![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 transport people or freight. Trains are typically pulled or pushed by locomotives (often ...
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 describ ...
as the motive power. An EMU requires no separate
locomotive, as electric
traction motor
A traction motor is an electric motor used for propulsion of a vehicle, such as locomotives, electric or hydrogen vehicles, elevators or electric multiple unit.
Traction motors are used in electrically powered rail vehicles ( electric multiple ...
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 dri ...
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 units (DMUs) and
locomotive-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
The South Side Elevated Railroad (originally Chicago and South Side Rapid Transit Railroad) was the first elevated rapid transit line in Chicago, Illinois. The line ran from downtown Chicago to Jackson Park, with branches to Englewood, Normal Pa ...
(now part of the
Chicago 'L') 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 shoe
Electric current collectors are used by trolleybuses, trams, electric locomotives or EMUs to carry electrical power from overhead lines, electrical third rails, or ground-level power supplies to the electrical equipment of the vehicles. Those for ...
s for
third rail systems and
pantographs 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 or hydrogen vehicles, elevators or electric multiple unit.
Traction motors are used in electrically powered rail vehicles ( electric multiple ...
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
A control car, cab car (North America), control trailer, or driving trailer (UK and Ireland) is a non-powered rail vehicle from which a train can be operated. As dedicated vehicles or regular passenger cars, they have one or two driver compartm ...
, 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
Pendolino (from Italian ''pendolo'' "pendulum", and ''-ino,'' a diminutive suffix) is an Italian family of tilting trains used in Italy, Spain, Germany, Poland, Portugal, Slovenia, Finland, Russia, the Czech Republic, Slovakia, the UK, the US, ...
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 conglome ...
,
Shinkansen
The , colloquially known in English as the bullet train, is a network of high-speed railway lines in Japan. Initially, it was built to connect distant Japanese regions with Tokyo, the capital, to aid economic growth and development. Beyond l ...
in Japan, the
China Railway High-speed in China,
ICE 3
ICE 3, or Intercity-Express 3, is a family of high-speed electric multiple unit trains operated by Deutsche Bahn. It includes classes 403, 406, 407 and 408, which are known as ICE 3, ICE 3M, New ICE 3 and ICE 3neo respectively. Three multisystem ...
in Germany, and the British Rail
class 395 Javelin. The retired New York–Washington ''
Metroliner'' service, first operated by the
Pennsylvania Railroad and later by
Amtrak
The National Railroad Passenger Corporation, doing business as Amtrak () , is the national passenger railroad company of the United States. It operates inter-city rail service in 46 of the 48 contiguous U.S. States and nine cities in Canada ...
, also featured high-speed electric multiple-unit cars, known as the
Budd Metroliner.
Fuel cell development
EMUs powered by
fuel cells 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 equipm ...
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 ...
. An example is
Alstom’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 ...
-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
In transportation, hydrail is the generic term describing all forms of rail vehicles, large or small, which use on-board hydrogen fuel as a source of energy to power the traction motors, or the auxiliaries, or both. Hydrail vehicles use the chem ...
has been coined for hydrogen-powered rail vehicles.
Battery electric multiple unit
Many
battery electric multiple units 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 g ...
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
Eddy currents (also called Foucault's currents) are loops of electrical current induced within conductors by a changing magnetic field in the conductor according to Faraday's law of induction or by the relative motion of a conductor in a magnet ...
,
rheostatic and/or
regenerative braking
Regenerative braking is an energy recovery mechanism that slows down a moving vehicle or object by converting its kinetic energy into a form that can be either used immediately or stored until needed. In this mechanism, the electric traction mo ...
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
The New Generation Rollingstock (NGR) is a class of individually-propelled carriages ("electric multiple units") manufactured by Bombardier Transportation in Savli, India for the Queensland Rail City network that entered service between Decembe ...
train in the Queensland Rail City network
The Queensland Rail Citytrain network, provides urban, suburban and interurban electric passenger railway services in South East Queensland, Australia.
History
The first railway in Queensland did not run to Brisbane, but ran from Ipswich to ...
, Australia
File:ICE 3 Oberhaider-Wald-Tunnel.jpg, A Deutsche Bahn ICE 3
ICE 3, or Intercity-Express 3, is a family of high-speed electric multiple unit trains operated by Deutsche Bahn. It includes classes 403, 406, 407 and 408, which are known as ICE 3, ICE 3M, New ICE 3 and ICE 3neo respectively. Three multisystem ...
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
Flirting or coquetry is a social and sexual behavior involving spoken or written communication, as well as body language. It is either to suggest interest in a deeper relationship with the other person or, if done playfully, for amusement.
I ...
-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 ...
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. Gal ...
'' in Switzerland
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 tes ...
File:483008 at Smallbrook Junction in 2020.jpg, A British Rail Class 483
The British Rail Class 483 electric multiple units were originally built as 1938 tube stock units for London Underground. They were extensively refurbished between 1989 and 1992 by Eastleigh Works, for use on services on the Isle of Wight's Isl ...
at Smallbrook Junction on the Isle of Wight
The Isle of Wight ( ) is a Counties of England, county in the English Channel, off the coast of Hampshire, from which it is separated by the Solent. It is the List of islands of England#Largest islands, largest and List of islands of England#Mo ...
. 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 tota ...
Vande Bharat Express
The Vande Bharat Express, previously known as Train 18, is a semi-high-speed, electric multiple unit train operated by Indian Railways. It was designed and manufactured by the Integral Coach Factory, Chennai. The first train was manufactured in ...
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
The is a commuter and suburban electric multiple unit (EMU) train type developed by East Japan Railway Company (JR East) from the earlier E231 series and the E531 series design. The first train was introduced in December 2006 for use on the C ...
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
The MI 09 (French: ''Matériel d'Interconnexion de 2009'', English: ''interconnection rolling stock of 2009'') is a double-deck, dual-voltage electric multiple unit trainset that is operated on line A of the Réseau Express Régional (RER), a ...
on RER A Line in November 2012
File:KTM Class 93 Pulau Sebang 015347.jpg, KTM Class 93 of KTM ETS
The KTM ETS (commercially known as ETS, short for 'Electric Train Service') is an inter-city rail passenger service operated by Keretapi Tanah Melayu (KTM) using electric multiple-unit (EMU) trains. The KTM ETS is the second electric train servic ...
arriving Pulau Sebang
Pulau Sebang is a mukim and town in Alor Gajah District, Malacca, Malaysia, which borders Tampin town of Tampin District, Negeri Sembilan.
Infrastructures
* Aleyah Kuala Ina Mosque
* Mydin Pulau Sebang
* SMK Sultan Mansor Shah
Transportati ...
File:Скоростной_поезд_"Хендай".jpg, HRCS2 of the Ukrainian Railways
Ukrainian Railways ( uk, Укрзалізниця, Ukrzaliznytsia, abbreviated as UZ) is a state-owned joint-stock company of rail transport in Ukraine, a monopoly that controls the vast majority of the railroad transportation in the country. ...
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 using ...
*
Diesel multiple unit
*
Battery electric multiple unit
A battery electric multiple unit (BEMU), battery electric railcar or accumulator railcar is an electrically driven multiple unit or railcar whose energy is derived from rechargeable batteries driving the traction motors.
Prime advantages of these ...
*
British electric multiple units
References
{{DEFAULTSORT:Electric Multiple Unit
Multiple units
Electric rail transport