causing the
train to levitate.
There are two Inductrack designs: Inductrack I and Inductrack II.
Inductrack I is designed for high speeds, while Inductrack II is suited for
slow speeds. Inductrack trains could levitate higher with greater stability.
As long as it's moving a few miles per hour, an Inductrack train will levitate
nearly an inch (2.54 cm) above the track. A greater gap above the track
means that the train would not require complex sensing systems to maintain
Permanent magnets had not been used before because scientists thought
that they would not create enough levitating force. The Inductrack design
bypasses this problem by arranging the magnets in a Halbach array. The
magnets are configured so that the intensity of the magnetic field
concentrates above the array instead of below it. They are made from a
newer material comprising a neodymium-iron-boron alloy, which generates a
higher magnetic field. The Inductrack II design incorporates two Halbach
arrays to generate a stronger magnetic field at lower speeds.
Dr. Richard Post at the Livermore National Laboratory in California came up
with this concept in response to safety and cost concerns. The prototype
tests caught the attention of NASA, which awarded a contract to Dr. Post
and his team to explore the possibility of using the Inductrack system to
launch satellites into orbit.
Maglev Technology In Use
A Transrapid train at the Emsland, Germany test
While maglev transportation was first proposed more than a century ago,
the first commercial maglev train made its test debut in Shanghai, China, in
2002 (click here to learn more), using the train developed by German
company Transrapid International. The same line made its first open-to-the-
public commercial run about a year later in December of 2003. The Shanghai
Transrapid line currently runs to and from the Longyang Road station at the
city's center and Pudong airport. Traveling at an average speed of 267 mph
(430 kmh), the 19 mile (30 km) journey takes less than 10 minutes on the
maglev train as opposed to an hour-long taxi ride. China is building an
extension of the Shanghai line that will run 99 miles (160 km) to Hangzhou.
Construction is scheduled to begin in fall 2006 and should be completed by
the 2010 Shanghai Expo. This line will be the first Maglev rail line to run
between two cities.
Several other countries have plans to build their own maglev trains, but the
Shanghai airport line remains the only commercial maglev line. U.S. cities
from Los Angeles to Pittsburgh have had maglev line plans in the works, but
the expense of building a maglev transportation system has been prohibitive.
The administration at Old Dominion University in Virginia had hoped to have
a super shuttle zipping students back and forth across campus starting back
in the fall semester of 2002, but the train remains motionless while
research continues. The American Maglev Company is building a prototype
using similar technology in Georgia that it plans to finish by fall 2006.