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Acurrent collector (often called a "pickup") is a device used introlleybuses,trams,electric locomotives andEMUs to carryelectric power (current) fromoverhead lines, electricthird rails, orground-level power supplies to the electrical equipment of the vehicles. Those for overhead wires are roof-mounted devices, those for rails are mounted on thebogies.
Typically, electric current connectors have one or more spring-loaded arms that press a collector or contact shoe against the rail or overhead wire. As the vehicle moves, the contact shoe slides along the wire or rail to draw the electricity needed to run the vehicle's motor.
The current collector arms areelectrically conductive but mountedinsulated on the vehicle's roof, side or base. An insulated cable connects the collector with theswitch,transformer ormotor. Thesteel rails of thetracks act as theelectrical return.
Electric vehicles that collect their current from anoverhead line system use different forms of one- or two-armpantograph collectors,bow collectors ortrolley poles. The current collection device presses against the underside of the lowest wire of an overhead line system, which is called acontact wire.
Most overhead supply systems are either DC or single phase AC, using a single wire with return through the grounded running rails.Three phase AC systems use a pair of overhead wires, and pairedtrolley poles.
Electric overhead cranes andgantry cranes may use a current collector system to provide power over the full length of their operating area. The current collector assembly use sliding shoes that run on rails. Depending on the size of crane, contact rails may be copper wires, copper bars, or steel channels. mounted on insulating supports. Two rails are used for DC supply, and three for three-phase AC, with grounding of the crane through contact with the runway rails. The contact rails are mounted out of the reach of people working in the area to prevent an electric shock hazard.
![Bumper cars at Taunus Wunderland [de] showing collector poles.](/mt/?noimg=&dark=on&url=http%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aAutoscooter1.jpg)
Thetrolley pole wheel is agrooved contact wheel mounted on top of the trolley pole instead of a trolley shoe. The trolley pole wheel somewhat resembles apulley. Trolley pole wheels are now rarely used.
Acollector pole is the pole at the end of abumper car. It has a contact shoe on top.
Electric railways withthird rails orfourth rails carry collector or contact shoes, projecting laterally (sideways), or vertically, from theirbogies. The contact shoe may slide on top of the third rail (top running), on the bottom (bottom running) or on the side (side running). The side running contact shoe is used against theguide bars onrubber-tired metros. A vertical contact shoe is used onfourth rail systems. A pair of contact shoes was used onunderground current collection systems. Contact shoes may also be used onoverhead conductor rails, onguide bars or ontrolley wires in the case oftrams ortrolleybuses. Most railways usethree rails, while theLondon Underground usesfour rails. Trams or trolleybuses use agrooved trolley shoe at the end of atrolley pole. A contact shoe is used as aground on the runningrail of a rubber-tired metro.
A long and narrow contact shoe shaped like aski, or "skid" or "ski collector" or "contact ski", was historically used onstud contact systems so it maintains contact with small studs in the road placed at large intervals. A single ski was as long as 12 feet (3.7 m) in some systems.[1]: 107–116 Stud contact systems were short-lived due to safety issues with the studs. They were supposed to be electrified only when compatible vehicles passed over them, but the studs often malfunctioned and remained electrified continuously, posing an electrocution hazard.[2]
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