A
pantograph is a device that collects electric current from
overhead linesOverhead lines or overhead wires are used to transmit electrical energy to trams, trolleybuses or trains at a distance from the energy supply point...
for electric
trainA train is a connected series of vehicles for rail transport that move along a track to transport freight or passengers from one place to another. The track usually consists of two rails, but might also be a monorail or maglev guideway....
s or
tramA tram, tramcar, trolley, trolleycar, or streetcar is a railborne vehicle, of lighter weight and construction than a conventional train, designed for the transport of passengers within, close to, or between villages, towns and/or cities, on tracks running primarily on streets...
s. The term stems from the resemblance to
pantograph devicesA pantograph is a mechanical linkage connected in a special manner based on parallelograms so that the movement of one specified point is an amplified version of the movement of another point...
for copying writing and drawings.
A flat side-pantograph was invented in 1895 at the Baltimore & Ohio Railroad and in Germany in 1900 by
SiemensSiemens AG is a German electrical and telecommunications companysiemens may refer to*siemens , the SI unit of electrical conductance, equivalent to 1 ampere/voltSiemens may also refer to:...
& Halske.
The familiar diamond-shaped roller pantograph was invented by John Q. Brown of the
Key SystemThe Key System was a privately owned company which provided mass transit in the cities of Oakland, Berkeley, Alameda, Emeryville, Piedmont, San Leandro, Richmond, Albany and El Cerrito in the eastern San Francisco Bay Area from 1903 until 1960, when the system was sold to a newly formed public...
shops for their
commuterCommuting is regular travel between one's place of residence and place of work or full time study. Institutions that have few dormitories or near-campus student housing are called commuter schools in the United States....
trains which ran between
San FranciscoSan Francisco is the fourth most populous city in California and the 12th most populous city in the United States, with a 2008 estimated population of 808,976. It is the eighth most densely populated city in the U.S. and is the financial, cultural, and transportation center of the larger San...
and the
East BayThe East Bay is a region of the San Francisco Bay Area, California, United States and comprises both Alameda and Contra Costa Counties. It lies on the eastern shores of the San Francisco Bay and San Pablo Bay...
section of the
San Francisco Bay AreaThe San Francisco Bay Area, commonly known as the Bay Area, or the Yay Area, is a metropolitan region that surrounds the San Francisco and San Pablo estuaries in Northern California. The region encompasses large cities such as San Francisco, Oakland, and San Jose, along with smaller urban and...
in
CaliforniaCalifornia is the most populous state in the United States, and the third largest by area. California is the second most populous sub-national entity in the Americas, behind only São Paulo, Brazil...
.
A
pantograph is a device that collects electric current from
overhead linesOverhead lines or overhead wires are used to transmit electrical energy to trams, trolleybuses or trains at a distance from the energy supply point...
for electric
trainA train is a connected series of vehicles for rail transport that move along a track to transport freight or passengers from one place to another. The track usually consists of two rails, but might also be a monorail or maglev guideway....
s or
tramA tram, tramcar, trolley, trolleycar, or streetcar is a railborne vehicle, of lighter weight and construction than a conventional train, designed for the transport of passengers within, close to, or between villages, towns and/or cities, on tracks running primarily on streets...
s. The term stems from the resemblance to
pantograph devicesA pantograph is a mechanical linkage connected in a special manner based on parallelograms so that the movement of one specified point is an amplified version of the movement of another point...
for copying writing and drawings.
Invention
A flat side-pantograph was invented in 1895 at the Baltimore & Ohio Railroad and in Germany in 1900 by
SiemensSiemens AG is a German electrical and telecommunications companysiemens may refer to*siemens , the SI unit of electrical conductance, equivalent to 1 ampere/voltSiemens may also refer to:...
& Halske.
The familiar diamond-shaped roller pantograph was invented by John Q. Brown of the
Key SystemThe Key System was a privately owned company which provided mass transit in the cities of Oakland, Berkeley, Alameda, Emeryville, Piedmont, San Leandro, Richmond, Albany and El Cerrito in the eastern San Francisco Bay Area from 1903 until 1960, when the system was sold to a newly formed public...
shops for their
commuterCommuting is regular travel between one's place of residence and place of work or full time study. Institutions that have few dormitories or near-campus student housing are called commuter schools in the United States....
trains which ran between
San FranciscoSan Francisco is the fourth most populous city in California and the 12th most populous city in the United States, with a 2008 estimated population of 808,976. It is the eighth most densely populated city in the U.S. and is the financial, cultural, and transportation center of the larger San...
and the
East BayThe East Bay is a region of the San Francisco Bay Area, California, United States and comprises both Alameda and Contra Costa Counties. It lies on the eastern shores of the San Francisco Bay and San Pablo Bay...
section of the
San Francisco Bay AreaThe San Francisco Bay Area, commonly known as the Bay Area, or the Yay Area, is a metropolitan region that surrounds the San Francisco and San Pablo estuaries in Northern California. The region encompasses large cities such as San Francisco, Oakland, and San Jose, along with smaller urban and...
in
CaliforniaCalifornia is the most populous state in the United States, and the third largest by area. California is the second most populous sub-national entity in the Americas, behind only São Paulo, Brazil...
. They appear in photographs of the first day of service October 26, 1903. For many decades thereafter, the same diamond shape was used by electric rail systems around the world, and remains in use by some today.
The pantograph was an improvement on the simple
trolley poleA trolley pole is a tapered cylindrical pole of wood or metal, used to transfer electricity from a "live" overhead wire to the control and propulsion equipment of a tram or trolley bus. The use of overhead wire in a system of current collection is reputed to be the 1880 invention of Frank J....
which prevailed up to that time primarily because it allowed an electric rail vehicle to travel at higher speeds without losing contact with the
catenaryOverhead lines or overhead wires are used to transmit electrical energy to trams, trolleybuses or trains at a distance from the energy supply point...
.
Modern use
The most common type of pantograph today is the so called half-pantograph (sometimes 'Z'-shaped), which has evolved to provide a more compact and responsive single arm design at high speeds as trains get faster. The half-pantograph can be seen in use on everything from the very fastest trains such as the
TGVThe TGV is France's high-speed rail service, currently operated by VFE, the long-distance rail branch of SNCF, the French national rail operator. It was developed during the 1970s by GEC-Alsthom and SNCF, and is now operated primarily by SNCF...
to low-speed urban tram systems. The design operates with equal efficiency in either direction of motion, as demonstrated by the
SwissSwiss Federal Railways is the national railway company of Switzerland headquartered in Berne...
and
AustrianThe Austrian Federal Railways is the national railway system of Austria. Additionally it administers Liechtenstein's railway system....
railways whose newest high performance locomotives, the Re 460 and
TaurusThe EuroSprinter family of electric locomotives is a modular concept of locomotives for the European market built by Siemens. The internal Siemens product name is ES 64, with ES for EuroSprinter and the number 64 indicating the 6,400 kW power at rail.Additional information is given in the name on...
respectively, operate with them set in opposite directions.
Technical details
The electric transmission system for modern electric rail systems consists of an upper weight carrying wire (known as a catenary) from which is suspended a contact wire. The pantograph is spring loaded and pushes a contact shoe up against the contact wire to draw the electricity needed to run the train. The steel rails on the tracks act as the
electrical returnIn electrical engineering, ground or earth may be the reference point in an electrical circuit from which other voltages are measured, or a common return path for electric current, or a direct physical connection to the Earth....
.
As the train moves, the contact shoe slides along the wire and can set up acoustical
standing waveA standing wave, also known as a stationary wave, is a wave that remains in a constant position. This phenomenon can occur because the medium is moving in the opposite direction to the wave, or it can arise in a stationary medium as a result of interference between two waves traveling in opposite...
s in the wires which break the contact and degrade current collection. This means that on some systems adjacent pantographs are not permitted. Pantographs are the successor technology to
trolley poleA trolley pole is a tapered cylindrical pole of wood or metal, used to transfer electricity from a "live" overhead wire to the control and propulsion equipment of a tram or trolley bus. The use of overhead wire in a system of current collection is reputed to be the 1880 invention of Frank J....
s, which were widely used on early streetcar systems and still are used by
trolleybusA trolleybus is an electric bus that draws its electricity from overhead wires using spring-loaded trolley poles...
es, whose freedom of movement and need for a two-wire circuit makes pantographs impractical.
Pantographs with overhead wires are now the dominant form of current collection for modern electric trains because, although more expensive and fragile than a
third-railA third rail is a method of providing electric power to a railway train, through a 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 fully...
system, they allow the use of higher voltages.
Pantographs are typically operated by compressed air from the vehicle's braking system, either to raise the unit and hold it against the conductor or, when springs are used to effect the extension, to lower it. As a precaution against loss of pressure in the second case, the arm is held in the down position by a catch. For high-voltage systems, the same air supply is used to "blow out" the
electric arcAn electric arc is an electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive media such as air. A synonym is arc discharge. The phenomenon was first described by Vasily V. Petrov, a Russian scientist who discovered...
when roof-mounted circuit breakers are used.
Single- and double-arm pantographs
Pantographs may have either a single or a double arm. Double arm pantographs are usually heavier, requiring more power to raise and lower, but may also be more fault tolerant. For example, "...
[New Jersey TransitThe New Jersey Transit Corporation is a statewide public transportation system serving the state of New Jersey, United States, and Orange and Rockland counties in New York...
encountered numerous wire downings on the
Northeast CorridorThe Northeast Corridor is the busiest passenger rail line in the United States by ridership and service frequency. The route is fully electrified and serves a densely urbanized string of cities from Washington, D.C., in the south through Baltimore, Wilmington, Philadelphia, Trenton, Newark, New...
Branch (
New York CityNew York is the most populous city in the United States, and the center of the New York metropolitan area, which is among the most populous urban areas in the world. A leading global city, New York exerts a powerful influence over worldwide commerce, finance, culture, fashion and entertainment...
- Trenton, NJ) before they decided to replace the pantographs on Arrow-III trains with a more forgiving dual arm design, possibly in 1991..."
On railways of the former USSR, the most widely used pantographs are those with a double arm ("made of two rhombs"), but since the late 1990s there have been some single-arm pantographs on Russian railways. Some streetcars use double-arm pantographs, among them the Russian KTM-5, KTM-8, LVS-86 and many other Russian-made trams, as well as some Euro-PCC trams in Belgium. American streetcars use either
trolley poleA trolley pole is a tapered cylindrical pole of wood or metal, used to transfer electricity from a "live" overhead wire to the control and propulsion equipment of a tram or trolley bus. The use of overhead wire in a system of current collection is reputed to be the 1880 invention of Frank J....
s or single-arm pantographs.
Metro systems and overhead lines
Most
rapid transitA rapid transit, metro, subway, underground, or elevated railway system is an electric passenger railway in an urban area with high capacity and frequency, and which is grade separated from other traffic. Rapid transit systems are typically either in underground tunnels or elevated above street level...
systems are powered by a
third railA third rail is a method of providing electric power to a railway train, through a 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 fully...
, but some use pantographs, particularly ones that involve extensive above-ground running. Hybrid metro-tram or 'pre-metro' lines whose routes include tracks on city streets or in other publicly-accessible areas, such as the MBTA Green Line, must of course use overhead wire, since a third rail would normally present too great a risk of electrocution.
The only current exception to this is the new Bordeaux tram system which uses a system called
alimentation par solGround-level power supply, also known as surface current collection and Alimentation par Sol is a modern method of third-rail electrical pick-up for street trams. It was invented for the Bordeaux tramway, which was constructed from 2000 and opened in 2003...
which only applies power to segments of track that are completely covered by the tram. This system is used in the historic centre of
Bordeauxis a port city on the Garonne River in southwest France, with one million inhabitants in its metropolitan area at a 2008 estimate. It is the capital of the Aquitaine region, as well as the prefecture of the Gironde department...
where an overhead wire system would cause a visual intrusion.
Overhead pantographs are sometimes used as alternatives to third rails because third rails can ice over in certain winter weather conditions. The MBTA Blue Line or the
Wonderland LineWonderland is the northern terminus of the Blue Line in the Massachusetts Bay Transportation Authority mass transit system serving greater Boston. The station is located near the Wonderland Greyhound Park in Revere, Massachusetts, and is handicapped accessible. See MBTA accessibility...
uses pantograph power for all of its surface route.
The
Oslois the capital and largest city in Norway. Founded around 1048 by King Harald III of Norway, the town was largely destroyed by a fire in 1624. The Danish–Norwegian king Christian IV rebuilt the city as Christiania . Oslo, then an alternative name, became official again in 1925...
metro line 1 changes from third rail to overhead line power at Frøen station. Due to the many level crossings, it was deemed difficult to install a third rail on the rest of the older line 1 tracks .
See also
- Bow collector
A bow collector is one of the three main devices used on tramcars to transfer electric current from the wires above to the tram below. While once very common in continental Europe, it has now been largely replaced by the pantograph.- Origins:...
- Trolley pole
A trolley pole is a tapered cylindrical pole of wood or metal, used to transfer electricity from a "live" overhead wire to the control and propulsion equipment of a tram or trolley bus. The use of overhead wire in a system of current collection is reputed to be the 1880 invention of Frank J....
- Third rail
A third rail is a method of providing electric power to a railway train, through a 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 fully...
- 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...
- Railway electrification system
A railway electrification system supplies electrical energy to railway locomotives and multiple units so that they can operate without having an on-board prime mover. There are several different electrification systems in use throughout the world...