Definition
Magnetic levitation transport, or maglev, is a form of transportation that suspends, guides and propels vehicles (especially trains) using electromagnetic force.
Basics
See also Magnetic Levitation
The maglev method can be faster than wheeled mass transit systems, potentially reaching velocities comparable to turboprop and jet aircraft (900 km/h, 600 mph). The highest recorded speed of a maglev train is 581 km/h (361 mph), achieved in Japan in 2003, which is 4 mph more than the conventional TGV speed record.
The highest recorded speed of a Maglev train is 581 kilometres per hour (361 mph), achieved in Japan in 2003, 6 kilometres per hour (3.7 mph) faster than the conventional TGV speed record.
The first commercial Maglev "people-mover" was officially opened in 1984 in Birmingham, England. It operated on an elevated 600-metre (2,000 ft) section of monorail track between Birmingham International Airport and Birmingham International railway station, running at speeds up to 42 km/h (26 mph); the system was eventually closed in 1995 due to reliability and design problems.
Perhaps the most well known implementation of high-speed maglev technology currently operating commercially is the IOS (initial operating segment) demonstration line of the German-built Transrapid train in Shanghai, China that transports people 30 km (18.6 miles) to the airport in just 7 minutes 20 seconds, achieving a top speed of 431 km/h (268 mph), averaging 250 km/h (160 mph).
Commercial operation
The first commercial Maglev was opened in 1984 in Birmingham, England, covering some 600 meters between its airport and railhub, but was eventually closed in 1995 due to reliability and design problems. It operated at 42 km/h (26 mph). A contractor added an extra layer of fiberglass, and new trains had to be built. Its speedometer was based on radar, and was thrown off by snow.
The best-known high-speed maglev currently operating commercially is the IOS (initial operating segment) demonstration line of the German built Transrapid train in Shanghai, China that transports people 30 km (18.6 miles) to the airport in just 7 minutes 20 seconds, achieving a top velocity of 431 km/h (268 mph), averaging 250 km/h (150 mph).
Other commercially operating lines exist in Japan, such as the Linimo line. Other maglev projects worldwide are being studied for feasibility. In Japan at the Yamanashi test track, current maglev train technology is mature, but costs and problems remain a barrier to development, alternate technologies are being developed to address those issues.
Technology
All operational implementations of maglev technology have had minimal overlap with wheeled train technology and have not been compatible with conventional rail tracks. Because they cannot share existing infrastructure, maglevs must be designed as complete transportation systems. The term "maglev" refers not only to the vehicles, but to the railway system as well, specifically designed for magnetic levitation and propulsion.
There are two primary types of maglev technology:
- electromagnetic suspension (EMS) uses the attractive magnetic force of a magnet beneath a rail to lift the train up.
- electrodynamic suspension (EDS) uses a repulsive force between two magnetic fields to push the train away from the rail.
Another experimental technology, which was designed, proven mathematically, peer reviewed, and patented, but is yet to be built, is the magnetodynamic suspension (MDS), which uses the attractive magnetic force of a permanent magnet array near a steel track to lift the train and hold it in place.
Advantages and disadvantages
Compared to conventional trains
Major comparative differences between the two technologies lie in backward-compatibility, rolling resistance, weight, noise, design constraints, and control systems.
Backwards Compatibility Maglev trains currently in operation are not compatible with conventional track, and therefore require all new infrastructure for their entire route. By contrast conventional high speed trains such as the TGV are able to run at reduced speeds on existing rail infrastructure, thus reducing expenditure where new infrastructure would be particularly expensive (such as the final approaches to city terminals), or on extensions where traffic does not justify new infrastructure.
Efficiency Due to the lack of physical contact between the track and the vehicle, maglev trains experience no rolling resistance, leaving only air resistance and electromagnetic drag, potentially improving power efficiency.
Weight The weight of the large electromagnets in many EMS and EDS designs is a major design issue. A very strong magnetic field is required to levitate a massive train. For this reason one research path is using superconductors to improve the efficiency of the electromagnets, and the energy cost of maintaining the field.
Noise. Because the major source of noise of a maglev train comes from displaced air, maglev trains produce less noise than a conventional train at equivalent speeds. However, the psychoacoustic profile of the maglev may reduce this benefit: A study concluded that maglev noise should be rated like road traffic while conventional trains have a 5-10 dB "bonus" as they are found less annoying at the same loudness level.
Design Comparisons Braking and overhead wire wear have caused problems for the Fastech 360 railed Shinkansen. Maglev would eliminate these issues. Magnet reliability at higher temperatures is a countervailing comparative disadvantage, but new alloys and manufacturing techniques have resulted in magnets that maintain their levitational force at higher temperatures.
As with many technologies, advances in linear motor design have addressed the limitations noted in early maglev systems. As linear motors must fit within or straddle their track over the full length of the train, track design for some EDS and EMS maglev systems is challenging for anything other than point-to-point services. Curves must be gentle, while switches are very long and need care to avoid breaks in current. An SPM maglev system, in which the vehicle permanently levitated over the tracks, can instantaneously switch tracks using electronic controls, with no moving parts in the track. A prototype SPM maglev train has also navigated curves with radius equal to the length of the train itself, which indciates that a full-scale train should be able to navigate curves with the same or narrower radius as a conventional train.
Control Systems EMS Maglev needs very fast-responding control systems to maintain a stable height above the track; this needs careful design in the event of a failure in order to avoid crashing into the track during a power fluctuation. Other maglev systems do not necessarily have this problem. For example, SPM maglev systems have a stable levitation gap of several centimeters.
Compared to aircraft
For many systems, it is possible to define a lift-to-drag ratio. For maglev systems these ratios can exceed that of aircraft (for example Inductrack can approach 200:1 at high speed, far higher than any aircraft). This can make maglev more efficient per kilometre. However, at high cruising speeds, aerodynamic drag is much larger than lift-induced drag. Jet transport aircraft take advantage of low air density at high altitudes to significantly reduce drag during cruise, hence despite their lift-to-drag ratio disadvantage, they can travel more efficiently at high speeds than maglev trains that operate at sea level (this has been proposed to be fixed by the vactrain concept). Aircraft are also more flexible and can service more destinations with provision of suitable airport facilities.
Unlike airplanes, maglev trains are powered by electricity and thus need not carry fuel. Aircraft fuel is a significant danger during takeoff and landing accidents. Also, electric trains emit little carbon dioxide emissions, especially when powered by nuclear or renewable sources.
History of maximum speed record by a trial run
- 1971 - West Germany - Prinzipfahrzeug - 90 km/h
- 1971 - West Germany -TR-02(TSST)- 164 km/h
- 1972 - Japan - ML100 – 60 km/h - (manned)
- 1973 - West Germany - TR04 - 250 km/h (manned)
- 1974 - West Germany - EET-01 - 230 km/h (unmanned)
- 1975 - West Germany - Komet - 401.3 km/h (by steam rocket propulsion, unmanned)
- 1978 - Japan - HSST-01 - 307.8 km/h (by supporting rockets propulsion, made in Nissan, unmanned)
- 1978 - Japan - HSST-02 - 110 km/h (manned)
- 1979-12-12 - Japan-ML-500R - 504 km/h (unmanned) It succeeds in operation over 500 km/h for the first time in the world.
- 1979-12-21 - Japan -ML-500R- 517 km/h (unmanned)
- 1987 - West Germany - TR-06 - 406 km/h (manned)
- 1987 - Japan - MLU001 - 400.8 km/h (manned)
- 1988 - West Germany - TR-06 - 412.6 km/h (manned)
- 1989 - West Germany - TR-07 - 436 km/h (manned)
- 1993 - Germany - TR-07 - 450 km/h (manned)
- 1994 - Japan - MLU002N - 431 km/h (unmanned)
- 1997 - Japan - MLX01 - 531 km/h (manned)
- 1997 - Japan - MLX01 - 550 km/h (unmanned)
- 1999 - Japan - MLX01 - 548 km/h (unmanned)
- 1999 - Japan - MLX01 - 552 km/h (manned/five formation). Guinness authorization.
- 2003 - China - Transrapid SMT (build in Germany) - 501.5 km/h (manned/three formation)
- 2003 - Japan - MLX01 - 581 km/h (manned/three formation). Guinness authorization.
Source: Wikipedia (All text is available under the terms of the GNU Free Documentation License and Creative Commons Attribution-ShareAlike License.)
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