Maglev

Maglev (derived from magnetic levitation) is a system of rail transport whose rolling stock is levitated by electromagnets rather than rolled on wheels, eliminating rolling resistance.

Compared to conventional railways, maglev trains have higher top speeds, superior acceleration and deceleration, lower maintenance costs, improved gradient handling, and lower noise. However, they are more expensive to build, cannot use existing infrastructure, and use more energy at high speeds.

Maglev trains have set several speed records. The train speed record of 603 km/h (375 mph) was set by the experimental Japanese L0 Series maglev in 2015. From 2002 until 2021, the record for the highest operational speed of a passenger train of 431 kilometres per hour (268 mph) was held by the Shanghai maglev train, which uses German Transrapid technology. The service connects Shanghai Pudong International Airport and the outskirts of central Pudong, Shanghai. At its historical top speed, it covered the distance of 30.5 kilometres (19 mi) in just over 8 minutes (average speed: 228.75 km/h).

Different maglev systems achieve levitation in different ways, which broadly fall into two categories: electromagnetic suspension (EMS) and electrodynamic suspension (EDS). Propulsion is typically provided by a linear motor. The power needed for levitation is typically not a large percentage of the overall energy consumption of a high-speed maglev system. Instead, overcoming drag takes the most energy. Vactrain technology has been proposed as a means to overcome this limitation.

Despite over a century of research and development, there are only seven operational maglev trains today — four in China, two in South Korea, and one in Japan.

Two inter-city maglev lines are currently under construction, the Chūō Shinkansen connecting Tokyo and Nagoya (with further connection to Osaka) and a line between Changsha and Liuyang in Hunan Province, China.

In the late 1940s, the British electrical engineer Eric Laithwaite, a professor at Manchester University, developed the first full-size working model of the linear induction motor. He became professor of heavy electrical engineering at Imperial College London in 1964, where he continued his successful development of the linear motor. Since linear motors do not require physical contact between the vehicle and guideway, they became a common fixture on advanced transportation systems in the 1960s and 1970s. Laithwaite joined one such project, the Tracked Hovercraft RTV-31, based near Cambridge, UK, although the project was cancelled in 1973.

The linear motor was naturally suited to use with maglev systems as well. In the early 1970s, Laithwaite discovered a new arrangement of magnets, the magnetic river, that allowed a single linear motor to produce both lift and forward thrust, allowing a maglev system to be built with a single set of magnets. Working at the British Rail Research Division in Derby, along with teams at several civil engineering firms, the "transverse-flux" system was developed into a working system.^{[citation needed]}