2018-02-13
982
Magnetic Levitation Train or Maglev Train, high speed, ground vehicle levitated above a track called a guideway and propelled by magnetic fields (see Magnetism). Magnetic levitation train technology can be used for urban travel at relatively low speeds (less than 100 km/h, or 60 mph); a short-distance maglev shuttle has been operating in Britain since 19S4j between Birmingham's airport and railway station. However, the greatest worldwide interest is in high speed medley systems: Train speeds of 517 km/h (321 mph) have been demonstrated by a full-size maglev vehicle in Japan.
Two different approaches to magnetic levitation train systems have been developed. The first, called electromagnetic suspension (EMS), uses conventional electromagnets mounted at the ends of a pair of structures under the train; the structures wrap around and under each side of the guideway. The magnets are attracted up towards laminated iron rails in the guideway and lift the train. However, this system is inherently unstable; the distance between the electromagnets and the guideway, which is about 10 mm (3/8 in), must be continuously monitored and adjusted by-computer to prevent the train from hitting the guideway. A 31.5-km (19,6-mi) track in Emsland,Germany, is currently testing this approach.
The second design, called electrodynamic suspension (EDS), uses the opposing force between magnets on the vehicle and electrically conductive strips or coils in the guideway to levitate the train. This approach is inherently stable and does not require continued monitoring and adjustment; there is also a relatively large clearance between the guideway and the vehicle, typically 100 to 15Q mm (4 to 6 in). However, an EDS maglev system uses superconducting magnets, which are more expensive than conventional electromagnets and require a refrigeration system in the train to keep them cooled to low temperatures (see Superconductivity). A 7-km (4-mi) track to test this system, based in large part on designs developed in the United States in the late 1960s and early 1970s, is in use in Miyazaki, in Japan. Both EMS and EDS systems use a magnetic wave travelling along the guideway to propel the maglev train while it is suspended above the track.
Maglev systems offer a number of advantages over conventional trains that use steel wheels on steel rails. Because magnetic levitation trains do not touch the guideway, maglev systems overcome the principal limitation of wheeled trains—the high cost of maintaining precise alignment of the tracks to avoid excessive vibration and rail deterioration at high speeds. Maglevs can provide sustained speeds g reater than 5Q0 km/h (300 mph), limited only by the cost of power to
overcome wind resistance. The fact that maglevs do not touch the guideway also has other advantages; faster acceleration and braking; great climbing capability; enhanced operation in heavy rain, snow, and ice; and reduced noise. Maglev systems are also energy efficient on routes of several hundred kilometres length, they us about half as much energy per passenger as a typical commercial aircraft. Like other electrical transport systems, they also reduce the use of oil, and pollute the air less than aircraft diesel locomotive and cars.
Current plans for high-speed maglev system include a 283-km (175-mi) route from Berlin to Hamburg, which has been approved by the German parliament; commercial operations аre scheduled to begin by 2005. In Japan, a 43-km (27-mi) maglev test track is under construction in Yamanashi Prefecture, about 100 km (60 mi) west of Tokyo. When tests on the latest maglev vehicle have been completed, the test track is planned to be extended to Tokyo and Osaka. This new commercial line will relieve passenger demand on the Shinkansen high-speed train, which currently operates at peak speeds of 225 km/h (140 mph).
In the United States, much of the interest in maglev systems has been initiated at the state level, with plans developed in Florida, California, Nevada, New York and Pennsylvania. Studies completed by the federal government in 1993concluded that the potential benefits of a maglev system justified starting a national development programme.
Bullet Train, popular Western term for Japanese trains. The high-speed rail network is formally known as Shinkansen ("New Trunk Line").
Japan’s national rail system was built in the 19th century. As the country’s economy grew rapidly after World War II, there appeared a demand for transport between Tokio and Osaka. The only satisfactory remedy, the government decided in 1957, was to switch inter-city passenger traffic to a new electrified railway, serving only the ten principal centres between Tokio and Osaka. It would be independent of the historical rail system, and would offer the opportunity for innovative technology that would be able to achieve unprecedentedly high speeds in daily operation. Research advanced so rapidly that construction could begin in April 1959, and the whole 515 km of the Tokaido line opened for business in 1964.
Gentle curves permitted a maximum of 210 km/h. Every axle of each bullet-nosed train was powered for rapid acceleration and sustained high speeds; thus the Tokyo-Osaka trip could be run daily at an average of 162 km/h, inclusive of intermediate stops at Nagoya and Kyoto. This was the world's first trunk railway to dispense with traditional lineside signals. Screens in the trains' driving cabs continuously displayed speed commands picked up from coded electrical signals that were fed through the- rails.
The New Tokaido Line was an instant commercial success; the daily passenger count, averaging 60.000 at the start, had surpassed 200.000 within three years. By 1994 demand required daily operation of 31 Tokyo-Osaka trains in the morning peak, some of them now including double-deckcarriages.
A second Shinkansen, the 563-km (350-.mi) New Sanyo, was completed from Osaka to Hakata, on Kyushu, in March 1975. Subsequent Shinkansen extensions and new train designs have steadily increased "bullet train" speeds. The Tohoku (Tokyo-Morioka) line operates at 240 km/h (149 mph), and the Joetsu (Tokyo Niigata) generally at 240 km/h (149 mph), but in places at 275 km/h (171 mph);. Both were opened in 1882. The latest trains can run at up to 230 km/h (143 mph), and thefastest Tokyo-Osaka schedule has been cut to 2 1/2 hours, representing an average speed of 206 km/h (128 mph). In September 1994 West Japan Railway ordered a prototype able to travel theNew Sanyo at 300 km/h. (186 3/5 mph); and the two other companies operating the high-speed network, Japan Railways Central and East, were each testing train designs with the same capability.
Text 2.
