British electric multiple units
British self-powered electric trains / From Wikipedia, the free encyclopedia
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An electric multiple unit (EMU) is an electric self-powered train, capable of operating in multiple with other EMUs and without the need for a locomotive; these are typically passenger trains with accommodation in every vehicle and a driving position at each end. The term can also be used to describe a train that is a permanent formation with a non-driving power car, such as the Advanced Passenger Train.[note 1] As of December 2010[update], two-thirds of the passenger carriages in Great Britain are formed in EMUs.
Electric railways began in Great Britain in 1883 and the first EMU ran on the Liverpool Overhead Railway in 1893. In the early 20th century, systems were developed where all the motors on a train could be controlled by a low voltage signal from any cab. Due to problems using steam locomotives underground, the underground railways in London and Liverpool were early adopters of 600 V DC electric traction and, by 1907, underground railways in London and some provincial cities were running electric trains. A 6.7 kV 25 Hz overhead system was also used from 1908. After the railway companies were grouped in 1923, the Southern Railway greatly expanded the third rail DC electrification, replacing some early AC electrification. Overhead lines at 1500 V DC were planned and installed just before and after the Second World War. The early EMU carriages, similar to contemporaneous locomotive-hauled carriages, were constructed of wood with hinged doors with accommodation in saloons or compartments. As time went on, more steel became used in carriage construction.
After the Second World War, the railways were nationalised and the 25 kV 50 Hz overhead system was installed; this eventually replaced all 1500 V DC systems. South of London, the Southern Railway third rail electrification system continued to expand.