Electric multiple unit

An electric multiple unit or EMU is a multiple unit train consisting of self-propelled carriages, using electricity as the motive power. An EMU requires no separate locomotive, as electric traction motors are incorporated within one or a number of the carriages. Most EMUs are used for passenger trains, but some have been built or converted for specialised non-passenger roles, such as carrying mail or luggage, or in departmental use, for example as de-icing trains. An EMU is usually formed of two or more semi-permanently coupled carriages, but electrically powered single-unit railcars are also generally classed as EMUs.

EMUs are popular on commuter and suburban rail networks around the world due to their fast acceleration and pollution-free operation. Being quieter than DMUs and locomotive-drawn trains, EMUs can operate later at night and more frequently without disturbing residents living near the railway lines. In addition, tunnel design for EMU trains is simpler as provisions do not need to be made for diesel exhaust fumes, although retrofitting existing tunnels to accommodate the extra equipment needed to transmit the power to the train can be expensive and difficult if the tunnel has limited clearance.

Electric multiple unit (Queensland Rail)

The Electric Multiple Units are a class of electric multiple units manufactured by Walkers Limited, Maryborough for Queensland Rail between 1979 and 1986. They were the first EMUs in Queensland and remain in service with Citytrain.

All units feature air-conditioning, power operated automatic doors, fabric covered padded seating, emergency intercoms and a public address system.

History

In 1977 Walkers Limited, Maryborough were awarded a contract to build 13 EMUs with electrical equipment to be supplied by ASEA. These were the first EMUs in Queensland, entering revenue service when the first part of the Brisbane rail network was electrified between Ferny Grove and Darra in November 1979. Further orders saw the fleet total with the last delivered in December 1987.

Current Operation

EMUs still constitute close to half of the Citytrain fleet and are in regular and frequent usage. They operate on all Citytrain suburban lines in either three or six carriage sets. EMU01-EMU04, EMU06-EMU59 and EMU80-EMU88 have driving cabs at both ends and can either operate as three or six car sets. EMU60-EMU79 have only a single driving cab, and as a result, they can operate only as part of a six car set. EMU05 was extensively damaged in 2001 and is no longer in service.

Multiple unit

Multiple units (MU) are self-propelled train carriages capable of coupling with other units of the same or similar type and still being controlled from one driving cab. Often these are passenger trainsets consisting of more than one carriage. Single self-propelling carriages (also called railcars, rail motor coaches or railbuses) are multiple units if capable of operating with other units.

Multiple units are classified by their power source and are of two main types: electric multiple unit (EMU) or diesel multiple unit (DMU). Diesel-powered units may be further classified by their transmission type: diesel-electric (DEMU), diesel-mechanical (DMMU) or diesel-hydraulic (DHMU).

Locomotives utilising multiple-unit train control are not multiple units.

History

Multiple-unit train control was first used in Electric Multiple Units in the 1890s. This allowed electrically-powered rapid transit trains to be operated from a single driving position. Early users of such multiple units include the Liverpool Overhead Railway (the first multiple units) and Chicago's South Side Elevated Railroad (the first units to use a low-voltage control system).