Abstract-- This paper presents advantageous features of the distributed traction systems, or Electric Multiple Units, and application of power electronics technology to the Shinkansen High-speed train. The EMUs have many advantages such as the energy saving by regenerative brake, high-speed running on steep gradient routes with high adhesive force, and others. Historically, the Japanese high-speed train system, Shinkansen, has employed the EMU system, and furthermore, it has adopted the AC regenerative braking system and the asynchronous motor driving system for the traction system since the Series 300 in 1990. The current flagship Series N700 Shinkansen train employs the train-draft-cooling power converter with the low-switching-loss IGBT. This contributes to realizing a quarter of weight/power ratio of the traction system and a half of energy consumption, compared with the Series 0, the first-generation Shinkansen. In this paper, as a future development of innovative lightweight technologies, a permanent magnet synchronous traction motor (PMSM) is also introduced.

Index Terms-- Power converter, permanent magnet synchronous traction motor (PMSM), Shinkansen, traction system.

I. INTRODUCTION

In 1964, the commercial service of the Tokaido Shinkansen (bullet train) was inaugurated as the world’s first high-speed train operating at more than 200 km/h. Since then, the Tokido Shinkansen has demonstrated its success as a high-speed rail (HSR) business. As a pioneer of HSR, the Tokaido Shinkansen has greatly affected the development of the HSR network in Europe. In addition to its commercial success, the Tokaido Shinkansen boasts its highly reliable operation. The average delay time per train has been maintained at less than 1 min over the past 15 years. This statistic includes delays attributed to natural disasters caused by such as typhoons, earthquakes and so on, which means that there are virtually no delays every day. This punctual operation has been accomplished by excellent linkage of highly reliable subsystems, including hardware and software. In respect to vehicle systems, distributed traction systems, that is, electric multiple unit (EMU) systems, have contributed to the improvement of operational reliability through optimized redundancy and good traction performance thanks to higher adhesion performance. Historically, the Japanese high-speed train system, Shinkansen, has employed the EMU system, which has a number of advantages, such as maximum axle-load reduction, adhesive force utilization, efficient regenerative brake

utility, low energy consumption, environmental friendliness, and good traction and braking performance. In contrast, European high-speed trains have mainly adopted the concentrated traction system, or the locomotive system, rather than the EMU system. In the past, European railway engineers regarded inherent superiority of distributed traction systems as disadvantages because multiple electrical equipment required large amount of maintenance work and noises from under-floor traction equipment degraded comfort in passenger cabins. However, these thoughts are no longer valid and could be relegated into the category of misunderstanding in regard to the innovative high-speed EMUs, adopting enhanced power electronics technology after the 1990s.

Power electronics technology has played an important role in improving the speed and achieving weight reduction since conception of the Shinkansen high-speed EMU in the 1960s. Power devices for power converters have evolved, as the thyristor adopted at initial stage was replaced by the gate turn-off (GTO) thyristor and the insulated gate bipolar transistor (IGBT) is in the current mainstream. Also, traction systems have evolved from the direct current (DC) drive to the alternating current (AC) drive, consequently improving the total performance of the traction system. Especially in 1990, power electronics technologies, such as the power converter with GTO thyristor, the AC asynchronous motor drive system, and the AC regenerative braking system were applied to the Series 300 Shinkansen train, which was the first application for HSR in Japan and also all over the world. Furthermore, the weight/power ratio of the latest Series N700 Shinkansen train as a trainset achieves half that of the Series 0 Shinkansen train, although the maximum operational speed has increased from 210 km/h to 300 km/h [1]. Recently, even in Europe, new high speed trains with distributed traction systems have appeared for the purpose of interoperability and operation on routes with steep gradients. These high speed trains utilize much of power electronics technology. Germany’s InterCity Express (ICE3) started commercial service in 2000, and France’s Automotrice Grande Vitesse (AGV) is also preparing for its commercial debut. These recent events have proven the superiority and good performance of high-Speed EMUs [2-4].

This paper presents advantages of EMUs and introduces the current flagship Series N700 Shinkansen high-speed train in Japan to examine the features of EMUs. We describe innovative lightweight technologies,

Traction Systems Using Power Electronics for Shinkansen High-speed Electric Multiple Units

Kenji Sato*, Masakatsu Yoshizawa*, and Takafumi Fukushima** *Technology Research and Development Department, General Technology Division, Central Japan Railway Company

1545-33 Ohyama, Komaki, 485-0801 Aichi, Japan** Rolling Stock Department, Shinkansen Operations Division, Central Japan Railway Company

Marunouchi Chuo Bild.,1-9-1 Marunouchi, Chiyoda-ku, Tokyo 100-0005, Japan

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978-1-4244-5393-1/10/$26.00 ©2010 IEEE

such as power converters with train-draft-cooling and the permanent magnet synchronous traction motor (PMSM), focusing on power electronics technologies for high-speed EMUs. Furthermore, we discuss contribution of lightweight technologies to lower energy consumption attained by the latest Shinkansen high-speed trains. In conclusion, this paper reevaluates the EMUs’ advantages such as the energy effect of lightweight trains, maximum axle-load reduction, good running performance with high adhesive force, high-speed running on steep gradient routes, efficient transport capacity, train configuration flexibility, and optimum traction performance.

II. COMPARISON OF DISTRIBUTED TRACTIONSYSTEM AND CONCENTRATED TRACTION

SYSTEM

A. Features of Distributed Traction System and Concentrated Traction System

In general, the traction systems of high-speed trains can be categorized into two types in terms of power distribution: the distributed traction system and the concentrated traction system. Figure 1 shows the example of those systems. The distributed traction system is represented by the electric multiple unit (EMU) system, in which a trainset has several electric units composed of several motor cars, in some case, with one or more trailers. On the other hand, the concentrated traction system is represented by the locomotive system, in which a trainset has one or more locomotives to pull or push the trailers.

:Passenger car

:Powered axle

Distributed Traction System

Concentrated Traction System

CI : Power ConverterMTr : Traction TransformerMM: Traction Motor

An Electric Unit

14 Motor Cars2 Trailers

2 Locomotives8 Trailers

MM

MM

Fig. 1. Example of Distributed Traction System and Concentrated Traction System.

B. Superiority of Distributed Traction System The features of the distributed traction system are

listed as follows. In the past, it was considered that the distributed traction system, or the EMU system, had advantage of low maximum axle loads, good adhesion, traction performance, and transport capacity, but was inferior in regard to comfort, maintenance, and current collection at high speeds. However, these problems have

been solved with recent innovation carried out for high-speed EMUs. Table I shows the comparison of weight and power output of high-speed trains [1-6].

Merits of the distributed traction system are as follows.

1) Effective use of regenerative brakes: The distributed traction system has a great advantage over the concentrated traction system in respect to the braking system. The AC drive system makes possible a simple regenerative braking system without brake resistors. Table II shows results of a computer simulation of braking energy when operating between Tokyo and Shin-Osaka [1]. Each value of energy/seat in Table II is converted in terms of the Series 300’s powering energy/seat, which is set as “100.” This indicates that the Series 300 uses only 54% of the braking energy needed by the TGV-A. Also, the method of braking is rather important. In the case of the TGV-A, mechanical brakes absorb 77% of total braking energy. This leads to a large amount of maintenance work needed for worn brake linings. In contrast, with the Series 300 Shinkansen, motor cars normally use regenerative brakes, and trailers use eddy current disc brakes. Mechanical brakes are used only at speeds of 30 km/h or lower to stop at a station. As a result, mechanical brakes on the Series 300 absorb only 3% of total braking energy. Brake linings are replaced on average every 1 million km of operation on the Tokaido-Sanyo Shinkansen.

2) Higher acceleration and deceleration performance resulting from greater total load on powered axles: The acceleration and deceleration performances are affected by the adhesion between wheels and rails. If the acceleration or deceleration force on an axle exceeds the adhesion performance of its axle load, slips or skids can occur. Since the distributed traction system has more powered axles and higher total load on powered axles than the concentrated traction system, it is possible to set lower acceleration or deceleration forces per axle but to obtain higher traction performance in total. Figure 2 shows comparison of tractive acceleration between Shinkansen (Series N700) and TGV-POS [5]. The merits of higher acceleration and deceleration performance are short acceleration/deceleration distance and ability of ascending steep gradient, which enables shorter travel time.

3) Effective use of space above the floor for passenger cabins: While passenger cabins are hardly deployed on locomotives for the concentrated traction system, with the distributed traction system the space above the floor can be fully utilized as passenger cabins to yield more passenger capacity because its electrical equipment is mounted under the floor.

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TABLE ICOMPARISON OF WEIGHT AND OUTPUT OF HIGH-SPEED TRAINS

Power System

Distributed Traction System Concentrated Traction System

Train Type Series 0 Series 300 Series 700 Series N700 ICE3 AGV TGV-A TGV-POS ICE2

Max.axle load (t) (as Series 300:100%) 16 (140%) 11.4 (100%) 11.4 (100%) 11.2 (98%) 15 (132%) 17 (149%) 17 (149%) 17 (149%) 19.5 (171%)

Train configuration 16M 10M6T 12M4T 14M2T 4M4T 6M5T M+10T+M M+8T+M M+7TTrain length (m) 400 400 400 400 200 200 240 200 205Max. speed (km/h) 220 270 285 300 330 -- 300 320 280Rated power (kW) 11,840 12,000 13,200 17,080 8,000 9,400 8,800 9,280 4,800Train weight (t) 967 711 708 715 465 416 484 423 422

Train power/ weight (kW/t; as Series 300:100%)

12.2 (72%) 16.9 (100%) 18.6 (110%) 23.9 (141%) 17.2 (102%) 22.6 (134%) 18.2 (108%) 21.9 (130%) 11.4 (67%)

Motor output power (kW) 185 300 275 305 500 760 1,100 1,160 1,200

Motor Weight (kg) 876 390 390 394 -- 730 1,450 -- 1,980

Motor power/ weight (kW/kg; as Series 300:100%)

0.21 (27%) 0.77 (100%) 0.71 (92%) 0.77 (100%) -- 1.04 (135%) 0.76 (99%) 0.61 (79%)

Motor type DC motor AC asynchro-nous motor

AC asynchro-nous motor

AC asynchro-nous motor

AC asynchro-nous motor

AC syncronous motor (PMSM)

AC synchro-nous motor

AC asynchro-nous motor

AC asynchro-nous motor

Power device of power converter

-- GTO IGBT IGBT GTO IGBT Thyristor GTO GTO

Year of commercial service

1964 1992 1999 2007 2000 -- 1989 2007 1997

M = motor car; T = trailer car; -- = data unavailable; TGV-A = Train à Grande Vitesse Atlantique; AGV = Automotrice à Grande Vitesse

TABLE IICOMPARISON OF POWERING AND BRAKING ENERGY

Series 300 TGV-A

Powering energy / seat 100 (Regenerated brake power is deducted from total coonsumpution) 158 Series 300:TGV = 63%:100%

Braking energy 2.49 4.63 Series 300:TGV = 54%:100% Electric brakes / seat 2.41 (97%) 1.06 (23%)

Regeneratibe brakes: 1.54 (62%) Dynamic brakes: 1.06 (23%)Eddy current brakes: 0.86 (35%) (No regenerative brake equipped)

Mechanical brakes / seat Mechanical brakes: 0.09 (3%) Mechanical brakes: 3.57 (77%)

Running pattern: From Tokyo to Shin-Osaka, 515.5 km long; stops at Nagoya and Kyoto, maximum speed of 270 km/h.Train condition: Series 300: configuration: 10M6T, length:400 m, weight: 768 t; capacity: 1323 seats. TGV: configuration: (M + 10T + M) * 2, length:240 m * 2, weight: 490 t * 2; capacity 485 seats*2.

Each value of energy/seat is converted in terms of the Series 300’s powering energy/seat. ( The Series 300’s powering energy/seat is set as "100.")

4) Reduction in maximum axle load: Lower maximum axle load with averaged load distribution can optimize infrastructures and reduce construction costs.

Demerits believed in the past are as follows.

1) Noise in passenger cabins due to equipment under floor: As higher-frequency-switching power devices and a three-level control method had been developed, noise caused by switching harmonics was drastically decreased. Moreover, new noise blocking techniques such as noise-proof floors also effectively contributed to noise reduction.

2) High initial cost: The recent widespread use of the AC asynchronous motor drive system and the AC regenerative braking system brought down cost of electrical equipment.

Fig. 2. Comparison of Tractive Acceleration of Distributed Traction System and Concentrated Traction System.

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III. TECHNICAL INNOVATION OF TRACTIONSYSTEMS FOR TOKAIDO SHINKANSEN EMUS

A. Improvement of Rolling Stock Performance To enhance passenger service and strengthen

competitiveness against other transportation modes such as airlines, JR Central is steadily promoting measures to increase train speed, reduce travel time and reinforce transport capacity. JR Central raised the maximum train speed (which was 220km/h with the Series 0 and the Series 100) to 270km/h with the Series 300. The maximum speed of the Series N700 in the Tokaido Shinkansen is 270km/h, however, the speed on curves with a radius of 2,500m has been raised from 250km/h to 270km/h owing to the newly-equipped body inclining system. In the Sanyo Shinkansen, the maximum speed is 285km/h with the Series 700 and 300km/h with the Series N700 as shown in Fig. 3.

Fig. 3. Transition of the Tokaido Shinkansen Rolling Stock.

B. Effects of Traction System Change on Shinkansen High-Speed EMU

The Shinkansen EMUs readily take advantage of innovations in power electronics technology, and they develop according to the advancement of power devices. For example, the Series 300 used GTO thyristors to realize an AC drive system in 1990, and in 1997 the Series 700 became the first high-speed train in the world to use innovative IGBT technology. In addition to improving train performance and giving birth to lighter and more compact traction system, these technological innovations have reduced the high harmonics and noise emitted from the traction system by means of the higher switching frequency of IGBT and a three-level control method.

Since the Series 100 uses a DC motor-driven system, it requires a number of components, such as a resistor, a smoothing reactor, and a rectifier, for the sake of power conversion, which results in a total system weight of 92 tones. The Series 300 employed the AC drive system using GTO thyristors for the first time, resulting in a traction system that was lighter and high powered. The total weight is 72 tons, 20% less than that of the Series 100. The Series 300 also employed total weight reduction technologies, such as an extruded aluminum alloy body and bolsterless bogies. Consequently, total trainset weight

was reduced by 25%, realizing service operation at 270km/h. The Series 700 succeeded in reducing the weight of the traction system, and the total weight is 55 tons. Further weight reduction of the traction system was carried out for the Series N700, while increasing its power output. As a result, the weight-power ratio of its traction system in a trainset achieved a quarter of that of the Series 0. Figure 4 shows trends in the weight-power ratio of the traction systems of Shinkansen trains, from the Series 0 to the Series N700. Thus, systematic change of the traction system has contributed to realizing powerful, lightweight, and efficient traction systems for high-speed EMUs.

Fig. 4. Trends of Weight of Traction System per Power in a Trainset (as Series 0: 100).

C. Traction System of Series N700 Two types of electric units compose the traction

system of the Series N700: four-motor-car units and three-motor-car units. Figure 5 shows the circuit diagram representing the composition of the four-motor-car units. The conversion system of the Series N700 employed the innovative lightweight technology, “Power Converter with Train Draft Cooling System.”

In general, forced-ventilation-cooling systems can downsize traction equipment such as traction transformers, traction motors, and power converters, and traction equipment in turn has its own blower motors and fans for cooling. In particular, due to the large amount of traction power needed as the Shinkansen runs at high speeds, an extraordinary amount of dissipative heat is produced by traction equipment and must be somehow released. Therefore, until recently it was thought that the use of power converters with train-draft-cooling, i.e., self-cooling systems, was impossible for the Shinkansen high-speed train, even though self-cooling inverters were quite practical for the traction system of conventional line trains and the auxiliary power supplies. However, thanks to the advent of new IGBT with lower switching loss and analysis of airflow under the floor at high speeds, the use of power converters with train-draft-cooling systems on Shinkansen trains entered the realm of possibility [7]. Train-draft-cooling power converters are advantageous in that they are lighter in weight since cooling blower motors, fans and liquid cooling mediums are not required.

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Tractionmotors

Power Converter

Main converter

Ground brush

High voltage train lineVacuum circuit-breaker

Traction trans-former

Arrester

Power Converter Power Converter

Power Converter Tractionmotors

Tractionmotors

Tractionmotors

Ground brush

Ground brush

Ground brush

Fig. 5. Circuit Diagram of Traction System for Four-motor Car Units of the Series N700.

(a) (b) Fig. 6. (a) Power Converter with Train Draft Cooling System for Series N700, (b) Power Converter Mounted under Body of Series N700.

0

10

20

30

40

50

60

70

80

90

100

0 300 600 900 1200 1500 1800 2100 2400Time [s]

Tem

pera

ture

[deg

]

0

30

60

90

120

150

180

210

240

270

300

Trai

n Sp

eed[

km/h

],Air

spee

d[m

/s],IS

/IM[*

10A

]

COV-IGBT tempINV-IGBT tempCooling air tempCooling air speedISIMTrain speedTrain speed*22%

Fig. 7. Running Test Results of Power Converter with Train-Draft-Cooling System.

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Moreover, their simple structure, which does not comprise the cooling medium and cooling system, will contribute to easier maintenance, higher reliability, cost-reduction, eco-harmony such as reduction in green-house effect gases. On these backgrounds, we developed train-draft-cooling power converters for the Shinkansen high-speed train, which was the first application in the Shinkansen history .

The prototype of the train-draft-cooling power converter was mounted on the Series N700, and running tests were carried out. The prototype is shown in Fig. 6. Figure 7 shows running test results of the train-draft-cooling power converter on the Series N700. Regardless of changes in train speeds, we confirmed that sufficient speed of cooling airflow was available (more than 22% of the train speed on average). The running tests also showed that the temperature increase seen in each part of the power converter was well below temperature limits.

As a result of the above development, the Series N700 commercial fleet was fitted with train-draft-cooling power converters, and 8 power converters out of 14 in a trainset are now of the train-draft-cooling variety. The weight reduction effect of the train-draft-cooling power converter is shown in Fig. 8. The weight-power ratio of the train-draft-cooling power converter is half that of the power converter of the Series 300 in 1990.

0

20

40

60

80

100

Series 300 Series 700 Series N700 (Train-draft-cooling)

Weight of power converter/Output power

Fig. 8. Comparison of Weight to Power Ratios of Power Converters (as Series 300: 100).

D. Energy Saving Due to Traction System Changes The energy consumption mainly depends on the

running resistance, the weight of a trainset, the efficiency of electrical equipment and the performance of regenerative brakes. From this viewpoint, it is important to reduce weight as well as increase the performance of regenerative brakes. Figure 9 shows the comparison of energy consumption by different types of Shinkansen high-speed trains. The Series N700 consumes energy equivalent to approximately half that consumed by the Series 0 in running at 220km/h between Tokyo and Shin-Osaka. This energy saving is achieved by the running resistance reduction, the weight reduction and the effective application of regenerative brakes.

Fig. 9. Comparison of Energy Consumption of Shinkansen Trains (as Series 0: 100).

IV. FUTURE DEVELOPMENT OF TRACTION SYSTEMS

Aiming at lighter-weight and more energy-saving traction system, JR Central is now developing a permanent magnet synchronous motor (PMSM) as a future alternative (Fig. 10) [1]. The lightweight PMSM has been developed in these ways.

1) Design concept for the innovative lightweight PMSM is following:

-Pursuing optimal performance by choosing a permanent magnet with the highest BH max; -Alleviating increase in temperature by selecting proper number of poles; -Pursuing lighter weight by employing forced-ventilation to cool motors; -Same electrical specifications as those of the asynchronous motor of the Series N700.

2) Test results for the lightweight PMSM are as follows. Figure 11 shows test results for the overall characteristics of the lightweight PMSM. Results indicated that required torque and power were obtained, and measured terminal voltage and phase current almost matched those of designed values.

3) To evaluate the weight reduction effect, the weight-power ratios of traction motors on high-speed trains are compared in Table III [1,2,8]. While around 1.30 kg/kW are the standard value of traction motors on resent high-speed trains worldwide, the lightweight PMSM marks 0.90 kg/kW, which seems to be the world’s lightest traction motor for application in high-speed trains. The lightweight PMSM also showed 5% higher efficiency compared to the equivalent asynchronous motor. Our simulation to run trains with PMSM between Tokyo and Shin-Osaka revealed that energy consumption was reduced by around 7%. At next stage of our research, we will focus on application of new power devices such as SiC and also cost-reduction measures of power conversion systems for the PMSM.

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Fig. 10. Comparison of Conventional Traction Motors with Lightweight PMSM for Shinkansen Trains.

Fig. 11. Test Results Overall Characteristics of PMSM.

TABLE IIICOMPARISON OF WEIGHT AND OUTPUT OF TRACTION MOTORS FOR HIGH-SPEED TRAINS

LightweightPMSM

Series 0 Series 300 Series N700 FASTECH360S

ICE1 TGV-A AGV

Motor power output (kW) 305 185 300 305 355 1,200 1,100 760

Motor Weight (kg) 276 876 390 394 440 1,980 1,450 730Weight/ power (kg/kW) 0.90 4.74 1.30 1.29 1.24 1.65 1.32 0.96

Motor type PMSM DC motor Asynchronous motor

Asynchronous motor PMSM Asynchronous

motorSynchronous motor PMSM

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V. CONCLUSIONS

The distributed traction system, or the EMU system, has many advantages, such as the energy saving by efficient regenerative braking, maximum axle-load reduction, good running performance with high adhesive force, high-speed running on steep gradient routes, efficient transport capacity, and train configuration flexibility. Historically, the Japanese high-speed train system, Shinkansen, has employed the EMU system. Technological development has been continuously pursued since the inauguration of the Tokiado Shinkansen in the 1960s. The development of the Series 300 in 1990 represents a major breakthrough in rolling stock technology. Taking advantage of the enhanced power electronics technology, we have pioneered practical application of the power converter with GTO thyristor, AC regenerative braking system and the asynchronous motor driving system for the traction system of the Series 300. This contributed to the lightweight traction system with increased output, which led to 270 km/h operations of the Tokaido Shinkansen. Since then, we positively employed evolution of the power electronics technology to make the traction system more efficient and lighter weight. We applied the train-draft-cooling power conversion system with the low-switching-loss IGBT to the latest Shinkansen train, the Series N700 in 2007. As a result, the Series N700’s weight/power ratio of the traction system in a trainset is a quarter of that of the Series 0, the first-generation Shinkansen train. In addition, the Series N700 consumes energy equivalent to approximately half energy that consumed by the Series 0 in running at 220km/h between Tokyo and Shin-Osaka. This energy saving was achieved by the running resistance reduction, the weight reduction and the effective application of regenerative brakes. The

Shinkansen EMUs are continuously evolving with the introduction of innovative power electronics, such as new power devices and PMSMs, into the next stage. We are seamlessly aiming for further improvement of rolling stock performance, passenger comfort, reliability of operations, reduction in maintenance work and lower energy consumption by utilizing power electronics technology.

REFERENCES

[1] Y. Hagiwara, S. Ishikawa, M. Furuya, “Innovative Lightweight Technologies Using Power Electronics on Shinkansen High-Speed Electric Multiple Units,”Transportation Research Record, Journal of the Transportation Research Board, No.1995, pp. 43-51, 2007.

[2] “Alsotom unveils its new high-speed multiple unit, the AGV,” Railway Update, pp.68-71, February 2008.

[3] Wolfram, M., and R. Theo., ICE High-Tech on Rails, 3rd

ed., Hestra-Verlag, 1996, pp. 172-176. [4] David Briginshaw “AGV: the next generation,”

International Railway Journal, pp. 23-26, March 2008. [5] “TGV POS PREPARES to enter service,” Railway Gazette

International, pp. 783-784, December 2006. [6] Brian Perren, TGV HAND BOOK, Capital Transport

Publishing, 1993, pp.109-112. [7] M. Ueno, T. Fukushima, K. Sato, “Development of Train-

Draft-Cooling Power Converters for the Shinkansen High-Speed Train,” The International Symposium on Speed-up, Safety and Service Technology for Railway and Maglev Systems 2009 (STECH’09), Niigata (Japan), June 2009.

[8] R. Furuta, Y. Yasui, S. Shiraishi, A. Yajima, H. Yamamoto, “Development of Permanent Magnet Synchronous Motor Drive System for High Speed Train over 400km/h Speed” (in Japanese), The 17th Transportation and Logistics Conference 2005, pp. 91-92, Kawasaki (Japan), December 2005.

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