Magnetic levitation trains a trip to the future trains by fwg31028


									                                           Electromagnetism is the main concept behind the functionality of maglev
                                           trains. An electromagnet is defined as just a current-carrying circuit powered
                                           by a battery or another power source. The electric current traveling through
                                           the wire produces a magnetic field around the wire, whose strength depends
                                           on the current’s direction, magnitude, and distance from the current-carrying
                                           wire. Maglev trains use this concept of electromagnetism to propel the train
                                           forward instead of using engines that burn fossil fuels. The train also uses elec-
                                           tromagnetism to lift or levitate the train above a track whose primary function
                                           is to guide the train. Therefore, the three primary functions basic to the maglev
                                           technology are levitation or suspension, propulsion, and guidance [1].

                                           Instead of the typical steel wheel on a steel rail, maglev trains use magnetic
                                           properties to levitate the train above the track or the guideway. The train can be
                                           lifted from 0.39 to 5.0 inches off the track depending on the model of the train.
                                           The maglev trains in Germany use electromagnetic suspension (EMS)
                                           techniques, while those in Japan rely on electrodynamic
                                           suspension (EDS) techniques. The EDS sys-
                                           tems in Japan use super-cooled,

:: Magnetic levitation trains : a trip to the future ::
VanEssa maTsUmOTO / JEssamyn sarCOl / JOnaTHan HaysTEaD / PHilliP ng

                                           superconducting electromagnets [2]. After the power supply has been shut off,
                                           electricity is still conducted through the system. On the other hand, the EMS
                                           system only conducts electricity when the power supply is turned on and as a
                                           result Japan’s EDS system can save energy.

                                           Electromagnetic suspension uses the attractive magnetic force of opposite
Magnetic levitation transportation         poles to levitate the train. Electromagnets on the vehicle interact with and are
is poised as the next generation of        attracted to ferromagnetic rails on the guideway [1]. Two coils, one on the train
high-speed travel. The maglev train        and one in the track, make up the electromagnetic system to levitate this type
can travel at speeds of over 300 mph,      of maglev train. The two coils are attracted to one another when their currents
much faster than the trains currently      flow in the same direction, thereby levitating the train, even when the train is
being used all over the world. Mag-        not in motion [3].
lev trains use electromagnets to pro-
pel the train forward and to levitate      Electrodynamic suspension maglev trains use magnets on the moving train to
the train off the tracks. This use of      induce currents in the guideway using a concept known as electromagnetic
electromagnetism allows the train to       induction. When the train passes over the guideway, superconducting magnets
travel faster than conventional trains.    on the side of the train induce a current on figure 8-shaped coils. What makes
No fossil fuels are needed, and conse-     this system work is the magnets passing below the center of the coil, causing
quently, maglev trains provide a safer     the magnetic flux in the lower half of the coil to be greater compared to the
option for the environment. Finally,       upper half and thereby inducing a current that generates a magnetic force [4].
because the conventional method of         The lower half of the “8”-shaped coil has the same magnetic pole as the super-
steel wheel on steel rail is not used,     conducting magnets on the train while the upper half has the exact opposite
noise caused by the train is greatly re-   pole. Both halves of the train generate an upward component of magnetic force
duced. Currently, Japan and Germany        on the superconducting magnets, which in turn levitates the train. The result-
have the most advanced versions of         ing repulsive force produces inherently stable vehicle support and guidance be-
the train, while the United States and     cause the magnetic repulsion increases as the vehicle-guideway gap decreases
China are also developing their own        [1]. The train must still have wheels in this system because the EDS will not
maglev trains.                             levitate at speeds below approximately 25 mph [1].

Because the train floats on a cushion of air and no friction-    However, even though it is less costly, the linear induction
al force impedes the forward motion, the only force that        motor is heavy and reduces the vehicle payload capacity,
the train has to overcome is air resistance [2]. Due to the     resulting in higher operating costs and lower revenue po-
lack of friction on the tracks and the efficient aerodynamic      tential [1]. e long-stator propulsion system is therefore
design of the train body, maglev trains can reach speeds of     preferred over the short-stator propulsion system.
over 300 miles per hour, which is a little more than half the
speed of a typical commercial airplane.                           e steering of the maglev train is done using the guide-

In addition to levitation, electromagnetism is
used to propel the maglev train
forward. Long-stator

sion uses a linear motor, which is installed in the guide-      way that also houses the electromagnetic coils. In this sys-
way, and functions like a rotating electric motor with the      tem, a computer is used to control the distance between
stator cut open and stretched out below the guideway            the guideway and the train to ensure the ride is smooth
[5]. A magnetic field is generated from the electric cur-        and prevent the train from wobbling around the guideway.
rent in the cable windings that pull the maglev train along     Guideways are usually built on a platform above ground so
the guideway. e moving train with its superconducting           that the maglev train avoids obstacles on the ground. EDS
magnets induces a current on the coils on each side of the      and EMS systems use different types and shapes of the
guideway, producing alternating opposite poles that pull        guideway to optimize for the particular technology used.
and push the superconducting magnets, which then ac-
celerate the train. As the train moves forward, the north       In addition to its high efficiency and speed, maglev tech-
poles switch to south by means of a computer using AC           nology allows for a number of environmental benefits over
current so that the net force is in the forward direction.      other transportation systems. As the human population
   e computer also determines the frequency needed to           continues to grow, the need for a cleaner, safer, and more
switch the poles based on the speed of the train and on the     efficient mass transit system is greater than ever. Traf-
length of the magnets.                                          fic jams, air pollution, and a dwindling supply of natural
                                                                resources are all problems that will only get worse with
   e long-stator propulsion system is also used to bring        time. While no solution completely erases the risks to the
the maglev train to a stop by changing the direction of         environment, magnetic levitation trains offer an approach
the traveling magnetic field, which results in non-contact       with many more benefits than the current systems.
braking of the vehicle because the motor is converted into
a generator [5].      e braking energy is actually fed back     Presently, the most significant threat to the environment
into the power grid in the form of electric energy. Brak-       comes from automobile emissions. e majority of con-
ing of the train is further assured by eddy-current braking     sumer cars operate very inefficiently, and the effects can
magnets in the guideway.                                        be seen hovering over city centers worldwide in the form
                                                                of smog. Also, cars, railroads, and airplanes create copious
Short-stator propulsion is another technique used to move       amounts of noise. Freeways and airports, for instance, can
the train forward.    is system also uses a linear induc-       be heard miles away. Cars and airplanes also create prob-
tion motor winding on the train and a passive guideway.         lems in the political arena, forcing our economy to depend
                                                                heavily on foreign oil.

CEn                                                                                                            spring |
  These problems are not new, but have existed for nearly        joules of electrical power per passenger mile, compared to
  half a century. Past attempts to alleviate these ills have     a 20-mile per gallon car, which consumes 4.0 mega joules
  only succeeded in postponing the matter a few years down       of oil fuel per passenger mile. Because the only form of
  the road. While energy-efficient cars do exist, they simply    friction experienced by a maglev train is due to air friction,
  are not fully ready for the consumer market, and they do       the efficiency can be increased if the train is run through
  nothing in the way of solving traffic problems.                a tunnel or tube that has been depressurized. Under these
                                                                 conditions, the train can operate at what would be equiva-
  Magnetic levitation trains can help reduce all the afore-      lent to 10,000 miles per gallon [8].
                     mentioned issues in an environmen-
                                   tally sound manner.           Not only do maglevs save energy by operating efficient-
                                                 Mag le v s      ly, but their use would result in less energy consumed by
                                                                 other forms of transportation. Assuming the average car
                                                                 runs at about twenty miles per gallon and that every gallon
                                                                 of gas contains 125,000 British Thermal Units (BTUs), the
                                                                 reduction in car trips would amount to a savings of 3.1 bil-
                                                                 lion BTUs per day and 1.1 trillion BTUs annually [9].

  are en-                                                        Another environmental benefit offered by maglev tech-
  tirely    ca-                                                  nology is the absence of waste pollutants produced by the
  pable of adding                                                train. Unlike cars, conventional trains, and airplanes, mag-
  capacity to the national transportation system without         levs run solely on electric power, and as a result no exhaust
  adding to the pollution caused by burning of fossil fuels.     fumes, wastewater, or chemicals are released from a mag-
  The four main environmental benefits of maglev trains are      lev train. The impact of maglev’s non-polluting operation
  summarized as a reduction in energy consumption, harm-         can have a tremendous positive effect on the environment.
  ful emissions, noise pollution, and land usage.                A study done for a proposed maglev train between Balti-
                                                                 more and Washington, D.C. found that the implementa-
  Maglev trains have been called a modern and green mode         tion of such a train could reduce daily automobile trips by
  of transportation [6] due to their extremely high efficiency   18,800 trips. This would mean that the daily amounts of
  and low use of energy. No oil or gasoline of any sort is       Volatile Organic Compounds (VOCs) would be reduced
  needed in their operation, as maglevs run entirely on elec-    by 0.13 tons; carbon monoxide emissions would be re-
  tricity. Compared to a conventional high-speed train, the      duced by 0.60 tons, and nitrogen oxide by 1.44 tons [9].
  same amount of energy input produces a much better per-
  formance. Maglevs are capable of consuming three to five       Although maglevs do not produce any tangible emissions,
  times less energy than cars or airplanes [7].                  they do harness magnetic power, which means a magnetic
                                                                 field would be emitted from the train and the track. The
  Maglevs use what is known as a Linear Synchronous Motor        field created by the track, however, is present for only a
  (LSM) that operates at extremely high efficiencies. Over       short amount of time as the maglev vehicle passes by. The
  ninety percent of the electric power given to the LSM is       field inside and outside the train is no stronger than that
  converted as drive power to the trains. A maglev train run-    of a typical household appliance, such as a television [9].
  ning at 300 mph would be capable of consuming 0.4 mega         No threat is therefore seen towards humans or the envi-

 “. . . superconducting mag-
  nets [induce] a current on
the coils. . . producing alter-
  nating opposite poles that
pull and push the supercon-
          ducting magnets . . .”

ronment due to the maglev’s magnetic field. In fact, it is        references
safe for people with pacemakers, and even mobile phone            	    1.	 “About	the	Orange	Line.”	Orangeline Development Authority.	11	Nov.	2003.	

service is not affected inside an operating train [6].                     Transrapid	International.	16	March	2005,	Online.
                                                                  	    2.	 Bonsor,	Kevin.	“How	Maglev	Trains	Work”		How Stuff Works		24	March,	2005.	Online.	
Freeways, airports, railroads, and other centers of mass         

transportation create tremendous amounts of noise. Mag-           	    3.	 “Levitation	by	attraction”		Maglev Fundamentals 	24	March,	2005.	Online.	http://www.
lev trains, while not silent, are still much quieter than         	    4.	 Sau-ying,	Ma,	Tong	Shiu-sing.	“Maglev”		Physics World 24	March,	2005.	Online.	http://
conventional trains. At 400 km/h, a maglev train will reg-       

ister a noise level of about 90 dB while at 200 km/h, the         	    5.	 California	MagLev	Alliance.	24	March	2005.	Online.
train is virtually silent [6]. Because there is no friction due   	    6.	 Chong’en	Hong.	“Shanghai	Transrapid:	The	technology	is	mature,	safe,	and	reliable.”	
to the track and no engine or brakes to create noise, the                  The	Transit	Coalition.	Online.

only source of noise for a maglev comes from the air be-                   Wu-Wenhui.htm
                                                                  	    7.	 American	Maglev	Technology,	Inc.	(AMT)		“The	Speed	of	Air	Travel	for	Less	Than	the	
ing pushed aside as the train moves along the guideway.                    Cost	of	Travel	by	Car	or	by	Plane.”	Online.
This noise lasts only a few seconds as the train passes by                 technology.htm

and can be reduced with better aerodynamic designs and            	    8.	 Powell,	James,	and	Gordon	Danby.	“Maglev	The	New	Mode	of	Transport	for	the	21st	
                                                                           Century”.	21st	Centruy	Science	and	Technology	Magazine.	Summer	2003.	http://www.2
a special coating on the train’s outer skin. The noise level is  
equivalent to a car traveling at around 70 km/h [7].              	    9.	 Maryland	Transit	Administration	(MTA).	Baltimore-Washington	Maglev	Project	
                                                                           DEIS	Document	Executive	Summary.	March	14,	2005.	Online.	http://www.bwmaglev.
In addition, maglev trains run on elevated tracks and have a      	   10.	 Transrapid	International.	“Transrapid	and	Environment”.	March	14,	2005.	Online.	
very small land footprint. Compared with a freeway, which        

obliterates anything in its path, a maglev track can pass al-
most unnoticed. Consequently, the land underneath the
train guideway can be used for the same purpose as before
the track was built. In this way, farms, grazing grounds,
and protected land can remain virtually untouched.

With their propulsion and lift technology, maglevs can
climb a much steeper slope than conventional trains can.
While conventional trains can only climb a 1-4% grade, a
maglev can climb a 10% grade. Also, due to the inherently
stable function of the magnetic field levitating the train,
the maglev can turn much sharper without fear of derail-
ment [10]. As a result, the landscape does not require as
much change prior to the track’s construction; the maglev
guideway is quite adaptable to wherever type of terrain it
travels across.

Even though the theory of magnetic levitation has been
around for decades, some people are still surprised by
the idea of a floating train. A floating train may exist only
in a science fiction novel to some people, but it is indeed
a reality.

Maglev’s many benefits are far-reaching. The consump-
tion of fossil fuels and the rapid depletion of reserve oil
fields are major problems all over the world. Automobiles
and other modes of fossil fuel-based transportation are
significant contributors to this large amount of fuel-con-
sumption. Furthermore, burning fossil fuel also produces
carbon dioxide and leads to problems such as air pollu-
tion, global warming and ozone layer thinning. Maglev’s
use of electricity is its major advantage in providing po-
tential solutions to these problems. In the absence of such
complications, it is believed that the average American
will not only save time and money by using a maglev train
but will experience reduced levels of fatigue and frustra-
tion associated with driving in congested traffic.

CalEng	                                                                                                                                 2006	spring	|	19

To top