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[Kahaner:26] Bullet-train technology 2 of 2
From: David Farber <farber () central cis upenn edu>
Date: Wed, 28 Dec 1994 03:25:45 -0500
occurring, especially when the vehicles pass through tunnels, and the influences of forces acting on the body will become increasingly greater as the train speed becomes higher. If the car body expands or contracts when running, passengers would feel uncomfortable and the vehicles would undergo rapid fatigue, resulting in a deterioration of car body strength. To prevent these problems, the car bodies must have an airtight and rigid structure with minimal expansion and contraction. Aluminum alloy structural members have been used for this purpose. [This is quite similar to constraints associated with aircraft body construction.] The car body framework, almost identical to that of a house, essentially consists of pillars and main beam members, which are reinforced with small beams, and mounting flooring and body shell. In the 0-series and 100-series cars, steel plates of 2-3mm thickness serve as the pillars to provide the structural strength, and steel plates of about 1.6mm thickness are mounted on the pillars. With the 200-series cars designed for the frigid environment in the northern part of Japan, additional equipment and body mount covering structures down to the floor are required, making the body heavier. To achieve weight reduction, aluminum material is used but the basic structure remains the same as previous models. With the "Nozomi" 300-series, thick beams have been eliminated and a new structure, in which the structural strength is sustained by the structure made of thin structural members, has been introduced reducing the body weight to 6.0tons. The 200-series body weighs as much as 8.5tons. What made this structural renovation possible was the remarkable progress achieved in aluminum extrusion technologies, which allows extruding aluminum into structural members of required shape and size usable as large plates required for Shinkansen car bodies. The large extruded plates (with a thickness of 2.2mm, width of 600mm and height of 15-25mm and the same length of 24.5m as that of the car body) are shaped with longitudinal structural members installed at a spacing of 80-100mm. These plates are welded together to make principal structural members of the car body. The walls formed with these thin extruded aluminum plates provide the overall structural strength by its finely tuned structure, so the fabrication of these walls requires precision machining technology. At Kasado Works, assembly of these precision structural members is being conducted by the advanced machinery manufacturing technologies fostered through years in the manufacture of trains. The plates produced in conformance with fixed specifications of about 25m long and 60cm wide has enabled automatic welding in some parts of the assembly process since welding can be performed in a straight line. Automation not only improves the strength but also reduces the costs of manufacturing these structural members. * Truck The truck is another key component which mounts the wheels, motors, brakes and shock absorbers necessary for running on the railway, and supports the car body weight. It serves to transmit the forward advance motions of the wheels revolved by the motor to the body, controls the oscillations generated by the rails and maintains good riding comfort. With the 0-series the truck weighs 19.1tons, and with the 100-series 9.8tons. With the 300-series trains, whose top priority had been to achieve maximum lightness, the bolsterless structure was introduced and weight reduction of 30% was achieved. The bolster is a large beam installed at the central part of the truck frame, and serves to absorb the oscillations between the car body and the truck. The development of the pneumatic spring has made oscillation prevention possible without using the bolster. When a train travels at curved sections, it can pass these curved parts more smoothly if the truck has greater flexibility. However, the movement of the long and rigid carriage body is largely restricted, so the truck has to cope with the constraints of the body. If the truck was overly flexible, it would generate oscillations by itself, prompted by diverse factors on straight track, which lead to dangerous zigzag running movement. Therefore, running stability at high speeds and stable performance when traversing curved tracks had to be realized in concert with body lightening. The levels of the longitudinal and lateral stiffnesses and other values were studied in details at the design stage through computer simulation. Meeting these requirements, the "Nozomi" train bolsterless truck (with an oscillation absorption system based primarily on the air spring) has been developed. Also, wheel diameter has been reduced to 86cm, smaller than that of other series. In addition, the axle was changed from the conventional rod type to bored type, and the gear case and axle box changed to aluminum. * Driving and control system Each carriage of the 0-series train has 4 sets of motors, the train uses a total of 64 sets of motors, and the total output is 11,840kW. With the 100-series train, 48 motors are used and the total output is 11,040kW. The motors used through the 100-series trains were DC, and the 100-series motor, which is lighter than that of 0-series, weighs 825kg. With the "Nozomi," which demands higher power for running at a faster speed, an AC motor was introduced to meet the requirement without increasing the weight. The rotational speed of DC motor can be altered by changing the voltage, so it has a simple structure and is easy to control. Its weak point is that brushes (which are heavy and require regular inspection and replacement) have to be used to transmit electricity to the rotator. An AC motor uses no brush, but since it is essentially a mechanism that revolves in conformance with the current frequency, its accurate control at high speeds is quite difficult. However, progress in the pulse width modulation (PWM) inverter has enabled stable control and a larger capacity. The inverter serves to convert DC current into AC current, and can set the frequency flexibly. Hitachi has the typical PWM inverter for the large power electric carriage motors, the variable-voltage, variable-frequency (VVVF) system that can flexibly change not only frequency but also voltage. A semiconductor system known as the gate turnoff (GTO) thyristor is used to turn on and off large currents of several hundred amperes as rapidly as in a millionth of one second, and the repeated ON-OFF generate the necessary frequency. The development of equipment which can withstand high voltages and large capacities through these new technologies led to the realization of the AC motor drive system (3 phase asynchronous motor and powering circuit equipment) for use on the "Nozomi" train. The compact high-power motor of "Nozomi" requires a high level of rotational speed, but weighs only 390kg, has output 300kW, and revolves at 5,470/minute. * Regenerative braking When power feed to motors is terminated during train operation, the motors are kept revolving by the wheel rotation and become a sort of electric current generator. With conventional driving systems, this current is passed through resistors for dissipation as thermal energy. However, the electromotive force becomes increasingly larger with high-power motors for high-speed trains, making the resistors needed for heat dissipation increasingly larger, conflicting with the weight reduction requirement for high-speed electric vehicles. A regenerative braking system has been designed to eliminate the use of resistors. The electricity generated by the motors is raised to a voltage of over 25,000V and returned to the catenary line through the pantograph for use by other nearby electric cars or for return to the substation to comprise an energy conservation system. Various undesirable influences would be exerted on power networks if AC currents of inappropriate phases are returned to the power networks, so the AC electricity generated by the motors is first converted temporarily into DC current with a converter, then reconverted into AC current of the same frequency and phase as those of the catenary line through an inverter. The complicated controls of these inverters and converters are performed using advanced microcomputer technologies. The recent remarkable progress in semiconductor and electronics technologies, especially large-capacity semiconductors, has been indispensable for "Nozomi". In addition, the control functions of these drive systems are linked to the central Shinkansen operating systems, safety control systems and maintenance & inspection control systems to comprise an integrated overall system. * Train nose shape The train nose shape affects the air resistance. The CD value is used to represent this state, and the smaller this value, the less the air resistance. The CD value is 0.15 with the 100-series and 0.11 with the 300-series. That of an ordinary passenger automobile is 0.3-0.5, and that of a racing car 0.2-0.4. * Pantograph The 300-series trains use only three pantographs, two of which are actually used when running and the other used mostly as a spare. In contrast, the 0-series trains use 8 pantographs, while the 100-series trains use 6 pantographs. The number of pantographs is decreased to reduce the noise generated through the pantograph's contact with the catenary line and through its friction with the air. To prevent air-friction noise, a cover is used for the pantographs. HITACHI'S KASADO WORKS Kasado Works started manufacturing railway vehicles in 1921 by manufacturing steam locomotives and in 1924 completed the country's first large-sized electric locomotive, after which it engaged in the manufacture of various innovative types of railway vehicles such as monorail cars and linear motorcars. It completed the first Shinkansen train in 1963, and has delivered a total of 1,060 trains by the end of 1993. The "Nozomi" train production started in 1991. The fabrication of "Nozomi" starts with the assembly of aluminum structural members, and the car body structure and truck are produced through diverse subsequent operations such as welding. The truck is fitted with motors, and the car body mounted on these trucks. After this, the seats and interior furnishings are installed in the passenger coaches. The completed vehicles are then inspected to confirm the functions and performance of the braking and electrical systems, then hoisted with cranes equipped in the port of the works and loaded onto ships for transportation over the Seto Inland Sea to rolling stock bases. The Kasado Works manufactured the 200-series Tohoku and Joetsu Shinkansen line trains in 1963, and is presently manufacturing a new model "MAX." By drawing on its most advanced technologies, in 1993 it completed fabricating the next-generation Shinkansen experimental trains, "STAR 21 " for East Japan Railway Co. and "WIN 350" for West Japan Railway Co. At present, it is also manufacturing the 30OX train that is the next-generation model of the "Nozomi" for Central Japan Railway Co. The factory is also engaged in the manufacture of products other than railway rolling stock, such as chemical plants and semiconductor manufacturing systems. Underpinning its activities which extend over diverse sectors of industry are its advanced technologies for designing and manufacturing large-sized structures such as pressure vessels and vacuum equipment, supported by its precision machining technologies. Other products include the helium-cooled systems supporting superconducting technology and the artificial satellite vacuum testing system in the field of space development, all of which are typical of the most advanced modem technologies. CAR BODY AIRTIGHTNESS & FATIGUE TESTING FACILITY At the Kasado Works is a massive facility to test airtightness strength for confirming the safety of "Nozomi" carriages, particularly for its pressure resisting strength when passing through tunnels. This facility consists of a tank with a diameter of 5m and length of 30m as well as a pressurizing and depressurizing tank for rapid pressurization and depressurization, also compressors for pressurization and vacuum pumps for depressurization. The tank proper is capable of accommodating a "Nozomi" car intact, so the influences exerted on the car when it passes through tunnels, or the most severe conditions when running at superhigh speeds, can be simulated. In the testing of "Nozomi" body, pressurization to 3.7kPa and depressurization to -7.4kPa at a cycle of 45 seconds are repeated for three months (based on the values obtained through research studies) by which accelerated deterioration is obtained as if the vehicles ran for 15 years, leading to the confirmation of the strength and safety of "Nozomi." The Kasado Works is situated in Kudamatsu City, Yamaguchi Prefecture, has a labor force of 1,500 employees, a land area of 538,000m^2 and a floor area of 206,000m^2. * Kasado Works, Hitachi, Ltd. 794 Higashitoyoi, Kudamatsu-shi, Yamaguchi Prefecture 744 Japan Tel: +81-833-41-0123 Fax: +81-833-41-8683 NEW TYPE OF TRAIN RUNNING AT 300km/hr West Japan Railway Company (JR-West) has announced it will fabricate a train consisting of a new type of vehicle (500 Series) which will be capable of running at a commercial speed of 300km/hr. The train is to be completed in autumn next year [1995], commissioned into service as a special train in the spring of 1996, and can be manufactured by a mass production line. The railway company conducted running tests on the test train WIN350 from June 1992, and acquired good results for commercialization based on the test performances of riding comfort and environmental measures for noise reduction. The train is to consist of 16 coaches, and up to 1,323 passengers can be accommodated in ordinary coaches and special luxury "Green Cars." These coaches are smoothed and designed as a wing shape for weight reduction, while the leading coach has a long, sharp shape, and the pantograph is designed for suppression of aerodynamic noise to eliminate environmental problems accompanying the increased speed. An aluminum honeycomb material featuring excellent noise-shielding effect is used, and active suspensions are used to minimize vehicle vibration. The design concept is based on the long-nose design commensurate with high-speed running, and aims to achieve functional excellence and aesthetic form. The train manufacturing cost is roughly 4.5 billion Yen. By commercial operation at a speed of 300km/hr, the same as that of the French TGV system, the aim is to shorten the 2 hrs and 32 min required for travelling the distance between Shin Osaka and Hakata stations to 2 hrs and 19 min, a reduction of 13 min. JR-West plans to continue further tests on the WIN350 system and to commission the special train into service in the spring of 1996 with the aim of putting the train into full-scale operation from the spring of 1997. West Japan Railway Company (JR-WEST) Public Relations Dept., 4-24, Shibata, 2-chome, Kita-ku, Osaka 530 Japan Tel: +81-6-375-8889; Fax: +81-6-376-6053 ---------------------------END OF REPORT-----------------------------
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