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The overhead wiring, generally having two separate overhead lines and the rail for the third phase, was more complicated, and the low frequency used required a separate generation or conversion and distribution system. Train speed was restricted to one to four speeds, with two or four speeds obtained by pole-changing or cascade operation or both.
SNCF Class B 81500, an example of an electro-diesel multiple unit. An electro-diesel multiple unit (EDMU) or bi-mode multiple unit (BMU) is a form of a multiple unit train that can be powered either by electric power picked up from the overhead lines or third rail (like an electric multiple unit – EMU) or by using an onboard diesel engine, driving an electric generator, which produces ...
[citation needed] The additional rail carries the electrical return that, on third-rail and overhead networks, is provided by the running rails. On the London Underground, a top-contact third rail is beside the track, energized at +420 V DC , and a top-contact fourth rail is located centrally between the running rails at −210 V DC , which ...
Either two three-phase units or three single-phase units can be used. With the latter variant only one type of transformer is used, making the supply of a spare transformer more economical. Converter transformers operate with high flux Power Steps In the Four Steps of the Converter per cycle, and so produce more acoustic noise than normal three ...
The New Haven chose the 11 kV 25 Hz system, later used by the PRR, in addition to working with Westinghouse to develop AC/DC electric motors (locomotives) to run on both AC overhead lines and DC third rail. The main line, now Metro-North Railroad's New Haven Line, was converted to 12.5 kV 60 Hz in 1985.
Since 1940. Used both third rail DC (1200 V) and overhead line AC (6.3 kV 25 Hz) until 1955. Also uses German standard 15 kV AC 16 2/3 Hz overhead electrification on the section between Neugraben and Stade on line S3, opened in December 2007.
Most overhead supply systems are either DC or single phase AC, using a single wire with return through the grounded running rails. Three phase AC systems use a pair of overhead wires, and paired trolley poles. Electric overhead cranes and gantry cranes may use a current collector system to provide power over the full length of their operating ...
In this system, the current is mainly carried between the overhead line and a feeder transmission line instead of the rail. The overhead line (3) and feeder (5) are on opposite phases so the voltage between them is 50 kV, while the voltage between the overhead line (3) and the running rails (4) remains at 25 kV. Periodic autotransformers (9 ...