Maglevs

A major problem is the design of a propulsion system for a vehicle that has no contact with a guideway. The only reasonable choice is a linear motor that uses magnetic fields to propel the vehicle. The development of a linear motor and its control system is at least as formidable a challenge as the development of a maglev suspension system. 

There are four competing maglev technologies electromagnetic suspension, electrodynamic suspension, linear synchronous motor, and linear induction motor. 

EMS requires about 1 to 2 kW of magnet power for evei y ton of vehicle mass. At modest and high speeds this power loss is small compared with the power loss due to aerodynamic drag. EMS is the favored approach for urban maglev and is suitable for high speeds if the use of a minimal 10 mm air gap is acceptable. 

The principal disadvantage of the short stator design is the need to transfer power to the vehicle. If this is done with sliding contacts, as with conventional electric trains, then some of the advantages of maglev are lost. If it is done via inductive transfer, then the guideway cost is increased. 

A low speed EMS maglev system was constructed in Birmingham in 1984. This design had an air gap of 10 mm and used short stator LIM propulsion with power delivered to the vehicle via sliding contacts and a third rail. It provided transportation between an airport and a train station and worked nearly flawlessly for more than twelve years. When problems did develop there was no one with interest and ability to repair it, so it was removed. 

The best and most up-to-date references are Internet websites. Most of these can be reached via links from the U.S. Department of Transportation site . This site has links to the Federal Railroad Administration and the Federal Transit Administration, each of which has links to other national and international maglev sites. Additional maglev sites can be reached from the Innovative Transportation Technologies site . More details on EMS, LSM, and LIM can be found on the German Transrapid and Japanese HSST sites. More details on EDS and LSM can be found on the Japanese Railroad Technical Research Institute (RTRI) site. 

Less noisy. Maglev vehicles are quiet. Transrapid test data shows 5 to 10 dB less noise than for a tram at the same speed or the same noise for speeds that are 100 km/h (62 mph) higher. Some newer maglev designs with more streamlining have even lower noise. 

Safer. The system can be as safe or safer than any other system. If it is well designed with dedicated nglits of way, a Ingli level of automation and no pliys-ical contact, then the most common cause of accidents will have been eliminated. There have been no significant accidents in all of the maglev tests that have been run. If maglev attracts people away from other modes it could save many lives. 

Faster. The system can be designed to operate safely at very high speeds. But speed is relative so that 161 km/li (100 mph) operation in an urban area will be dramatically faster than alternatives. Some people believe that maglev designers have put too much emphasis on speed and this has made the designs expensive. 

Yamanashi MAGLEV Test Line, 23 865 Yankee dryer, 18 122, 129 Yard wastes... 

FIGURE 21.15 An experimental magnetically levitated train (Maglev) in Japan is suspended above superconducting magnets that are cooled with liquid helium. This five-car train has attained a speed of 552 km/h in a manned vehicle run. 

Brown, Alan S. Maglev Goes To Work. Mechanical Engineering Web site. Available online. URL http //www.memagazine.org/ june06/features/maglev/maglev.html. 

Yet, recently there has been a renewed interest in rail alternatives—high-speed ones, of course, in keeping with the national preference. More specifically, the focus has centered on fast trains that would take advantage of developments in superconductivity and give us one of the most spectacular of all of its potential applications magnetically levitated trains, maglevs, that would literally fly between... 

The Japanese alternative is the maglev system, and several prototype trains have been tested successfully by the country s engineers. What is maglev, however, and how does it work And how will the new superconducting materials contribute to giving us a transportation system that would be a realistic version of the fabled flying carpet ... 

Fascinating it was, but few people paid attention—except for the Japanese. They had read Powell and Danby s paper with the same keen interest with which years later, they would read the obscure journal detailing the discovery by IBM scientists of a ceramic compound superconducting at a record-high Kelvin. In 1970, they exhibited a model of the train at the Osaka World s Fair. By 1979, they tested another at speeds that hit a top of 321 miles per hour, a world record. In 1985, another maglev carried more than a half-million passengers on short runs at the science fair at Tsukuba. 

The Japanese maglev system with its superconducting magnets relies heavily on the Brookhaven and Bitter Labs concept and on the fact that like magnetic poles repel one another. 

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