- Pantograph (rail)
A pantograph is a device that collects electric current from
overhead linesfor electric trains or trams. The term stems from the resemblance to pantograph devices for copying writing and drawings.
A flat side-pantograph was invented 1895 at the Baltimore & Ohio Railroad [ [http://de.wikipedia.org/wiki/Bild:Mining_locomotive_1895.jpgEarly 1895 flat pantograph on mining locomotive] ] and in Germany 1900 by Siemens & Halske.
According to the late rail historian Harre Demoro, the pantograph was invented by the
Key Systemshops for their commuter trains in the East Bay section of the San Francisco Bay Areain California. They appear in photographs of the first day of service in 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.
However, the most common type 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
TGVto low-speed urban tram systems. The design operates with equal efficiency in either direction of motion, as demonstrated by the Swiss and Austrian railways whose newest high performance locomotives, the Re 460 and Taurus respectively, operate with them set in opposite directions.
The electric transmission system for modern electric rail systems consists of an upper load 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 return.
As the train moves, the contact shoe slides along the wire and can set up acoustical
standing waves 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 poles, which were widely used on early streetcar systems and still are used by trolleybuses, 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-rail system, they allow the use of higher voltages.
ingle- 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 Transit] encountered a whole bunch of wire downings on the Northeast Corridor Branch ( New York City- Trenton, NJ) before they decided to replace the pantographs on Arrow-III trainswith a more forgiving dual arm design, possibly in 1991...." [ [http://www.subchat.com/read.asp?Id=265088 Re: which is Arrow 1 which is arrow 2? ] ]
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 poles or single-arm pantographs.
Metro systems and overhead lines
rapid transitsystems are powered by a third rail, 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 sol which only applies power to segments of track that are completely covered by the tram. This system is used in the historic centre of Bordeauxwhere an overhead wire system would cause a visual intrusion.
Railway electrification system
Wikimedia Foundation. 2010.
Look at other dictionaries:
Pantograph (disambiguation) — Pantograph may refer to:* Pantograph, a duplication instrument * Pantograph (rail), the device that collects electric current from overhead lines for electric trains or trams * Pantographic knife, a folding knife whose blade is opened by a unique … Wikipedia
British Rail Class 313 — A refreshed Southern Class 313 No. 313203 at Brighton on the West Coastway Line … Wikipedia
Third rail — For other uses, see Third rail (disambiguation). Third rail at the West Falls Church Metro station near Washington, D.C., electrified at 750 volts. The third rail is at the top of the image, with a white canopy above it. The two lower rails… … Wikipedia
British Rail Class 317 — A newly repainted National Express East Anglia Class 317/5 No. 317505 at London Liverpool Street … Wikipedia
British Rail Class 319 — First Capital Connect refreshed Class 319/3 EMUs No. 319369 and 319368 at St. Albans The refreshed i … Wikipedia
Manila Light Rail Transit System — Overview Type … Wikipedia
British Rail Class 377 — Electrostar Southern Class 377/2 no. 377207 at Hemel Hempstead with a service from Milton Keynes Central to South Croydon … Wikipedia
British Rail Class 323 — London Midland Class 323 No. 323220 at Birmingham In service 1992 present Manufacturer … Wikipedia
British Rail Class 373 — Infobox EMU name = British Rail Class 373 Eurostar imagesize = 300px caption = background = #FFCF81 Manufacturer = GEC Alsthom Family = TGV Operator = Eurostar SNCF Formation = 20 cars (Three Capitals) 16 cars (North of London) Built = 31… … Wikipedia
British Rail Class 71 — Infobox Locomotive name = British Rail Class 71 powertype = Electric caption = E5001 at Doncaster Works. builder = British Railways’ Doncaster Works builddate = 1958–1960 totalproduction = 24 gauge = RailGauge|ussg|lk=on|al=on wheeldiameter =… … Wikipedia