MAGLEV ( Magnetic Levitation Train )

Magnetic Levitation Train, also maglev train, a high-speed ground transportation vehicle levitated above a track called a guideway and propelled by magnetic fields. Magnetic levitation train technology can be used for urban travel at relatively low speeds (less than 100 km/h, or less than 62 mph). For example, a short-distance maglev shuttle operated for 11 years from 1984 to 1995 between the Birmingham, England, airport and the city train station. However, the greatest worldwide interest is in high-speed maglev systems. Train speeds of 552 km/h (343 mph) have been demonstrated by a full-size maglev vehicle in Japan, while in Germany a maglev train has run at 450 km/h (280 mph) and in China a maglev train has reached a peak speed of 432 km/h (268 mph).

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 either side of the guideway. The magnets attract up toward 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 track 31.5 km (19.6 mi) long in Emsland, Germany, was used extensively to test this approach. As a result of these tests, the German government granted a commercial license to Transrapid International (TRI), a company headquartered in Berlin, Germany, to develop maglev systems based on the EMS design.
The second design, called electrodynamic suspension (EDS), uses the opposing force between superconducting magnets on the vehicle and electrically conductive strips or coils in the guideway to levitate the train. This approach is inherently stable, and it does not require continued monitoring and adjustment. There is also a relatively large clearance between the guideway and the vehicle, typically 100 to 150 mm (4 to 6 in). However, the EDS maglev system uses superconducting magnets, which are more expensive than conventional electromagnets and require a refrigeration system in the train to keep the superconducting magnets cooled to low temperatures (see Superconductivity). A 7-km (4-mi) test track for this design, based in large part on designs developed in the United States in the late 1960s and early 1970s, was built in 1977 in Miyazaki, Japan, by the Railway Technical Research Institute, a Japanese firm. Both EMS and EDS systems use a traveling magnetic wave 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. Maglev trains can provide sustained speeds greater than 500 km/h (300 mph), limited only by the cost of power to overcome wind resistance.
Because maglev vehicles do not touch the guideway and therefore encounter no friction, they can achieve faster acceleration and braking; greater climbing capability; enhanced operation in heavy rain, snow, and ice; and reduced noise. Maglev systems are also energy efficient. For distances of several hundred miles, they use about half the energy per passenger as a typical commercial aircraft. Electrified transportation systems, such as maglev systems, also reduce the use of petroleum and pollute the air less than aircraft, diesel locomotives, and automobiles (see Air Pollution).
A Transrapid maglev system began service in January 2004 in Shanghai, China, connecting the city to the Pudong International Airport. The train conveys passengers over the 32-km (20-mi) route between downtown and the airport in 8 minutes, compared with 30 minutes by automobile. Additional plans for high-speed maglev systems include two lines within Germany: one an 80-km (50-mi) route between Düsseldorf and Dortmund and the other a 30-km (20-mi) connector linking Munich to its airport.

In Japan, a 43-km (27-mi) maglev test track was built in 1996 in Yamanashi Prefecture, about 100 km (62 mi) west of Tokyo. If the proposed maglev vehicle successfully completed testing, the test track was to be extended in each direction to Tokyo and Osaka and opened to the public as a revenue-generating service. This new commercial line was expected to relieve passenger demand on the Shinkansen high-speed trains, which currently operate at peak speeds of 300 km/h (186 mph).
In the United States, two high-speed maglev projects using Transrapid technology have been selected by the U.S. Department of Transportation for environmental and preconstruction planning. One is a proposed 76-km (47-mi) track linking the city of Pittsburgh, Pennsylvania, its eastern suburbs, and Pittsburgh Airport. The other project is a proposed 64-km (40-mi) track linking Camden Yards in Baltimore, Maryland, the Baltimore-Washington Airport, and Union Station in Washington, D.C. For maglev systems to become a significant part of the U.S. transportation system, they will have to be viewed as an essential part of an integrated transportation infrastructure.