Railway electric traction
Encyclopedia
Railway electric traction describes the various types of locomotive and multiple units that are used on electrification systems
around the world.
built a small electrical railway, using a dynamo
as the motor and the rails as the current-carrying medium. The electric current
flowed through the metal rim of otherwise wooden wheels, being picked up via contact brushes.
Electrical traction offered several benefits over the then predominant steam
traction, particularly in respect of its quick acceleration (ideal for urban (metro) and suburban (commuter) services) and power (ideal for heavy freight trains through mountainous/hilly sections). A plethora of systems emerged in the first twenty years of the twentieth century.
Another way is to use multi-system locomotives that can operate under several different voltages and current types. In Europe
, it is common to use four-system locomotives (1.5 kV DC, 3 kV DC, 15 kV 16⅔ Hz AC, 25 kV, 50 Hz AC). These locomotives do not have to stop when passing from one electrification system to another, the changeover occurring where the train coasts for a short time.
Eurostar
trains through the Channel Tunnel
are multisystem; a significant part of the route near London
is on southern England's 750 V DC third rail
system, the route into Brussels
is 3000 V DC overhead, while the rest of the route is 25 kV 50 Hz overhead. The need for these trains to use third rail ended upon completion of High Speed 1 in 2007. Southern England has some overhead
/third rail
dual-system locomotives and multiple units to allow through running between 750 V DC third rail south of London and the 25 kV AC overhead north and east of London.
Electro-diesel locomotive
s which can operate as an electric locomotive on electrified lines but have an on-board diesel engine for non-electrified sections or sidings have been used in several countries.
systems but there are no switching stations - the two systems meet at breaks on overhead wires. Only two of the breaks (Kutná Hora and Nedakonice) are in stations.
(commonly about 600 V DC) and overhead systems (a variety of voltages, both DC and AC were used). The third rail systems of this period eventually gave rise to the 750 V DC system in the southern part of the UK and a separate area with the same system around Merseyside.
Cheap loans to stimulate economic development in the 1930s gave rise to the several schemes of 1500 V DC electrification, mostly completed post war, notably between Liverpool Street
and Shenfield, and the Woodhead Line
. Starting with the West Coast Mainline electrification in the 1960s, the 25 kV AC overhead system was adopted for all subsequent mainline electrification in the UK (except for extensions to other existing systems, mostly on the southern third rail network).
In some areas with restricted clearances, particularly in urban areas in east London (converted from 1500 V DC) and on suburban routes around Glasgow, 6.25 kV was used. A system known as "Automatic Power Control" was developed to allow trains to automatically switch between the voltages whilst moving. All the driver had to do was shut off power and coast until clear of the neutral section; the system automatically opened the circuit breaker, detected a change in voltage and switched over the transformer to the correct input voltage setting, then closed the circuit breaker. This system proved somewhat unreliable and, with experience, it was found that less clearance was needed for 25 kV than had initially been allowed for. This allowed the 6.25 kV sections to be converted to 25 kV, with the last section, at the London end of the London Tilbury and Southend line, being converted in 1983.
, New Jersey Transit
uses multisystem ALP-44
and ALP-46 locomotives for its Midtown Direct service into New York
and Amtrak
uses multi-system AEM-7
, HHP-8
and Acela locomotives on the Northeast Corridor between Washington DC and Boston
. In both cases, through trains run on both newer, 25 kV 60 Hz built or refurbished by their respective agencies since the 1980s and older, 12 kV 25 Hz inherited from the now-defunct Pennsylvania Railroad
. The latter dates to the 1930s, when the Pennsylvania upgraded its electrified network from 650 V DC third rail.
The 1500 V DC overhead system (negative earth, positive catenary) is used around Mumbai
. The Mumbai region is the last bastion of 1500 V DC electrified lines on Indian Railways
. There are plans to change this to 25 kV AC by 2010. The 25 kV AC system with overhead lines
is used throughout the rest of the country. The dual-voltage WCAM series locomotives haul intercity trains out of Mumbai
DC suburban region. The new AC/DC EMU rakes used in Mumbai are also designed to operate with both DC and AC traction as the Mumbai area switches over to the 25 kV AC system.
The Kolkata Metro
uses 750 V DC traction with a third rail
for delivering the electricity to the EMUs. The Kolkata trams
use 550 V DC with overhead lines
with underground conductors
. The catenary is at a negative potential.
The Delhi Metro uses 25 kV AC overhead lines
on the ground-level and elevated routes, and uses a rather unusual "rigid catenary", or overhead power rail, in the underground tunnel sections.
and Locomotive
sections.
systems use electric trains, like the Shinkansen
and the TGV
.
Railway electrification system
A railway electrification system supplies electrical energy to railway locomotives and multiple units as well as trams so that they can operate without having an on-board prime mover. There are several different electrification systems in use throughout the world...
around the world.
History
Railway electrification as a means of traction emerged at the end of the nineteenth century, although experiments in electric rail have been traced back to the mid-nineteenth century. Thomas Davenport, in Brandon, Vermont, erected a circular model railroad on which ran battery-powered locomotives (or locomotives running on battery-powered rails) in 1834. Robert Davidson, of Aberdeen, Scotland, created an electric locomotive in 1839 and ran it on the Edinburgh-Glasgow railway at 4 miles per hour. The earliest electric locomotives tended to be battery-powered. In 1880, Thomas EdisonThomas Edison
Thomas Alva Edison was an American inventor and businessman. He developed many devices that greatly influenced life around the world, including the phonograph, the motion picture camera, and a long-lasting, practical electric light bulb. In addition, he created the world’s first industrial...
built a small electrical railway, using a dynamo
Dynamo
- Engineering :* Dynamo, a magnetic device originally used as an electric generator* Dynamo theory, a theory relating to magnetic fields of celestial bodies* Solar dynamo, the physical process that generates the Sun's magnetic field- Software :...
as the motor and the rails as the current-carrying medium. The electric current
Electric current
Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...
flowed through the metal rim of otherwise wooden wheels, being picked up via contact brushes.
Electrical traction offered several benefits over the then predominant steam
Steam locomotive
A steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...
traction, particularly in respect of its quick acceleration (ideal for urban (metro) and suburban (commuter) services) and power (ideal for heavy freight trains through mountainous/hilly sections). A plethora of systems emerged in the first twenty years of the twentieth century.
DC traction units
DC traction units use direct current drawn from either a conductor rail or an overhead line.AC traction units
Apart from a few cases, almost all AC Traction units draw alternating current from an overhead line.Multi-system units
Because of the variety of railway electrification systems, which can vary even within a country, trains often have to pass from one system to another. One way to accomplish this is by changing locomotives at the switching stations. These stations have overhead wires that can be switched from one voltage to another and so the train arrives with one locomotive and then departs with another. Often, however, this is inco.Another way is to use multi-system locomotives that can operate under several different voltages and current types. In Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, it is common to use four-system locomotives (1.5 kV DC, 3 kV DC, 15 kV 16⅔ Hz AC, 25 kV, 50 Hz AC). These locomotives do not have to stop when passing from one electrification system to another, the changeover occurring where the train coasts for a short time.
Eurostar
Eurostar
Eurostar is a high-speed railway service connecting London with Paris and Brussels. All its trains traverse the Channel Tunnel between England and France, owned and operated separately by Eurotunnel....
trains through the Channel Tunnel
Channel Tunnel
The Channel Tunnel is a undersea rail tunnel linking Folkestone, Kent in the United Kingdom with Coquelles, Pas-de-Calais near Calais in northern France beneath the English Channel at the Strait of Dover. At its lowest point, it is deep...
are multisystem; a significant part of the route near London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
is on southern England's 750 V DC third rail
Third rail
A third rail is a method of providing electric power to a railway train, through a semi-continuous rigid conductor placed alongside or between the rails of a railway track. It is used typically in a mass transit or rapid transit system, which has alignments in its own corridors, fully or almost...
system, the route into Brussels
Brussels
Brussels , officially the Brussels Region or Brussels-Capital Region , is the capital of Belgium and the de facto capital of the European Union...
is 3000 V DC overhead, while the rest of the route is 25 kV 50 Hz overhead. The need for these trains to use third rail ended upon completion of High Speed 1 in 2007. Southern England has some overhead
Overhead lines
Overhead lines or overhead wires are used to transmit electrical energy to trams, trolleybuses or trains at a distance from the energy supply point...
/third rail
Third rail
A third rail is a method of providing electric power to a railway train, through a semi-continuous rigid conductor placed alongside or between the rails of a railway track. It is used typically in a mass transit or rapid transit system, which has alignments in its own corridors, fully or almost...
dual-system locomotives and multiple units to allow through running between 750 V DC third rail south of London and the 25 kV AC overhead north and east of London.
Electro-diesel locomotive
Electro-diesel locomotive
An Electro-diesel locomotive is powered either from an electricity supply or by using the onboard diesel engine...
s which can operate as an electric locomotive on electrified lines but have an on-board diesel engine for non-electrified sections or sidings have been used in several countries.
Czech Republic and Slovakia
In the Czech Republic and Slovakia, the railways have both 3,000 V DC and 25 kV AC25 kV AC
The 25 kV Alternating current railway electrification system is commonly used in railways worldwide, especially for high-speed rail.-Overview:This electrification system is ideal for railways that cover long distances and/or carry heavy traffic...
systems but there are no switching stations - the two systems meet at breaks on overhead wires. Only two of the breaks (Kutná Hora and Nedakonice) are in stations.
United Kingdom
Electrification in the UK began in a piecemeal fashion. The earliest main line (as opposed to metro and tramway) systems were divided between low voltage third railThird rail
A third rail is a method of providing electric power to a railway train, through a semi-continuous rigid conductor placed alongside or between the rails of a railway track. It is used typically in a mass transit or rapid transit system, which has alignments in its own corridors, fully or almost...
(commonly about 600 V DC) and overhead systems (a variety of voltages, both DC and AC were used). The third rail systems of this period eventually gave rise to the 750 V DC system in the southern part of the UK and a separate area with the same system around Merseyside.
Cheap loans to stimulate economic development in the 1930s gave rise to the several schemes of 1500 V DC electrification, mostly completed post war, notably between Liverpool Street
Liverpool Street station
Liverpool Street railway station, also known as London Liverpool Street or simply Liverpool Street, is both a central London railway terminus and a connected London Underground station in the north-eastern corner of the City of London, England...
and Shenfield, and the Woodhead Line
Woodhead Line
The Woodhead Line was a railway line linking Sheffield, Penistone and Manchester in the north of England. A key feature of the route is the passage under the high moorlands of the northern Peak District through the Woodhead Tunnels...
. Starting with the West Coast Mainline electrification in the 1960s, the 25 kV AC overhead system was adopted for all subsequent mainline electrification in the UK (except for extensions to other existing systems, mostly on the southern third rail network).
In some areas with restricted clearances, particularly in urban areas in east London (converted from 1500 V DC) and on suburban routes around Glasgow, 6.25 kV was used. A system known as "Automatic Power Control" was developed to allow trains to automatically switch between the voltages whilst moving. All the driver had to do was shut off power and coast until clear of the neutral section; the system automatically opened the circuit breaker, detected a change in voltage and switched over the transformer to the correct input voltage setting, then closed the circuit breaker. This system proved somewhat unreliable and, with experience, it was found that less clearance was needed for 25 kV than had initially been allowed for. This allowed the 6.25 kV sections to be converted to 25 kV, with the last section, at the London end of the London Tilbury and Southend line, being converted in 1983.
United States
In the United StatesUnited States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, New Jersey Transit
New Jersey Transit
The New Jersey Transit Corporation is a statewide public transportation system serving the United States state of New Jersey, and New York, Orange, and Rockland counties in New York State...
uses multisystem ALP-44
ALP-44
The ABB ALP-44 is an electric locomotive which was built by Asea Brown Boveri between 1990 and 1996 and are in operation on the New Jersey Transit and SEPTA railway lines.-New Jersey Transit:...
and ALP-46 locomotives for its Midtown Direct service into New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...
and Amtrak
Amtrak
The National Railroad Passenger Corporation, doing business as Amtrak , is a government-owned corporation that was organized on May 1, 1971, to provide intercity passenger train service in the United States. "Amtrak" is a portmanteau of the words "America" and "track". It is headquartered at Union...
uses multi-system AEM-7
EMD AEM-7
The AEM-7 is a B-B electric locomotive that is used in the United States on the Northeast Corridor between Washington DC and Boston and the Keystone Corridor between Philadelphia and Harrisburg in Pennsylvania. They were built by Electro-Motive Division from 1978 to 1988...
, HHP-8
HHP-8
The Acela HHP-8 is a double-ended electric locomotive manufactured by a consortium of Bombardier and Alstom. HHP-8 stands for High HorsePower 8000...
and Acela locomotives on the Northeast Corridor between Washington DC and Boston
Boston
Boston is the capital of and largest city in Massachusetts, and is one of the oldest cities in the United States. The largest city in New England, Boston is regarded as the unofficial "Capital of New England" for its economic and cultural impact on the entire New England region. The city proper had...
. In both cases, through trains run on both newer, 25 kV 60 Hz built or refurbished by their respective agencies since the 1980s and older, 12 kV 25 Hz inherited from the now-defunct Pennsylvania Railroad
Pennsylvania Railroad
The Pennsylvania Railroad was an American Class I railroad, founded in 1846. Commonly referred to as the "Pennsy", the PRR was headquartered in Philadelphia, Pennsylvania....
. The latter dates to the 1930s, when the Pennsylvania upgraded its electrified network from 650 V DC third rail.
Italy
Italian railways have two systems with overhead supply from a catenary: 3 kV DC and 25 kV AC. The 25 kV AC system is used on the new High speed lines.Spain
Spanish railways have two systems with overhead supply from a catenary: 3 kV DC and 25 kV AC. The 25 kV AC system is used on the High speed lines.India
In India 1500 V DC and 25 kV AC, 50 Hz, is used for main line trains.The 1500 V DC overhead system (negative earth, positive catenary) is used around Mumbai
Mumbai
Mumbai , formerly known as Bombay in English, is the capital of the Indian state of Maharashtra. It is the most populous city in India, and the fourth most populous city in the world, with a total metropolitan area population of approximately 20.5 million...
. The Mumbai region is the last bastion of 1500 V DC electrified lines on Indian Railways
Indian Railways
Indian Railways , abbreviated as IR , is a departmental undertaking of Government of India, which owns and operates most of India's rail transport. It is overseen by the Ministry of Railways of the Government of India....
. There are plans to change this to 25 kV AC by 2010. The 25 kV AC system with overhead lines
Overhead lines
Overhead lines or overhead wires are used to transmit electrical energy to trams, trolleybuses or trains at a distance from the energy supply point...
is used throughout the rest of the country. The dual-voltage WCAM series locomotives haul intercity trains out of Mumbai
Mumbai
Mumbai , formerly known as Bombay in English, is the capital of the Indian state of Maharashtra. It is the most populous city in India, and the fourth most populous city in the world, with a total metropolitan area population of approximately 20.5 million...
DC suburban region. The new AC/DC EMU rakes used in Mumbai are also designed to operate with both DC and AC traction as the Mumbai area switches over to the 25 kV AC system.
The Kolkata Metro
Kolkata Metro
The Kolkata Metro or Calcutta Metro is a mass rapid transit system serving the city of Kolkata and the districts of South 24 Parganas and North 24 Parganas in Indian state of West Bengal. The network consists of one operational line and five lines currently under construction...
uses 750 V DC traction with a third rail
Third rail
A third rail is a method of providing electric power to a railway train, through a semi-continuous rigid conductor placed alongside or between the rails of a railway track. It is used typically in a mass transit or rapid transit system, which has alignments in its own corridors, fully or almost...
for delivering the electricity to the EMUs. The Kolkata trams
Calcutta Tramways Company
The Calcutta Tramways Company Limited is a West Bengal, India government-run company which runs trams in Kolkata and buses in and around Kolkata...
use 550 V DC with overhead lines
Overhead lines
Overhead lines or overhead wires are used to transmit electrical energy to trams, trolleybuses or trains at a distance from the energy supply point...
with underground conductors
Conduit current collection
Conduit current collection is a system of electric current collection used by electric trams, where the power supply is carried in a channel under the roadway, rather than located overhead.-Description:...
. The catenary is at a negative potential.
The Delhi Metro uses 25 kV AC overhead lines
Overhead lines
Overhead lines or overhead wires are used to transmit electrical energy to trams, trolleybuses or trains at a distance from the energy supply point...
on the ground-level and elevated routes, and uses a rather unusual "rigid catenary", or overhead power rail, in the underground tunnel sections.
South Africa
South Africa has 15 km of dual system track, both 3 kV DC and 25 kV AC.Battery electric rail vehicles
A few battery electric railcars and locomotives were used in the twentieth century, but generally the use of battery power was not practical except in underground mining systems, see RailcarRailcar
A railcar, in British English and Australian English, 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 , with a driver's cab at one or both ends. Some railways, e.g., the Great Western...
and Locomotive
Locomotive
A locomotive is a railway vehicle that provides the motive power for a train. The word originates from the Latin loco – "from a place", ablative of locus, "place" + Medieval Latin motivus, "causing motion", and is a shortened form of the term locomotive engine, first used in the early 19th...
sections.
High-speed rail
Many high-speed railHigh-speed rail
High-speed rail is a type of passenger rail transport that operates significantly faster than the normal speed of rail traffic. Specific definitions by the European Union include for upgraded track and or faster for new track, whilst in the United States, the U.S...
systems use electric trains, like the Shinkansen
Shinkansen
The , also known as THE BULLET TRAIN, is a network of high-speed railway lines in Japan operated by four Japan Railways Group companies. Starting with the Tōkaidō Shinkansen in 1964, the network has expanded to currently consist of of lines with maximum speeds of , of Mini-shinkansen with a...
and the TGV
TGV
The TGV is France's high-speed rail service, currently operated by SNCF Voyages, the long-distance rail branch of SNCF, the French national rail operator....
.