Maglev Program in Korea

Cho, Hung-je, Sung, Ho-kyung, Kim, Bong-sup Lee, Jong-min, Yoo, Munhwan

Korea Institute of Machinery and Materials Yoosung-ku, PO box 101, Daejon, Korea

Phone : 82-42-868-7198 , e-mail : cho_hj@kimm.re.kr

Abstract Maglev Project Team at KIMM has been leadingdevelopment of attraction type urban transitmaglev for the past 10 years. In this papercurrent status of maglev program in Korea - whathas been done so far, efforts to improve technicalproblems we have – is reported.

1. General

Maglev Project Team at KIMM(Korea Institute ofMachinery and Materials ) has been leadingdevelopment of EMS type urban maglev for thepast 10 years under the sponsership of the ministryof science and technology. In June 1998 we , incooperation of Korea Railway Manufacturingcompany, introduced two vehicle consisted maglevtrain - UTM-01. Running test of UTM-01 forthe past three years confirmed the basicperformances of the maglev train but showedmany improvements yet to be made forcommercial applications. Overall system reliabilityfalls short of expectations and refinements ofeach sub-systems have to be made. It was the firstmaglev train we made and these were expected. We believe that as far as the EMS system isconcerned once the levitation can be secured, it canbe one of the promising urban transportationsystems and that many of the commercialmaglev lines appear worldwide in the near future. Recently the Korean government granted us a 4year project to build a new version of twovehicle consisted maglev train. In this paper wereport what we are doing to develop animproved maglev model UTM-02 .

2 . UTM-01

Fig 1 shows UTM-01 under test . Therepresentative vertical gap records are shown inFig. 2. Peak to peak

of gap fluctuations is 2.5 mm at 40 km/h. Itoccurs at rail joints. Noise level in dbA was

measured in the car when accelerating at the rateof 0.8 m/

2s. Maximum noise level was about 72

dbA.

Figure 1. UTM-01 under running test

Figure 2. Representative vertical gap

Running tests for the past 3 years identified manyimprovements yet to be made. They are :(1) Need to reduce peak to peak of gap

fluctuations occuring when dual gap sensorspass the rail joints. Also fail safe of thelevitation controller has to be providedthrough dual mode.

(2) Short radius curve (less than 40m radius ofcurvature ) negotiability has to be improved.

(3) Need to improve Linear Motor efficiency.(4) Noise reduction of the major power supply

equipments such as VVVF, DC/DC converter.(5) Need to reduce total weight of the train. (6) Automatic Train Control is a must.

3. Development Plan of Light RailType Maglev UTM-02

In what follows we describe what we have beendoingto improve UTM-01.

Levitation Controller

Levitation controller in EMS systems is a key tocommercialization . It is an inherently unstablesystem , so there is no way to maintain nominalgap clearence for all cases . There could be amoment for the magnet to hit the rail due tounusually big gap fluctuations when mechanicallybraking on 7 % downslope with high speeds. Wethink the controller will suffice so long as it isrobust enough to return to normal controlimmediately after the magnet hits the rail. Asidefrom the robustness , we need to secure thelevitation for possible hareware failures related tothe levitation – failure of part of gap oracceleration sensors, magnet drivers, and controlleritself. Duality of magnet drivers is provided.Duality of controller is not yet done and wehave to do for the coming years. Figure 3 ,4shows the test data of the fault tolerant control(FTC) aganist part of the gap or accelerationsensor failures[1]. It is seen that stable levitationis maintained even if part of the gap oracceleration sensors fails.

Carbody

Present car's cabin floor height above the reaction

plate is 1080 mm. In UTM-02 it is reduced to 870mm to give a low center of gravity for better runningperformance against external disturbances. Carbody consists of three bogies and is supportedby 6 air springs – one for each side frame of thebogie just likeconventional wheel on rail bogies. It is simple buthas difficulty in negotiating tight curve less than 50

Figure 3. Gap signal when part of the gap sensorsfails

Figure 4. Gap signal when part of theacceleration sensors fails m radius of curvature. In UTM-02 , the airspring at the center bogie is designed to beconnected to the carbody via linear bearing sothat the carbody and the center bogie slide througheach other to avoid excessive deflection of the airspring in the lateral direction. Bogie The length of the bogie in longitudinal direction isreduced from 3.5 m to 3.0 m for better curve andup/down grade running performance. The weightof the newly designed bogie is 2.2 tons comparedwith 3 tons previously. The emergency landingroller was modified so that the train can bereturned to the maintenance shop or sideway bythe LIM or another tugging car when thelevitation fails on tight curve. Linear Induction Motor

5 10 15 20 259

10

11

12

13

ga

p [

mm

]5 10 15 20 25

-0.4

-0.2

0

0.2

0.4

acc

[m

/s2]

5 10 15 20 255

10

15

20

i 11 [

A]

5 10 15 20 255

10

15

20

i 12 [

A]

time [sec]

5 10 15 20 25 309

10

11

12

ga

p [

mm

]

5 10 15 20 25 30-0.1

-0.05

0

0.05

0.1

acc

[m

/s2]

10

12

14

i 11 [

A]

i 12 [

A]

The efficiency of the newly designed LIM wassomewhat improved as follows. - by allowing larger current density.- by using smaller slip frequency than ever

In doing so, design optimization was done withcurrent density , temperature ,and weight of theLIM as parameters . Figures 5 shows test data ofthe LIM at the rotary LIM tester.

Figure 5. LIM test data compared withcalculations. In table 1. major specifications of the newlydesigned LIM were compared with those of theUTM-01's. Description UTM-01 UTM-02 maximumthrust

3.3 KN 4.5 KN

max. currentdensity

4.1 A/2mm

5.5 A/2mm

operating slipfrequency

12.5 Hz 10 Hz

material AL AL Length 2.3 m 2.3 m max.acceleration

0.8 m/2s

1.0 m/2s

weight 250 kgf 190 kgf Table 1. Major Specifications of UTM-01 and 02 Major power supply equipments Major power supply equipments such as VVVFInverter, DC/DC converter, Magnet Drivers , andL&G Controller are being developed with thefollowing points in mind.

(1) All of these use natural cooling to reduce fannoise

(2) Carrier switching frequency above 2 KHz toreduce noise drastically.

(3) Reduce weight of each equipments by 30 % ormore and ease of maintenance.

(4) Operating temperature range between -25and + 80 degrees in Celsius.

Figure 6 shows test data of the noise level of the

Figure 6. Experimental data of the noise levelof the VVVF Inverter with differentswitching frequencies.

VVVF Inverter at different switching frequencies.It is seen that at switching frequency 2.5 KHz ,the noise level is 59.4 dbA. The VVVF andDC/DC converter are being developed withswitching frequencies to be above 2 KHz.

Magnet UTM-01 used general structural steel for bothmagnet yoke and poles. In UTM-02 , pure ironwas used for yoke and general structural steel forpoles. Anodized aluminium sheet was used for coil. Themagnet was made smaller and lighter resulting inratio of levitation force vs. magnet weight from8.46 previously to 9.86 with increased nominalcurrent from 19 A to 24 A. Figure 7 shows experimental data on levitation force withincreasing magnet current.

0 3 6 9 12 15 18 21 24 27 300

1000

2000

3000

4000

5000

Thru

st [N

]

slip frequency [Hz]

-4000

0

4000

8000

12000

16000

Norm

al fo

rce [N

]

10 20 40 80 160 315 630 1250 2500 5000 1000020

30

40

50

60

70

SP

L (

dB

at

1 m

ete

r)

Hz

sf=400 Hz: 63.5dBA sf=800 Hz: 64.8 dBA sf=1000 Hz: 64.4 dBA sf=1500 Hz: 64.4 dBA sf=2500 Hz: 59.2 dBA Background Noise: 58.4 dBA

Figure 7. Levitation force with magnet currents Power Collector Figure 8 shows the newly designed powercollector. Test confirmed smooth operation with muchlower contact noise and good power collectingcapabilities.

Figure 8. Newly designed power collector Test Track Maglev test track is located at our institute (KIMM) in city of Daejeon . The length is 1.3km. It has 6 % gradient, 60 m radius ofcurvature curve , and switching facility. Allowablemaximum speed on the 650 m straight section is

70 km/h. The switching facility is of a parallelmoving type, which also needs redesigning withshorter switching time in less than 25 seconds.Right now it takes 80 seconds. Table 2 shows major specifications of UTM-02compared with those of UTM-01. Major Spec. UTM-01 UTM-02 dimension 13.6m *3m

*3.96m 13m*2.8m*3.6m

empty weight 22 tons 14 tons maximumcapacity

80 persons 64 persons

max. speed 100 km/h 100 km/h Levitationgap

11 mm 10 mm

No. of bogies 3/car 3/car max.acceleration/deceleration

0.8 m/2s

, inemergency1.25 m/

2s 1.0 m/

2s , in

emergency 1.25m/

2s

vvvfswitching frequency

500 Hz 2000 – 2500Hz

dc/dcswitching freq.

400 Hz 2000 Hz

curvenegotiability

60 m radiusof curvature

less than 30 mradius ofcurvature

power supply DC 1500 V DC 750 V ATO no yes Table 2. Major specifications of UTM-02 Time Schedule of the light rail type MaglevUTM-02 Time schedule for UTM-02 is By the end of 2003 ;

- finish development of major power supplyequipments

- secure more robustness of L&G controllerand find a way to manipulate double gapsensor signals at 45 mm rail jointsmaximum.

By the end of 2004 ,- finish designing prototype maglev ,

hopefully to be accepted as a commercialmodel .

By the end of 2005 , - finish manufacturing two vehicles- finish developing ATO

0 4 8 121620242832364044485256606402468

101214161820222426

Initial LevitationNominal Levitation

Levi

tatio

n F

orce

[kN

]

Magnet Current [A]

calculated(10mm) tested(10mm) calculated(18mm) tested(18mm)

In 2006 :Performance test and evaluation

Conclusion

Though small in scale , maglev project in Koreahas been progressing continuously for the past 11years.

By virtue of the commercialization of Nagoyaand China transrapid lines, the Koreangovernment and several regional states arebeginning to show strong interest in maglev. Korea is a very populated country . The traffic isvery much congested in every big cities. Subwaysystem costs too much, and so the governmentdeclared that they wouldn't construct subway anymore and that all the public transportationsystems to be built from now on would be lightrail systems. Therefore commercialization ofmaglev is thought to be a matter of time, once wecan assure maglev is a safe, environmentallyfriendly alternative .

References

1. Sung, Ho-kyung, " A study on the design ofrobust and reliable controller for electromagneticsuspension system " , ph. D. thesis, KoreaAdvanced Institute of Science and Technology,1991 .

2. Kim, in-kun,et al " Maglev program in Korea " ,1993, 1995, 1998 , 13 th, 14 th, 15 th InternationalConference on Magnetically Levitated System.