INVESTIGACIÓN CON RESPECTO AL TEMA

DE ELECTROMAGNETISMO

HOW maglev trains

work

Elaborada por:

MARTÍNEZ RAYA Edgar Gerardo

Semestre 2010-2

INTRODUCTION

TO 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 or weeks.

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.

Electromagnetic Suspension (EMS)

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 this system:

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 combines 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 forward thrust.

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 kph), 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 kph). 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 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 kph). 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.

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 desig ned

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

stability.

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

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.

SOURCES

Magnetically Levitated Train Takes Flight - October 2004

http://science.howstuffworks.com/framed.htm?parent=maglev-

train.htm&url=http://www.llnl.gov/str/October04/Post.html

China's Maglev Train Line "Sinking" - 05/13/04

http://science.howstuffworks.com/framed.htm?parent=maglev-

train.htm&url=http://news.bbc.co.uk/2/hi/asia-pacific/3711031.stm

Shanghai Supertrain Makes First Journey - 12/31/02

http://science.howstuffworks.com/framed.htm?parent=maglev-

train.htm&url=http://news.bbc.co.uk/2/hi/asia-pacific/2616339.stm

Trains Reach High Speeds With Magnets

http://science.howstuffworks.com/framed.htm?parent=maglev-

train.htm&url=http://www.techtv.com/news/culture/story/0,24195,3370193,00.html

Transrapid International

http://science.howstuffworks.com/framed.htm?parent=maglev-

train.htm&url=http://www.transrapid.de/en/index.html

Is Magnetic Levitation Possible?

http://science.howstuffworks.com/framed.htm?parent=maglev-

train.htm&url=http://hepweb.rl.ac.uk/ppuk/PhysFAQ/levitation.html

Overview of Maglev R&D

http://science.howstuffworks.com/framed.htm?parent=maglev-

train.htm&url=http://www.rtri.or.jp/rd/maglev/html/english/maglev_frame_E.html

Maglev Transportation System at Old Dominion University

http://science.howstuffworks.com/framed.htm?parent=maglev-

train.htm&url=http://faculty.washington.edu/jbs/itrans/odumag.htm