An electric multiple unit or EMU is a multiple-unittrain 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. 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. 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.[1] 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.
Multiple unit train control was first used in the 1890s.
The Liverpool Overhead Railway opened in 1893 with two-car electric multiple units,[2] controllers in cabs at both ends directly controlling the traction current to motors on both cars.[3]
The multiple unit traction control system was developed by Frank Sprague and first applied and tested on the South Side Elevated Railroad (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.
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.
Motor cars carry the traction motors 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 cars 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 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.
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.
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
^N. K. De (2004). Electric Drives. PHI Learning Pvt. Ltd. 8.4 "Electric traction", p.84. ISBN9788120314924.
^"Liverpool Overhead Railway motor coach number 3, 1892". National Museums Liverpool. Retrieved 2011-01-21. This is one of the original motor coaches which has electric motors mounted beneath the floor, a driving cab at one end and third class accommodation with wooden seats.
^"What you need to know about Alstom's hydrogen-powered Coradia iLint - Global Rail News". globalrailnews.com. 24 October 2017.
^Hata, Hiroshi. (PDF). Railway Technology Today. Archived from the original (PDF) on 1 November 2021. Retrieved 13 March 2022.
External links
Media related to Electric multiple units, motor coaches and railcars at Wikimedia Commons
March 16, 2023
electric, multiple, unit, this, article, needs, additional, citations, verification, please, help, improve, this, article, adding, citations, reliable, sources, unsourced, material, challenged, removed, find, sources, news, newspapers, books, scholar, jstor, d. This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Electric multiple unit news newspapers books scholar JSTOR December 2009 Learn how and when to remove this template message 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 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 The great majority of EMUs are passenger trains but versions also exist for carrying mail A Liverpool Overhead Railway carriage in the Museum of Liverpool The first EMUs in 1893 The prototype unit of JNR 201 series on public display at Harajuku Station in Tokyo 13 May 1979 Next to it a Yamanote Line s 103 series train can be seen passing through DART 8500 class commuter EMU at Howth Junction railway station Ireland A high speed EMU CR400BF G operated by China Railway High speed at Beijing Chaoyang railway station EMUs are popular on commuter and suburban rail networks around the world due to their fast acceleration and pollution free operation 1 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 Contents 1 History 2 Types 3 As high speed trains 4 Fuel cell development 5 Battery electric multiple unit 6 Comparison with locomotives 7 See also 8 References 9 External linksHistory EditMultiple unit train control was first used in the 1890s The Liverpool Overhead Railway opened in 1893 with two car electric multiple units 2 controllers in cabs at both ends directly controlling the traction current to motors on both cars 3 The multiple unit traction control system was developed by Frank Sprague and first applied and tested on the South Side Elevated Railroad 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 Edit Metro North Railroad M8 married pairs in Port Chester New York 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 for overhead systems and transformers Motor cars carry the traction motors 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 cars 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 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 EditSome of the more famous electric multiple units in the world are high speed trains the Italian Pendolino and Frecciarossa 1000 Shinkansen in Japan the China Railway High speed 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 and later by Amtrak also featured high speed electric multiple unit cars known as the Budd Metroliner Fuel cell development EditEMUs powered by fuel cells are under development If successful this would avoid the need for an overhead line or third rail An example is Alstom s hydrogen powered Coradia iLint 4 The term hydrail has been coined for hydrogen powered rail vehicles Battery electric multiple unit EditMany 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 EditEMUs when compared with electric locomotives offer 5 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 carsSee also EditElectro diesel multiple unit Diesel multiple unit Battery electric multiple unit British electric multiple unitsReferences Edit N K De 2004 Electric Drives PHI Learning Pvt Ltd 8 4 Electric traction p 84 ISBN 9788120314924 Liverpool Overhead Railway motor coach number 3 1892 National Museums Liverpool Retrieved 2011 01 21 This is one of the original motor coaches which has electric motors mounted beneath the floor a driving cab at one end and third class accommodation with wooden seats Frank Sprague 18 January 1902 Mr Sprague answers Mr Westinghouse The New York Times Retrieved 16 June 2012 What you need to know about Alstom s hydrogen powered Coradia iLint Global Rail News globalrailnews com 24 October 2017 Hata Hiroshi What Drives Electric Multiple Units PDF Railway Technology Today Archived from the original PDF on 1 November 2021 Retrieved 13 March 2022 External links Edit Media related to Electric multiple units motor coaches and railcars at Wikimedia Commons Retrieved from https en wikipedia org w index php title Electric multiple unit amp oldid 1142763725, wikipedia, wiki, book, books, library,
