![CR400BF-G-5168@IFP (20210128114409)](https://upload.wikimedia.org/wikipedia/commons/7/73/CR400BF-G-5168%40IFP_%2820210128114409%29.jpg)
An electric multiple unit or EMU is a
multiple-unit
A multiple-unit train or simply multiple unit (MU) is a self-propelled train composed of one or more carriages joined together, which when coupled to another multiple unit can be controlled by a single driver, with multiple-unit train contr ...
train
In rail transport, a train (from Old French , from Latin , "to pull, to draw") is a series of connected vehicles that run along a railway track and Passenger train, transport people or Rail freight transport, freight. Trains are typically pul ...
consisting of self-propelled carriages using
electricity
Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described ...
as the motive power. An EMU requires no separate
locomotive
A locomotive or engine is a rail transport vehicle that provides the Power (physics), motive power for a train. If a locomotive is capable of carrying a payload, it is usually rather referred to as a multiple unit, Motor coach (rail), motor ...
, as electric
traction motor
A traction motor is an electric motor used for propulsion of a vehicle, such as locomotives, electric vehicle, electric or hydrogen vehicles, elevators or electric multiple unit.
Traction motors are used in electrically powered rail vehicles (ele ...
s are incorporated within one or a number of the carriages. An EMU is usually formed of two or more semi-permanently coupled carriages, but electrically powered single-unit
railcar
A railcar (not to be confused with a railway car) is a self-propelled railway vehicle designed to transport passengers. The term "railcar" is usually used in reference to a train consisting of a single coach (carriage, car), with a drive ...
s are also generally classed as EMUs. The great majority of EMUs are passenger trains, but versions also exist for carrying mail.
EMUs are popular on commuter and suburban rail networks around the world due to their fast acceleration and pollution-free operation. Being quieter than
diesel multiple unit
A diesel multiple unit or DMU is a multiple-unit train powered by on-board diesel engines. A DMU requires no separate locomotive, as the engines are incorporated into one or more of the carriages. Diesel-powered single-unit railcars are also ...
s (DMUs) and
locomotive
A locomotive or engine is a rail transport vehicle that provides the Power (physics), motive power for a train. If a locomotive is capable of carrying a payload, it is usually rather referred to as a multiple unit, Motor coach (rail), motor ...
-hauled trains, EMUs can operate later at night and more frequently without disturbing nearby residents. In addition, tunnel design for EMU trains is simpler as no provision is needed for exhausting fumes, although retrofitting existing limited-clearance tunnels to accommodate the extra equipment needed to transmit electric power to the train can be difficult.
History
Multiple unit train control was first used in the 1890s.
The
Liverpool Overhead Railway
The Liverpool Overhead Railway (known locally as the Dockers' Umbrella or Ovee) was an overhead railway in Liverpool which operated along the Liverpool Docks and opened in 1893 with lightweight electric multiple units. The railway had a number ...
opened in 1893 with two-car electric multiple units, controllers in cabs at both ends directly controlling the traction current to motors on both cars.
The multiple unit traction control system was developed by
Frank Sprague
Frank Julian Sprague (July 25, 1857 in Milford, Connecticut – October 25, 1934) was an American inventor who contributed to the development of the electric motor, electric railways, and electric elevators. His contributions were especially i ...
and first applied and tested on the
South Side Elevated Railroad (now part of the
Chicago 'L'
(''City in a Garden''); I Will
, image_map =
, map_caption = Interactive Map of Chicago
, coordinates =
, coordinates_footnotes =
, subdivision_type = Country
, subdivision_name ...
) in 1897. In 1895, derived from his company's invention and production of direct current elevator control systems, Frank Sprague invented a multiple unit controller for electric train operation. This accelerated the construction of electric traction railways and trolley systems worldwide. Each car of the train has its own traction motors: by means of motor control relays in each car energized by train-line wires from the front car all of the traction motors in the train are controlled in unison.
Types
![MNCRR M-8 at NEC Port Chester](https://upload.wikimedia.org/wikipedia/commons/f/f7/MNCRR_M-8_at_NEC_Port_Chester.jpg)
The cars that form a complete EMU set can usually be separated by function into four types: power car, motor car, driving car, and trailer car. Each car can have more than one function, such as a motor-driving car or power-driving car.
* A power car carries the necessary equipment to draw power from the
electrified infrastructure, such as
pickup shoes for
third rail systems and
pantographs
A pantograph (, from their original use for copying writing) is a mechanical linkage connected in a manner based on parallelograms so that the movement of one pen, in tracing an image, produces identical movements in a second pen. If a line dr ...
for
overhead systems, and
transformer
A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer' ...
s.
* Motor cars carry the
traction motor
A traction motor is an electric motor used for propulsion of a vehicle, such as locomotives, electric vehicle, electric or hydrogen vehicles, elevators or electric multiple unit.
Traction motors are used in electrically powered rail vehicles (ele ...
s to move the train, and are often combined with the power car to avoid high-voltage inter-car connections.
* Driving cars are similar to a
cab car, containing a driver's cab for controlling the train. An EMU will usually have two driving cars at its outer ends.
* Trailer cars are any cars (sometimes semi-permanently coupled) that carry little or no traction or power related equipment, and are similar to
passenger car
A car or automobile is a motor vehicle with wheels. Most definitions of ''cars'' say that they run primarily on roads, seat one to eight people, have four wheels, and mainly transport people instead of goods.
The year 1886 is regarded as ...
s in a locomotive-hauled train.
On third rail systems, the outer vehicles usually carry the pick up shoes with the motor vehicles receiving the current via
intra-unit connections.
Many modern two-car EMU sets are set up as
twin
Twins are two offspring produced by the same pregnancy.MedicineNet > Definition of TwinLast Editorial Review: 19 June 2000 Twins can be either ''monozygotic'' ('identical'), meaning that they develop from one zygote, which splits and forms two em ...
or "married pair" units. While both units in a married pair are typically driving motors, the ancillary equipment (air compressor and tanks, batteries and charging equipment, traction power and control equipment, etc.) are shared between the two cars in the set. Since neither car can operate without its "partner", such sets are permanently coupled and can only be split at maintenance facilities. Advantages of married pair units include weight and cost savings over single-unit cars (due to halving the ancillary equipment required per set) while allowing all cars to be powered, unlike a motor-trailer combination. Each car has only one control cab, located at the outer end of the pair, saving space and expense over a cab at both ends of each car. Disadvantages include a loss of operational flexibility, as trains must be multiples of two cars, and a failure on a single car could force removing both it and its partner from service.
As high speed trains
Some of the more famous electric multiple units in the world are high-speed trains: the Italian
Pendolino and
Frecciarossa 1000
The Frecciarossa 1000, is a high-speed train operated by Italian state railway operator Trenitalia. It was co-developed as a joint venture between Italian rail manufacturer Hitachi Rail Italy (initially AnsaldoBreda) and multinational conglomerat ...
,
Shinkansen in Japan, the
China Railway High-speed
China Railway High-speed (CRH) is a high-speed rail service operated by China Railway.
The introduction of CRH series was a major part of the sixth national railway speedup, implemented on April 18, 2007. By the end of 2020, China Railway H ...
in China,
ICE 3 in Germany, and the British Rail
class 395 Javelin. The retired New York–Washington ''
Metroliner'' service, first operated by the
Pennsylvania Railroad
The Pennsylvania Railroad (reporting mark PRR), legal name The Pennsylvania Railroad Company also known as the "Pennsy", was an American Class I railroad that was established in 1846 and headquartered in Philadelphia, Pennsylvania. It was named ...
and later by
Amtrak
The National Railroad Passenger Corporation, Trade name, doing business as Amtrak () , is the national Passenger train, passenger railroad company of the United States. It operates inter-city rail service in 46 of the 48 contiguous United Stat ...
, also featured high-speed electric multiple-unit cars, known as the
Budd Metroliner
The Budd Metroliner was a class of American electric multiple unit (EMU) railcar designed for first-class, high-speed service between New York City and Washington, D.C. on the Northeast Corridor. They were designed for operation up to : what w ...
.
Fuel cell development
EMUs powered by
fuel cell
A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen) and an oxidizing agent (often oxygen) into electricity through a pair of redox reactions. Fuel cells are different from most batteries in requ ...
s are under development. If successful, this would avoid the need for an
overhead line
An overhead line or overhead wire is an electrical cable that is used to transmit electrical energy to electric locomotives, trolleybuses or trams. It is known variously as:
* Overhead catenary
* Overhead contact system (OCS)
* Overhead equipmen ...
or
third rail
A third rail, also known as a live rail, electric rail or conductor rail, is a method of providing electric power to a railway locomotive or train, through a semi-continuous rigid conductor placed alongside or between the rails of a railway t ...
. An example is
Alstom
Alstom SA is a French multinational rolling stock manufacturer operating worldwide in rail transport markets, active in the fields of passenger transportation, signalling, and locomotives, with products including the AGV, TGV, Eurostar, Avelia ...
’s
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
-powered
Coradia iLint
The Alstom Coradia LINT is an articulated railcar manufactured by Alstom since 1999, offered in diesel and hydrogen fuel models.
The acronym ''LINT'' is short for the German ''"leichter innovativer Nahverkehrstriebwagen"'' (light innovative loca ...
. The term
hydrail has been coined for hydrogen-powered rail vehicles.
Battery electric multiple unit
Many
battery electric multiple units
Battery most often refers to:
* Electric battery, a device that provides electrical power
* Battery (crime), a crime involving unlawful physical contact
Battery may also refer to:
Energy source
*Automotive battery, a device to provide power t ...
are in operation around the world, with the take up being strong. Many are bi-modal taking energy from onboard battery banks and line pickups such as overhead wires or third rail. In most cases the batteries are charged via the electric pickup when operating on electric mode.
Comparison with locomotives
EMUs, when compared with
electric locomotive
An electric locomotive is a locomotive powered by electricity from overhead lines, a third rail or on-board energy storage such as a battery or a supercapacitor. Locomotives with on-board fuelled prime movers, such as diesel engines or gas ...
s, offer:
*Higher acceleration, since there are more motors sharing the same load, more motors allows for a higher total motor power output
*Braking, including
Eddy current,
rheostatic and/or
regenerative braking on multiple axles at once, greatly reducing wear on brake parts (as the wear can be distributed among more brakes) and allowing for faster braking (lower/reduced braking distances)
*Reduced axle loads, since the need for a heavy locomotive is eliminated; this in turn allows for simpler and cheaper structures that use less material (like bridges and viaducts) and lower structure maintenance costs
*Reduced ground vibrations, due to the above
*Lower adhesion coefficients for driving (powered) axles, due to lower weight on these axles; weight is not concentrated on a locomotive
*A higher degree of redundancy - performance is only minimally affected following the failure of a single motor or brake
*Higher seating capacity, since there is no locomotive; all cars can contain seats.
Electric locomotives, when compared to EMUs, offer:
*Less electrical equipment per train resulting in lower train manufacturing and maintenance costs
*Easily allows for lower noise and vibration in passenger cars, since there are no motors or gearboxes on the bogies below the cars
Gallery
File:Local-train-at-howrah-jn.jpg, EMU train in India.
File:NewGeneration710.jpg, A New Generation Rollingstock train in the Queensland Rail City network, Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
File:ICE 3 Oberhaider-Wald-Tunnel.jpg, A Deutsche Bahn
The (; abbreviated as DB or DB AG) is the national railway company of Germany. Headquartered in the Bahntower in Berlin, it is a joint-stock company ( AG). The Federal Republic of Germany is its single shareholder.
describes itself as the se ...
ICE 3 EMU capable of up to in Rhineland-Palatinate
Rhineland-Palatinate ( , ; german: link=no, Rheinland-Pfalz ; lb, Rheinland-Pfalz ; pfl, Rhoilond-Palz) is a western state of Germany. It covers and has about 4.05 million residents. It is the ninth largest and sixth most populous of the ...
, Germany
Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...
File:SOB RABe 526 107 (51537387480).jpg, Stadler FLIRT-III EMU "Traverso" of Südostbahn
The Südostbahn (German, literally meaning "South-Eastern Railway") – commonly abbreviated to SOB – is a Swiss adhesion railway company, and a network in Central and Eastern Switzerland. It resulted from the merger of the original SOB wit ...
operating as ''Voralpen-Express
The ''Voralpen-Express'' (''VAE'') is a named train connecting small to medium-sized cities and villages in Central and Eastern Switzerland, carrying this name since 1992. It is operated by Südostbahn (SOB) and runs every hour between St. Galle ...
'' in Switzerland
). Swiss law does not designate a ''capital'' as such, but the federal parliament and government are installed in Bern, while other federal institutions, such as the federal courts, are in other cities (Bellinzona, Lausanne, Luzern, Neuchâtel ...
File:South Side Elevated Railroad car 1.jpg, South Side Elevated Railroad car #1, one of the cars that Frank Sprague converted to MU operation in Chicago
File:Lodi - stazione ferroviaria - Treno Servizio Regionale - linea S1.jpg, An Italian TSR double-decker EMU
File:ČD Class 641 in Adamov.JPG, A RegioPanter electric train
File:Pendolino - ČD Class 680 (2).jpg, ČD Class 680
ČD Class 680 are EMUs operating in the Czech Republic, using tilting Pendolino technology intended for the SuperCity train service. Built by Alstom (originally Fiat Ferroviaria), they were largely based on the nine-car ETR 470. While testin ...
File:483008 at Smallbrook Junction in 2020.jpg, A British Rail Class 483 at Smallbrook Junction
Smallbrook Junction railway station is a railway station on the Isle of Wight, England. It is unusual because it has no public access but exists purely to provide a connection between two rail systems.
Another similar station is Manulla Junction ...
on the Isle of Wight
The Isle of Wight ( ) is a county in the English Channel, off the coast of Hampshire, from which it is separated by the Solent. It is the largest and second-most populous island of England. Referred to as 'The Island' by residents, the Isle of ...
. An example of converted 1938 tube stock
The London Underground 1938 Stock was a London Underground tube stock design. A total of 1,121 cars were built by Metro-Cammell and Birmingham RC&W. An additional 173 cars were added to the fleet by the end of 1953, comprising 91 new bui ...
, these trains were the oldest electrical multiple units in mainline operation in the United Kingdom, being 82 years old at the time of their retirement in 2021.
File:Vande Bharat express for Katra IMG 20200131 054006.jpg, An Indian Railways
Indian Railways (IR) is a statutory body under the ownership of Ministry of Railways, Government of India that operates India's national railway system. It manages the fourth largest national railway system in the world by size, with a tot ...
Vande Bharat Express train capable of up to 180 km/h (112 mph)
File:ZSSK 671.001.jpg, ZSSK Class 671
File:Mumbai Train.JPG, Mumbai suburban rail
File:Syonan-Shinjuku Line E233-3000 Series 20190924.jpg, An E233 series EMU on the Shōnan–Shinjuku Line in September 2019
File:Ligne de Nanterre a Sartrouville - Viaduc de Nanterre - MI09 - Avril 2012 (4) cropped.jpg, MI 09 on RER A Line in November 2012
File:KTM Class 93 Pulau Sebang 015347.jpg, KTM Class 93
The Class 93 is a type of electric multiple unit used by Keretapi Tanah Melayu for its intercity Electric Train Service (ETS). A total of 10 sets in 6-car formations have been built and delivered by CRRC Zhuzhou (initially CSR Zhuzhou) of China, ...
of KTM ETS arriving Pulau Sebang
File:Скоростной_поезд_"Хендай".jpg, HRCS2
The HRCS2 Hyundai Rotem is a dual-voltage electric multiple unit built by Hyundai Rotem for the Ukrainian Railways.
History
The trains were ordered by Ukrainian Railways in preparation for the football championship UEFA Euro 2012 to transpor ...
of the Ukrainian Railways
See also
*
Electro-diesel multiple unit
An electro-diesel multiple unit (EDMU) or bi-mode multiple unit (BMU) is a form of a multiple unit 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 usi ...
*
Diesel multiple unit
A diesel multiple unit or DMU is a multiple-unit train powered by on-board diesel engines. A DMU requires no separate locomotive, as the engines are incorporated into one or more of the carriages. Diesel-powered single-unit railcars are also ...
*
Battery electric multiple unit
*
British electric multiple units
An electric multiple unit (EMU) is an electric train capable of operating in multiple with other EMUs that does not have a separate locomotive, typically passenger trains with accommodation in every vehicle and a driving position at each end. Th ...
References
{{DEFAULTSORT:Electric Multiple Unit
Multiple units
Electric rail transport