T Railway Technology Today 12 (Edited by Kanji …jrtr.net/jrtr25/pdf/f58_tec1.pdf · Railway Technology Today 12 (Edited by Kanji Wako) Magnetic Levitation (Maglev) Technologies

58 Japan Railway & Transport Review 25 • October 2000

Technology

Technolo gy

Copyright © 2000 EJRCF. All rights reserved.

Railway Technology Today 12 (Edited by Kanji Wako)

Magnetic Levitation (Maglev) Technologies

The Tokaido Shinkansen began operationsin 1964 and was an immediate success.Since then, Japan’s shinkansen networkhas expanded considerably, and itssuccess has prompted rapid developmentof high-speed railways in other countriesas well, especially in the West.In its early days, the shinkansen was

considered the ultimate form of high-speed rail travel. But passengers in Japannow demand even faster rail service, aswe can see in the preference they haverecently shown for the Nozomi on theSan’yo Shinkansen that runs at 300 km/h,or 70 km/h faster than the older Hikari.The shinkansen uses a conventional train

design, with motors and other equipmentmounted on the rolling stock, electricpower collected from overhead wires, andwheels running on rails. It is extremelydifficult to modify this conventionaldesign to increase speeds much more.Some inherent limitations are:• Greater size and weight of on-board

equipment• Difficulty in collecting electric power• Reduced adhesion between wheels

and rails at higher speeds, causingwheel slip

The shinkansen, and other similar high-

Figure 1 Different Propulsion Methods of Conventional Electric Railways and Superconducting Maglev Guideway

N

N

NS

S

N

S

S

Conventional Railway

Superconducting Maglev Guideway

Pantograph Synchronous motor

Car side

Side wall of guideway

Split open and spread out

On-board electrical equipmentTransformersInverters, etc.

Ground side:Propulsion coils that act like an electric motor armature are mounted in a continuous line on the guideway. The magnetic force on the car side is strong, so the magnetic force on the ground side is weak.

Light, powerful onboard superconducting magnets create a magnetic field like an electric motor.

Transformer stationTransformersInvertersFilters, etc.

1. Superconducting Maglev Developed by RTRI and JR Central

Kazuo Sawada

59Japan Railway & Transport Review 25 • October 2000Copyright © 2000 EJRCF. All rights reserved.

speed trains in different parts of the world,have made rail travel faster than everbefore, but the speed is reaching themaximum poss ib le wi th presenttechnology.To break through this speed barrier, theRailway Technical Research Institute(RTRI) and JR Central are working togetherto develop technologies for a new type ofrailway that is ideal for high speed travel—the superconducting magneticallylevitated train (maglev).

Advantages ofSuperconducting Maglev

Superconducting maglevs are also calledlinear motor cars. The motor is linear, notrotary. We can think of it as an ordinaryelectric motor that has been split open,spread out flat, and oriented in thedirection of train travel (Fig. 1). The motordoes not rotate; instead, it exerts a kineticforce in a straight line, or guideway.One part of the linear motor is mountedon the train, the other on the guideway.The train has l ight but powerfulsuperconducting magnets, and theguideway has energized coils along the

sides. Thus, the train does not carryequipment such as transformers andinverters. As a result, it is very light andslim, but still capable of harnessing a largepropulsive force. Another advantage isthat there are no current collectors andelectromagnetic force levitates thevehicles, so there are no wheels or railadhesion problems.Different types of linear motors have beendeveloped, but the only other type that

supplies electric power to a guideway fortransport is Germany’s Transrapid system.As mentioned, superconducting magnetsare used create a strong magnetic forceto propel the vehicle. But they offer morethan just propulsion—they also levitatethe vehicles and guide them within thebounds of the guideway.The system takes advantage of thenaturally stabilizing effect provided byelectromagnet induction. No controllingdevices whatsoever are needed to keepthe train on its guideway, and there is norisk of the train ‘derailing.’ The magneticlevitation force is ideal for supporting atrain at very high speeds.

Development History

In the early development stages,superconducting magnet technology wasconsidered an esoteric technical field andsome people assumed that the technologycould never be used for commercial traintravel. But the former Japanese NationalRailways (JNR) was convinced that thetechnology held great potential for veryfast rail travel, and began conductingmaglev R&D in 1970.In 1977, experiments began in earnest on

The ML-500 test reached a speed of 517 km/h in 1979 (RTRI)

MLU001 Three-car train on Miyazaki Test Track (RTRI)


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the Miyazaki Test Track in southern Japan.In 1979, the prototype ML-500 test trainreached an unmanned speed of 517 km/hon the 7-km track, proving the maglev’stremendous potential for high speed. Thetrack was modified later into a morepractical U-shaped guideway.At this stage, the Japanese governmentstarted providing the project with financialassistance. The manned MLU001 was thefirst train set developed with governmentsubsidies and had three cars.Soon, the MLU002 and then theMLU002N were being used for a widerange of experiments on the Miyazaki TestTrack. But the test track was too short andonly had a single guideway with notunnels and almost no gradients.Obviously, the experimental data from thetrack would be too limited to verify themaglev’s commercial potential.After JNR was split and privatized in 1987,the Tokaido Shinkansen experienced adramatic increase in passengers, leadingto more calls to build a commercialsuperconducting maglev as soon asfeasible. As a result, the Yamanashi TestLine was constructed in YamanashiPrefecture, 100 km west of Tokyo.

The Yamanashi Test Line

The 18.4-km Yamanashi Test Line supportsa wide range of tests to determine thecommercial viability of superconductingmaglev transport. It was built by JRCentral, which hopes to operate a maglevbetween Tokyo and Osaka, and RTRI,which took over superconducting maglevdevelopment from the former JNR. TheJ a p a n e s e g o v e r n m e n t p r o v i d e sconsiderable financial assistance.Tunnels make up 16 km of the line andthere is one open section 1.5-km longalmost in the middle of the line. Asubstation for power conversion, andother facilities are located at the test centreon the open section. Part of the line isdouble-tracked to simulate actualoperating conditions. This makes itpossible to conduct tests with trainstravelling in opposite directions andpassing each other at high speed. Themaximum gradient is 40 per mill, whileconventional shinkansen lines are 30 permill at most.A total of 7 cars have been developed fortwo train sets. The head cars are 28-m

long, and the middle cars are 22 to 24 m.The 20-tonne cars are only half the weightof the latest shinkansen carriages becausethey use a linear motor system withexcellent propulsive power.Another special feature of the maglev caris the articulated system used to connectcars. We chose this system in order toreduce the height of the carriage body andto facilitate installation of magneticshielding in passenger compartments. Theshield reduces the magnetic field at seatsclosest to the superconducting magnet toabout 4 gauss . For the sake ofcomparison, hospitals recommend 5gauss as the maximum permissibleexposure for a pacemaker wearer.

Results from YamanashiTest Line

Trial runs were begun on the YamanashiTest Line in April 1997. The first train setof three cars was powered by a linearmotor but driven at low speed. In earlytests, the cars were not levitated; instead,they ran on rubber tyres. Once testsverified that there were no defects in thevehicles or guideway, levitation runsbegan at the end of May 1997. Thereafter,speed was increased in very smallincrements over a considerable period oftime, with continual monitoring tomeasure car movement and verify brakingperformance. On 12 December 1997, anew world record of 531 km/h was setfor manned train travel. Then, amaximum speed of 550 km/h wasachieved on 24 December for anunmanned run, thereby achieving one ofthe original objectives of the YamanashiTest Line.Only one problem remains to be solved—air vibration that rattles the windows ofbuildings near tunnel portals when amaglev train enters or leaves a tunnel athigh speed. We are presently attemptingto solve this problem by installing airbaffles at tunnel portals, and by modifyingThis five-car train set registered a record speed of 552 km/h on 14 April 1999 (RTRI)


the opening design (JRTR 22 pp. 48–57).There are no other environmentalp r o b l e m s — g r o u n d v i b r a t i o nmeasurements indicate values well withinacceptable limits and noise levels are alsowithin acceptable limits. Aerodynamicnoise can probably be reduced further bymaking the cars even more streamlined.Measurements of the magnetic field, atground level directly under the standard8m-high elevated guideway show amagnetic field of only 0.2 gauss causedby Maglev trains imposed on the constantterrestrial magnetism of 0.4 gauss.A second train set was completed at theend of 1997, making it possible to conductvarious tests with two trains, such as onetrain passing a stationary train or a trainmoving slowly in the same direction, ortwo trains travelling in opposite directionsat high speed.In February 1999, to more closelysimulate future commercial operations,the 3-car train set was changed to a 5-carconfiguration for performance tests atspeeds in the 500-km/h range. Noproblems were observed and on 14 April1999, this manned 5-car train setregistered a record speed of 552 km/h.In May 1999, the cars were rearranged intheir original configuration of two 3-cartrain sets and high-speed tests arecontinuing to confirm dependability. Thetrains run up to 44 times a day at around500 km/h, and results are good.After reducing aerodynamic vibration inautumn 1999, we conducted high-speedruns on the open section of the guideway.The vibration of trains passing at relativespeeds as high as 1003 km/h was so smallthat it was felt only by someone actuallyexpecting it.

Future Tests

Test runs on the Yamanashi Test Line wereplanned for a period of 3 years (1997–99). No major problem was experienced

during this time, and we have achievedall of our original objectives, including amaximum speed of 550 km/h and relativepassing speeds of 1000 km/h.The Ministry of Transport established theMaglev Technical Performance EvaluationCommittee to verify the technical meritsof the system. The Committee report said,‘Although further study is required toevaluate long-term durability and costeffectiveness, i t appears that thesuperconducting maglev system istechnically ready to be used commerciallyas a very high speed, large-capacitytransportation system.’During the next 5 years we will continueto conduct test runs and develop thesystem further, while focusing on thesethree objectives:• Verifying long-term durability• Finding ways to reduce costs• Achieving more aerodynamic car

design

Conclusion

The superconducting maglev is an entirelynew type of railway that combines thelatest technologies in power electronics(e.g. , superconducting magnets) ,communications and other high-techfields. Maglev development sets a newcourse for rail transport and is a significantmilestone in the 170 years of railwayhistory. Air resistance is the only factorlimiting the speed of this system, so thereis every reason to believe that speeds willbe raised dramatically by, for example,using maglev technology in a vacuum.This innovative made-in-Japan technologyis about to revolutionize train travel forseveral centuries to come. �

Japan and Germany are developingdifferent types of normal-conductivemagnetically levitated linear motor trains.Japan is developing the High SpeedSurface Transport (HSST) system, whileGermany is developing the Transrapidsystem.The two systems are similar in the sensethat they both use linear motors forpropulsion, and electromagnets forlevitation. However, the type of linearmotor used is different.The HSST is propelled by linear inductionmotors. The HSST primary coils are

attached to the carriage body and the trackconfiguration is simple, using steel rails andaluminium reaction plates. On the otherhand, Transrapid trains are propelled by alinear synchronous motor. The motorprimary coils are mounted on theguideway, and the levitation magnets areattached to the car and act as field magnets.These differences can be explained by thefact that in the early development, theJapanese and German systems were notmeant to operate at the same speed. Earlyplans called for the HSST to run at amaximum speed of 300 km/h, although

2. Normal-conducting HSST Maglev

Munenobu Murai and Masao Tanaka


Technology


development efforts are now focusing onintra-urban trains running at about 100km/h. For their part , Transrapiddevelopers are aiming for cruising speedsof 450 to 500 km/h.Since the recent decision to use the HSSTsystem on the Tobu Kyuryo Line in AichiPrefecture, central Japan, this newtechnology is now closer to practicalapplication. Once constructed, the trackwill become the world’s first commercialline. This article briefly explains Japan’sHSST system.

The HSST SystemHSST research began in earnest in 1974when Japan Air l ines ( JAL) beganpromoting a new linear motor car system.At the time, high-speed access betweenTokyo and New Tokyo InternationalAirport (Narita) was considered a matterof priority, because the airport was beingconstructed about 60 km from Tokyo’score. To reduce access time, JAL proposeda maglev train propelled by linear motorsat a target speed of 300 km/h.

Magnetic levitationThe HSST levitation system uses ordinaryelectromagnets that exert an attractiveforce and levitate the vehicle. Theelectromagnets are attached to the car, butare positioned facing the underside of theguideway’s steel rails. They provide anattractive force from below, levitating thecar (Fig. 1).This attractive force is controlled by a gapsensor that measures the distance betweenthe rails and electromagnets. A controlcircuit continually regulates the current tothe electromagnets, ensuring that the gapremains at a fixed distance of about 8 mm.If the gap widens beyond 8 mm, the currentto the electromagnets is increased to createmore attraction. Conversely, if the gapbecomes less than 8 mm, the current isdecreased. This action is computercontrolled at 4000 times per second toensure stable levitation.

As shown in Fig. 1, the levitation magnetsand rail are both U-shaped (with the railbeing an inverted U). The mouths of eachU face one another. This configurationensures that whenever a levitational forceis exerted, a lateral guidance force occursas well. If the electromagnet starts to shiftlaterally from the centre of the rail, thelateral guidance force is exerted inproportion to the extent of the shift, bringingthe electromagnet back into alignment.The use of an electromagnetic attractiveforce to both levitate and guide the car isa significant feature of the HSST system.

PropulsionWe can visualize an HSST linear motoras an ordinary electric induction motorthat has been split open and flattened.This type of linear motor has recently beenused in various fields.

As Fig. 2 shows, in the HSST, the primaryside coils of the motor are attached to thecar body, and the secondary side reactionplates are installed along the guideway.These components act as an inductionmotor, and ensure both propulsion andbraking force without any contactbetween the car and the guideway.The system is called a car-mountedprimary linear induction motor system.The ground side requires only a steel platebacked by an aluminium or copper plate,meaning that the rail structure is simple.

Module structureOne of the HSST’s unique technicalfeatures is its modules that correspond tothe bogies on conventional rolling stock.As Fig. 3 shows, each module consistsprimarily of a number of electromagnetsfor levitation and guidance, a linear motor

Figure 1 Principle of HSST Magnetic Levitation

HSST

SN

Linearmotorcoil

Car body

Airsuspension

Gapsensor

Input signalAmplifier

Levitationmagnet

Cross arm

Rail


Figure 2 Principle of HSST Magnetic Propulsion

Stator(Primary coil)

Rotor(Aluminium cylinder)

Rotary motor

Linear motor

Primary(Coil)

Secondary reaction plate(Aluminium covered rail)

Figure 3 HSST Module Construction

Module frame

Levitation magnet

Linear motor coil

for propulsion and braking, and ahydraulic brake system.The two modules on the left and right sidesof the car are connected by beams, andthis unit is called a levitation bogie.Because the levitation bogies run theentire length of the car, the load of the carand the load on the guideway are spreadout and the advantages of magneticlevitation can be fully exploited.

Advantages offered by HSSTsystemHSST cars do not need wheels and thisoffers a number of advantages that aresummarized below.• Safe

The vehicle is designed so that it‘interlocks’ with the guideway, so thereis no risk of derailment. Theelectromagnetic field level inside thevehicle is no more than that inconventional electric trains.

• Reduced noise and vibrationWhen the vehicle is running there isno physical contact between thecarriages and the guideway whichminimizes rolling noise and vibration.

• Accelerates and decelerates quicklyAcceleration and deceleration can berapid and fairly steep grades can beclimbed easily.

• Low maintenanceThere are fewer moving and rollingparts so wear and tear is less, ensuringeasy maintenance of vehicles andguideways.

• EconomicalThe HSST can operate on fairly steepgradients and tight curves, and thereis no axle load on small spans of track,so guideway construction costs arequite low.


Technology


History of HSST Development

When HSST development began in 1974,research focused on the basic technologyrequired for levitation, propulsion andbraking. In the early days, the target speedwas 300 km/h. A 1.6-km test track wasconstructed on Higashiogishima inKawasaki where the HSST-01 unmannedexperimental vehicle reached a speed of308 km/h. In demonstration runs, the8-seat HSST-02 achieved a maximumspeed of 100 km/h. Some 7 years afterthese development efforts, the basictechnology was recognized as sound.The HSST-03 (1984) was the first to modelto use modules and could carry 50passengers. It showed great promise andcarried more than 1 million passengerswhen demonstrated at The InternationalExposition, Tsukuba in Japan in 1985, andat EXPO ’86 Vancouver in Canada.The HSST-04 was completed in 1988 andran at the Saitama Expo in Kumagaya,Saitama Prefecture. The vehicle ran onan elevated guideway and the VariableVoltage Variable frequency (VVVF)inverter was mounted on the car, insteadof on the ground as in previous models.By this time, it appeared that the HSST

system was ready for commercial use.The HSST-05 composed of two HSST-04cars ran at low speeds at the YokohamaExpo in 1989, although its basic designconcept envisioned a speed of 200 km/h.

HSST-100 Test Track

The basic design of the system up to andincluding the HSST-05 aimed for speedsof about 200 km/h. But the focus changedin 1989 when a project was launched todevelop the HSST for urban transport.Unti l then, researchers had onlydetermined what basic technicalspecifications were required for an HSST-100 vehicle. Under the new project, atest track and vehicles were constructedand test runs were conducted. Theobjective was to determine the practicalityof such a system for mass transit. Theevaluation examined various factors,including safety, reliability and cost.The private Nagoya Railroad Co. Groupin Aichi Prefecture spearheaded theproject . Af ter the Chubu HSSTD e v e l o p m e n t C o r p o r a t i o n w a sestablished in 1989, it was given the taskof testing and developing the HSST-100series. At the same time, the Aichi

prefectural government established acommittee that later issued a reportentitled A Feasibility Study of Urban MassTransit by Linear Motor-Driven Maglev.The committee, chaired by ProfessorEisuke Masada, was composed oft e c h n i c a l e x p e r t s , a s w e l l a srepresentatives from the Ministry ofTransport, the Ministry of Construction,manufacturers and other organizations. Itset out guidelines recommending how thetest track should be constructed and howtrial runs should be conducted, andcarefully scrutinized test results. A widevariety of trials were successfullycompleted, and in 1993 the committeereported that the HSST was sufficientlydeveloped to be used for public masstransit.The test track constructed by Chubu HSSTDevelopment Corporation is 1.5-km longand extends from Oe Station on theChikko Line of Meitetsu in the southernpart of Nagoya City (Fig. 4). The track iselevated, except for about 400-m atground level. To test operations undersuch extreme conditions, it includes asteep grade (70 per mill) and sharp curves.The test vehicles are the two-car 100S and100L built in 1991 and 1995, respectively.Each 100S car has three levitation bogies(6 modules). Car size is about the sameas the new Automated Guideway Transit(AGT) cars such as Yurikamome (JRTR 16,pp. 15–19) that run on rubber tyres. Each100L car has five levitation bogies.Although the 100L is larger than the 100S,the basic configuration is exactly thesame. One reason for developing the100L was to achieve more efficiency withgreater carrying capacity. Table 1 showsthe basic specifications of the 100L andits test track.

HSST-01 experimental vehicle in 1975 (Chubu HSST Development Corp.)


Tobu Kyuryo Line Project

The Tobu Kyuryo Line will extend about9.2 km from Fujigaoka subway station inMeito Ward, Nagoya (Aichi Prefecture)through Nagakute Town to Yakusa Stationon the Aichi Kanjo (Loop) Line in Yakusa-cho of Toyota City.In 1992, the government Council forTransport Policy recommended that theTobu Kyuryo Line be constructed as amedium-weight track, and that the transitsystem for this line be completed by 2008.A committee was asked to recommendwhat type of train should be used and itrecommended a maglev system; thisproposal was accepted in 1999. InFebruary 2000, Aichi High SpeedTransport Inc. was established, and givenprimary responsibility for operating theline. The stage has been set forconstruction and plans call for the line toopen in time for the EXPO 2005 Aichi.The line will extend from Fujigaoka HSST-100L vehicle on elevated test track in Nagoya City (Chubu HSST Development Corp.)

Figure 4 HSST-100 Test Track

R=1500 m

R=1500 m

R=1

00m R=300 m

Platform

Nagoya Loop Road

Meitetsu Chikko LineTo Tokoname

Substation

Meitetsu Tokoname Line

Turnout

Oe Station

To Nagoya

Car Depot

Platform

Control Centre


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Table 1 HSST-100L Test Vehicle and Chubu HSST Development Corp. Test Track

Vehi

cle p

erfo

rman

ce Maximum speedMaximum accelerationMaximum decelerationMaximum deceleration (emergency)Minimum curve radius

100 km/h4.5 km/h/s (with variable load control)4.5 km/h/s (with variable load control)4.5 km/h/s50 m

Car

bod

y

Train setPassenger capacity (head per car)

Car dimensionsWeight of setLevitation and guidance system

Levitation gapElectric motors for propulsionControl unit

Bogie system

Electrical systemService braking systemEmergency braking systemAuxiliary power unitAir temperature controlOperator

2 cars per set68 (33 seated) per car110 per car during peak (0.14 m2 per passenger)Length 14.4 m; width 2.6 m; height 3.2 mAbout 32 tonnes empty (2 cars); 50 tonnes full (2 cars)Maglev system uses attractive force of U-shaped electromagnets for levitation and guidanceMagnetic gap of 8 mm10 Linear induction motors per carVVVF Inverter1560 kVA; 800 A maximumFrequency 0–90 Hz; 1 unit per carModules: 10 modules per car (5 each side)Module pitch: 2500 mm per unit1500 VdcElectric brake; hydraulic brakeHydraulic brakeDC/DC Converter (112 kW continuous rating)Heat pump system for cooling and heatingOne driver

Tes

t tra

ck

Total lengthStandard beam structure

Minimum curve radiusMaximum gradeSwitching mechanism

1.5 kmSingle beams: prestressed concrete beams, steel sleepersMain line, 100 m; turnout, 80 m (equivalent)70%Simple three-segment horizontally rotating switch

Braking system ATS Device

Current collectorRegenerative power absorber

AI/SUS Compound rigid trolley railResistor absorbing with GTO Chopper

Figure 5 HSST-100L Vehicle Design

2500

300 14,400

15,000

30014,400

15,000

600

Mc1 Mc2

Station to Yakusa Station (both stationnames are still provisional) and trains willtake about 15 minutes to travel the 9.2km at a maximum speed of 100 km/h(Fig. 6). Daily passenger density is forecastto be about 30,000.According to the plans, a doubleguideway will serve nine stations(including the two termini) with anunderground section of 1.4 km and asurface section of 7.8 km. The line willbe regula ted by normal ra i lwayregulations and twenty 100L trains will runduring each peak hour.More information on the Tobu Kyuryo Lineproject can be obtained by visiting theAichi Prefecture website at:http://www.pref.aichi.jp/index-e.html

Conclusion

Twenty-five years have passed since theHSST-01 made its first levitated run in1975. The passing years have beencharacterized by repercussions of the twooil crises, Japan’s bubble economy in the

(Unit: mm)


Kanji WakoMr Kanji Wako is Director in charge of Research and Development at the Railway Technical

Research Institute (RTRI). He joined JNR in 1961 after graduating in engineering from Tohoku

University. He is the supervising editor for this series on Railway Technology Today.

Masao Tanaka

Mr Tanaka is Manager in charge of rolling stock at Chubu HSST

Development Corporation. He graduated in electrical engineering

from Nagoya University in 1978 and then joined Nagoya Railroad

Co., Ltd. (Meitetsu) where he worked until 1990.

Munenobu Murai

Mr Murai is Manager of Electrical Systems at Chubu HSST

Development Corporation. He graduated in electronic engineering

from Hokkaido University in 1972 and then joined Japan Air Lines

where he was responsible for development of rolling stock and

electrical systems. He transferred to HSST Development Corporation

in 1986.

Figure 6 Route of Tobu Kyuryo Line

Fujigaoka Station

(Toshokandouri)

(Irigaike)

(Kosenjou) (Geidaimae)

(Maeguma)

(Provisional station names)

(Seishounen-kouen)

(Kagakugijutsu Center)

Yakusa

Station

Higashiyama Line Subway

Higashim

eihan Expressw

ay

Tom

ei Expressw

ay

Nagakute Town

East Nagoya City

To Centre of N

agoya City

Aichi Kanjo Railway

Tobu Kyuryo Line

late 1980s, and recession in the 1990s,but HSST R&D has continued successfully.With the recent decision to use HSSTtechnology on the Tobu Kyuryo Line inAichi Prefecture, the first commercialHSST line will soon be a reality. We mustthank the many people whose years ofeffort will soon bear fruit. �

Kazuo Sawada

Mr Sawada is General Manager of Technology in the Maglev System

Development Department of RTRI. He graduated in electronic

engineering from the University of Tokyo in 1971 and then joined JNR.

He has worked on the maglev project since 1974, holding various

senior posts at the Miyazaki Test Track and RTRI.

Further ReadingJiki fujotetsudo no gijutsu (Maglev Railway

Technology), Masada, Fujie, Kato, Mizuma, Ohmsha,

September 1992.

Documents

T Railway Technology Today 12 (Edited by Kanji …jrtr.net/jrtr25/pdf/f58_tec1.pdf · Railway Technology Today 12 (Edited by Kanji Wako) Magnetic Levitation (Maglev) Technologies