Evaluation of advantages of high-speed EMUs in the case of series 700 Shinkansen high-speed train with IGBT applied traction systems
Yoshiyasu HAGIWARA, Mamoru TANAKA, Masayuki UENO Central Japan Railway Company, Tokyo, Japan
1. Introduction In 1964, Tokaido Shinkansen started the world first revenue service at high speed of over 200km/h. Since then, the Tokaido Shinkansen has demonstrated a successful business of high-speed railway. As a pioneer of high-speed railway, the Tokaido Shinkansen had greatly affected the development of high-speed rail network in Europe. In addition to commercial success, the Tokaido Shinkansen is also proud of its highly reliable operation. In fact, the average delay time per train was only between 0.4 and 0.6 minutes. This statistic figure includes the delay due to natural disasters such as typhoon or earthquake. Therefore, there has been virtually no delay everyday. This punctual operation has been accomplished by good liaison of highly reliable sub-systems. In terms of vehicle systems, power-distributed system, i.e., Electric Multiple Unit (EMU) system, has contributed to the improvement of operational reliability with optimized redundancy and good traction 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, adhesion force utilization, efficient regenerative brake utility, low energy consumption, environmental friendliness, and good traction/braking performance. In contrast, European high-speed trains have mainly employed power-centralized system rather than EMUs. Recently, even in Europe, new power-distributed high-speed trains have appeared, for the purpose of interoperability and operation on steep gradient routes. In fact, German ICE3 started revenue service in 2000, and French AGV is under consideration. In addition, in the process of Taiwan high-speed railway project, the Japanese innovative high-speed series 700 Shinkansen train (Figure 1) successfully won the competition, even in the mood that the team of other countries had great advantage. These recent events have indicated the superiority and good performance of high-speed EMUs. EMUs are becoming the mainstream of high-speed train, not only in Japan but also in Europe. In the past, in spite of a number of merits of the power-distributed system, European railway engineers pointed out its demerits, such as the large amount of maintenance to use electrical equipment in quantities, less comfortable passenger cabin with noise from the underfloor traction equipment, and difficulties of high-speed current collection with plural pantographs. These comments are no longer a truth, and a misunderstanding of the innovative high-speed EMUs in the 1990s. In the 1990s, power electronics technology such as the AC asynchronous motor drive system and advanced material technology such as the large extruded aluminum alloy body construction have been applied to innovative high-speed EMUs in Japan. As a result, energy saving effect by the lightweight train, maximum axle load reduction, good running performance with high adhesion force, high-speed running on steep gradient routes, efficient transport capacity and flexibility of train configuration of EMU with optimum traction performance are noticed and utilized.
1 In this paper, the advantages of EMUs will be examined quantitatively, in the actual case of innovative series 700 Shinkansen high-speed train in Japan. In addition, by focusing on power electronics technology for high-speed EMUs, the effect of application of IGBT to series 700 will be introduced. Moreover, Japanese series 300 and series 700 EMUs and European EMUs, German ICE3, will be compared from the viewpoint of traction system.
Table__Advantages and disadvantages of power-distributed and power-centralized system No. Item Power- Power- Merits of power-distributed system distributed centralized system system 1 Axle load __Reduction construction cost, easier track maintenance 2 Unsprung weight __Good riding quality 3 Traction system __Simple traction system, Installation only underfloor and efficient use of cabin space, effective application of innovative electronics technology 4 Utilization of __High acceleration and deceleration, running on adhesion steep gradients, running on low adhesive conditions with rain or fallen leaves 5 Electric brake __No brake wearing, efficient regenerative brake 6 Changes of MT __Flexibility for operational conditions with ratio optimum traction performance 7 Changes of train __Flexibility for demands with optimum traction length performance 8 Initial cost of train __Reduced by optimizing MT ratio, compensation of initial cost by low running cost 9 Maintenance cost ___ _ Easy maintenance asynchronous motor, good of train life-cycle-cost, no dismantling motor maintenance, contacter-less, maintenance-free traction control system, no brake wearing 10 Comfort of cabin ___ _ Noise reduction measures with IGBT, active suspension control, body structure with noise insulation material 11 Reliability __Optimized redundant system 12 Train weight __Lightweight traction system, Lightweight high power AC motor 13 Transport capacity __No locomotive, all cars with a passenger cabin 14 Current collection ___ _ Reducing of pantographs with high-voltage bus line Note___Excellent, __Good, __Fair, ____Improved for recent EMU with new technologies
2. Comparison of power-distributed and power-centralized systems and examination of advantages of power-distributed system 2.1 Features of power-distributed and power-centralized systems The features of power-distributed and power-centralized systems are listed in Table 1. In the past, as indicated in Table 1, the power-distributed system, EMUs, took advantages of low maximum axle load, good adhesion, running performance and transport capacity, but had problems in comfort, maintenance and current correction at high speed. However, these problems have been dissolved for the recent innovative high-speed EMUs to provide a number of advantages required for high-speed trains. Details of these merits of EMUs will be examined quantitatively in this section.
2 Table 2: Comparison of weight and output power of high-speed trains Power system Power-distributed system Power-centralized system Train type Series 0 Series 700 ICE3 TGV-A ICE1 ICE2 Max. axle load 16t 11.4t 15t 17t 19.5t 19.5t (as series 700:100%) (140%) (100%) (132%) (149%) (171%) (171%) Configuration 16M 12M4T 4M4T M+10T+M M+14T+M M+7T Train length 400m 400m 200_ 240_ 410m 205_ Max. speed 220km/h 285km/h 330km/h 300km/h 280km/h 280km/h Rated output power 11840kW 13200kW 8000kW 8800kW 9600kW 4800kW Train weight 967t 708t 409t 490t 905t 410t
Power/Weight 12.2 18.6 19.6 18.0 10.6 11.7 [kW/t] (66%) (100%) (105%) (97%) (57%) (63%) (Series 700:100%) Motor output power 185kW 275kW 500kW 1100kW 1200kW 1200kW Motor weight 876kg 390kg ------1450kg 1980kg 1980kg Motor power/weight 0.21 0.71 ------0.76 0.61 0.61 [kW/kg] (30%) (100%) (107%) (0.86) (0.86) (Series 700:100%) Motor type DC motor AC AC AC AC AC asynchro- asynchro- synchro- asynchro- asynchro- nous motor nous motor nous motor nous motor nous motor Year of commercial 1964~ 1999~ 2000~ 1989~ 1991~ 1997~ Service
2.2 Weight reduction effect The most important advantage of recent high-speed EMUs is the weight reduction effect. In EMUs, the traction system equipment can be distributed over a train-set, and tractive axles throughout the train-set can obtain the required tractive effort without executing a heavy axle load. As a result, the maximum axle load is reduced. Particularly, recent power electronics technology has realized a lightweight and compact traction system. In the power-centralized system, however, to obtain the tractive effort, the axle load of locomotive must be heavier to avoid slip or skid. Therefore, the innovative lightweight technology is of no use and has to be abandoned. Table 2 shows a comparison of weight and output power of high-speed trains. The maximum axle load of power-centralized system becomes 50% to 70% heavier than that of series 700 Shinkansen EMUs. The Power/weight ratio of a train-set of recent EMUs is around 20kw/t, which is 40% larger than that of power-centralized ICEs and DC motor driven Series 0 Shinkansen trains. In terms of traction motors, the power/weight ratio of AC motor is three times that of DC motor.
2.3 Running resistance The total weight reduction, together with smooth surface of the train and aerodynamic nose shape, contributes to the reduction of running resistance. Figure 2 shows a comparison of running resistance between series 700 Shinkansen train and TGV. In case of TGV, two train-sets are coupled to equalize length of passenger cars of the series 700. From Figure 2, in spite of the wide and tall body cross-section to ensure a large seating capacity, the series 700 realizes low running resistance, compared to that of TGV. That is, Shinkansen provides a high transport volume with low running resistance.
3 2.4 Energy consumption The total weight reduction also contributes to low energy consumption. Lightweight trains can obtain high acceleration from low tractive effort. As a result, energy saving is achieved as the effect of low running resistance and regenerative brake system. Figure 3 shows a comparison of powering and braking energy between series 700 Shinkansen and TGV. Figure 3 is the result of computer simulation of running between Tokyo and Shin-Osaka, which is 515km long, on Tokaido Shinkansen line, at the maximum speed of 270km/h. As a result, the series 700 consumes running energy only 77% of that of TGV.
2.5 Brake energy In terms of brake system, EMUs have a greatly advantage when compared to the power- centralized system. In particular, the AC drive system makes a simple regenerative brake system without brake resistors. Figure 3 also shows the result of computer simulation of brake energy in running between Tokyo and Shin-Osaka. As a result, it has been found that series 700 absorbs braking energy only 74% of that of TGV. In addition to the total brake energy, the modes of braking energy are rather important. In the case of TGV, mechanical brake absorbs 77% of the total brake energy. Therefore, the wear of brake lining requires a large amount of maintenance work. In contrast, in the case of series 700 Shinkansen, motor cars normally use regenerative brake and trailers use eddy current disc brake (ECB), while using mechanical brake only when the speed is 30km/h or lower to stop at a station. As a result, mechanical brake of series 700 absorbs only 3% of the total brake energy. In fact, the average running distance between replacements of brake lining is every 60,000km to 1,000,000km in the case of Tokaido Shinkansen.
4 2.6 Efficient use of adhesion force Because EMUs have a number of tractive axles, they can efficiently utilize adhesion force throughout the train-set. This is the most important factor for good traction performance. To demonstrate the superiority of power-distributed system, the maximum speed, which is limited by the adhesion coefficient and total axle load, is examined under different operational conditions. To simplify the conditions of calculation, assumption is set as shown in Table 3.
Table 3: Assumption for the case study of adhesion force and maximum speed Power-distributed system Power-centralized system Motored car/Trailer 12M4T (M+10T+M)_2 (Model of series 700) (Model of 2 train-sets of TGV) Motored car in a train-set (%) 75% 17%
5 Axle load of tractive axle 11t 17t Number of tractive axles 48 axles 16 axles Total weight of tractive axles 528t 272t Train length 400m 400m Train weight 700t 700t Running resistance Experimental result of series Experimental result of series 700 Shinkansen 700 Shinkansen Adhesion coefficient in dry Used for Shinkansen in dry Used for Shinkansen in dry condition (Figure 4) condition condition Adhesion coefficient in wet Used for Shinkansen in wet Used for Shinkansen in wet condition (Figure 5) condition condition Steep gradient (Figure 6) 3% gradient 3% gradient Failure of a traction unit 25% (3/12) traction down 25% (1/4) traction down (Figure 7)
2.6.1 Efficient adhesion used for highly reliable operation of power-distributed system The power-distributed system contributes to highly reliable operation. To demonstrate this merit, in addition to the considerations of dry condition in Figure 4, gradient resistance is considered in Figure 5; a low adhesion coefficient in wet condition in Figure 6; and failure of traction unit in Figure 7. These results are shown in Table 4. In the dry condition, both systems reach over 300km/h, but in the conditions of wet, steep gradient or failure of traction unit, power-centralized system cannot exceed 300km/h. In fact, the Tokaido Shinkansen takes into account the failure of one traction unit under the wet condition in planning the traction performance. These results demonstrate the high reliability of power-distributed system even in difficult operational conditions.
Table 4: Possible maximum speed in different operational conditions Possible maximum speed Power system Power-distributed system Power-centralized system Dry condition (Figure 4) 480km/h 370km/h Wet condition (Figure 5) 360km/h 280km/h Steep gradient condition of 330km/h 190km/h 3% in dry condition (Figure 6) 1 traction unit failed condition 320km/h 240km/h in wet condition (Figure 7)
2.6.2 Efficient adhesion used for a train-set Figure 8 shows accumulated actual data of occurrences of skid at different axle positions in a train- set. Figure 8 indicates that skid often occurs on front cars rather than on middle or end cars. That is, the expected adhesion coefficient becomes low on the front car. Generally, the power-centralized system has tractive axles in the slippery front car. Therefore, the average adhesion coefficient reduces. Wet condition test of ICE1 (Figure 9) shows that slip often occurs and tractive effort suddenly drops. Therefore, it is supposed that the power-distributed system cannot obtain the expected tractive effort on rainy days.
6 7 3. Elimination of disadvantages of power-distributed system In regard to power-distributed and power-centralized systems, European railway engineers pointed out the demerits of power-
8 distributed system, such as the large amount of maintenance work of traction equipment, less comfortable passenger cabins, and difficulties of high-speed current collection. Recent innovative power electronics technologies have addressed and completely solved these problems.
3.1 Maintenance work reduction of electrical equipment The power-distributed system has distributed power converters and traction motors. In the past, DC motors were used for traction system, which required maintenance of brushes and contactors to require large amount of maintenance work. Recently, however, the innovative power electronics technology has developed the AC asynchronous motor drive system, which has no contactors in convertors or no brushes in traction motors. As a result, problems in maintenance were dissolved. In addition, a non-dismantling inspection line for AC traction motors is used in Japan, and the AC drive system accomplished reduction of maintenance. Moreover, each piece of the equipment of traction system has its own CPU. The monitoring function of operational conditions of the equipment and remote control function are also improved to make maintenance work easier.
3.2 Improvement of comfort of passenger cabin To improve comfort, power electronics and microelectronics technologies apply to the traction system to reduce noise. The lightweight traction system has also contributed to compensating the additional weights of noise insulation and active suspension system, and reduced the weight and improved the comfort of train-set.
3.3 Improvement of current collection in high-speed running In the old power-distributed system, each traction unit has its own pantograph. As a matter of fact, the Series 0 Shinkansen train-set has eight pantographs. Recent Shinkansen trains, however, have a high-voltage bus line through the train-set, which connects the traction system and two pantographs. In addition, the bus system takes advantage of the flexibility of pantograph position in a train-set. In the power-centralized system, the front or end locomotive must be equipped with pantographs, and the noise from the nose section and from the pantograph in use are mixed and increased. Therefore, the flexibility of pantograph position of power-distributed system contributes to reduction the noise outside the train.
4. Technological development of power-distributed system The power-distributed system readily takes advantage of innovation such as electronics technology, and develops according to the advancement of power devices. For example, the series 700 Shinkansen train uses innovative IGBT technology as the world first application to high-speed trains, which improves higher harmonics and noise emission from the traction system by means of higher switching frequency of IGBT and three-level control method.
4.1 Trend of weight reduction and performance improvement by traction system changes Owing to utilizing innovative technologies, weight reduction and performance improvement have been realized for power-distributed systems. To study the effect of lightweight and high efficiency of power-distributed system, traction systems of high-speed Shinkansen trains are compared in terms of systematic weight, power and energy consumption. In this study, the series 100 Shinkansen train represents the DC motor traction system; the series 300 represents the GTO applied AC drive system; and the series 700 represents the IGBT- applied AC drive system.
Table 5: Comparison of weight, rated output and power/weight ratio of traction system of the series 100, 300 and 700 Items Series 100 Series 300 Series 700 Composition of a train-set 12 motored cars and 4 10 motored cars and 12 motored cars and (No. of traction units) trailers 6 trailers 4 trailers (6 units) (5 units) (4 units)
9 a) Traction transformer_kg_ 2600_6=13800 3080_5=15400 3100_4=12400 b) Power convertor (kg) Re:2300_6=13800 2825_10=28250 1660_12=19920 CS:900_6=5400 SL:710_6=4260 Rf: 750_6=4500 c) Traction motor (kg) 820_48=39360 405_40=16200 390_48=18720 d) ECB disc brake (kg) 280_32=8960 245_48=11760 245_16=3920 e) Total weight of 91880 71610 54960 traction system (kg) (e=a+b+c+d) f) Weight comparison 100% 78% 60% among train types (Series 100 = 100%) g) Rated power of 11040 12000 13200 a train-set (kW) h) Power/Weight ratio 0.12 0.17 0.24 (kW/kg) (h=g/e) i) Power/Weight ratio 100% 142% 200% comparison among train type (Series 100 = 100%) Note) Re: Resistor, CS: Controller, SL: Smoothing Reactor, Rf: Rectifier
4.1.1 Effect of weight reduction Table 5 shows a comparison of weight, rated output and power/weight ratio of traction systems of the series 100, 300 and 700. As the series 100 uses a DC motor driven system, a number of components are equipped for the power conversion system and total weight of the system is 92ton. The series 300 employs AC drive systems to realize lightweight and a high power traction system. The total weight is 72ton, which reduces the weight more than 20% when compared to the series 100. The series 300 also employs total weight reduction technologies, such as the extruded aluminum alloy body and bolster-less bogie. Consequently, 25% of total weight of a train-set was reduced to realize service operation at 270km/h. Furthermore, the series 700 succeeded in reducing the weight of traction systems. As a result, 40% of weight reduction and 200% of power/weight ratio are accomplished, when compared to the traction system of the series 700. The weight of traction system of series 700 itself is largely reduced, but the total weight of a train- set is similar to that of the series 300. The reason for this is that the lightweight traction system compensates for the additional weight of countermeasures to improve riding comfort and quietness for passengers, such as noise insulation materials, semi-active anti-vibration controllers and dampers. Figure 10 shows a comparison of weight of Shinkansen trains. For the riding comfort and quietness for passengers, the traction system contributes directly to reducing the higher- harmonics and magnetstrictive noise, and also indirectly to reducing the weight and compensating for the weight increase in the car body.
Table 6: Comparison of energy consumption in running between Tokyo and Shin-Osaka of the series 100, 300 and 700 (including
10 regenerative brake) Items Series 100 Series 300 Series 700 220km/h operation 18.9MWh 16.9MWh 15.2MWh Comparison of energy consumption in 220km/h 100% 89% 80% operation among train types (Series 100 =100%) 270km/h operation ------21.2MWh 19.4MWh Comparison of energy consumption in 270km/h ------100% 92% operation among train types (Series 300 =100%)
4.1.2 Effect of higher efficiency Table 6 shows a comparison of simulation results of energy consumption in running between Tokyo and Shin-Osaka of the series 100, 300 and 700. Because of the improved efficiency of traction system, reduction of running resistance and effectiveness of utility of regenerative brake by 12 motored cars, energy consumption is improved by 20% when compared to the series 100, and by 10% when compared to the series 300. This contributes to the reduction of running cost in the long run.
4.2 Japanese and German power-distributed systems, series300, series700 Shinkansen train and ICE3 Recently, to adapt to interoperability and steep gradient running, the innovative power-distributed train, German ICE3, appeared in Europe. In terms of composition of traction systems, the system of ICE3 is similar to that of series 300 Shinkansen train. Figure 11 summarizes trajectory of the changes in the train concept and systems from series 0 Shinkansen to German ICE3, including ICE1, ICE2, and series 300 and series 700 Shinkansen trains in the chronological order.
11 4.2.1 Comparison of traction systems
12 Figure 12 also compares traction systems of ICE3 and series 700, based on that of series 300 Shinkansen train. The traction unit composition of ICE3 resembles that of series 300, with three cars, two motored cars and one trailer (M1, Tp, M2). To make the best weight balance in a train-set and to reduce the maximum axle load, heavy electrical equipment, one traction transformer and two traction converters are mounted on three different cars. As for 700 series, to reduce the cost and total weight, the number of traction unit is reduced to four from five of the series 300. The traction unit of series 700 is composed of four cars, three motored cars and one trailer (T, M2, M’, M1). Like in the series 300, heavy electrical equipment is mounted on different cars to ensure weight balance and a low axle load. That is, M1 car has one converter; M’ car has one traction transformer; M2 car has two converters, and T car has auxiliary circuit equipment. A traction transformer has three secondary winding traction circuits, and each circuit connects
PWM convertor and PWM inverter, then parallel four traction motors are driven. The rated output
13 of a traction motor is 275kW (Figure 13). Both the PWM convertor and PWM inverter apply three-level control method. Both the pressed package type IGBT and module type IGBT are used for the power converter. Specifications of the power converter are 1,220V of input voltage, 1,030A of input current, 1,500Hz of career frequency
and 2,400V of DC stage voltage.
4.2.2 Comparison of traction performance As shown in Table 2, the power/weight ratio of train-set is examined in Figure 14. In the case of ICE3, the power/weight ratio increased to almost 20kw/t, which is close to the levels of series 300 and 700. It seems that power/weight ratio of 20kW/t is a standard level of current high-speed EMU, but is almost twice that of power-centralized ICE1 and ICE2.
14 5. Conclusion To demonstrate the superiority of power-distributed system, EMUs, this paper examined weight reduction effect, environmentally friendliness, energy saving effect and good traction performance with efficient use of adhesive force. As mentioned above, to realize highly reliable high-speed and high frequency operation over 300km/h, the power-distributed system will be the best solution. From this study, following results are induced. (1) Recent high-speed EMUs take advantages of low maximum axle load, lightweight, good adhesion utilization, efficient regenerative brake, low energy consumption, environmental friendliness, and good traction/braking performance. These features are suitable and required for high-speed trains. (2) Because of the application of AC drive system, recent high-speed EMUs have solved long- lasted problems in maintenance work, passenger comfort, and current collection. Therefore, EMUs are now evaluated better than in the past. (3) The power electronics technology realizes high-power, lightweight and compact traction system. The power-distributed system readily realizes the merit of new technologies. As for the power-centralized system, locomotives become heavier to avoid slip or skid. Consequently, lightweight systems are of no use. (4) From the viewpoint of adhesion performance, in dry condition, there are no practical differences in the traction performance between power-distributed and power-centralized systems. Operation at the speed over 300km/h is possible. (5) In contrast, in wet condition or steep gradient condition, it is difficult for the power- centralized system to operate at the speed over 300km/h. (6) The power/weight ratio of the latest high-speed train is around 20kW/t, and Japanese series 300 and 700 and German ICE3 have reached this level. (7) The power electronics technology will continuously advance in the future. The power- distributed system will enjoy the merits of innovation and will improve according to the innovative electronics technologies. (8) For highly-reliable, high-frequency, high-speed operation at the speed over 300km/h, the power-distributed system is the best solution
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