British Rail Class 320
Overview
 
The British Rail Class 320 is an alternating current
Alternating current
In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....

 (AC) electric multiple unit
Electric multiple unit
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...

 (EMU) train
Train
A train is a connected series of vehicles for rail transport that move along a track to transport cargo or passengers from one place to another place. The track usually consists of two rails, but might also be a monorail or maglev guideway.Propulsion for the train is provided by a separate...

 found on the Strathclyde Partnership for Transport
Strathclyde Partnership for Transport
The Strathclyde Partnership for Transport is a public body which is responsible for planning and co-ordinating regional transport, and especially the public transport system, in the Strathclyde area of western Scotland...

 (SPT) rail network in Central Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

, and is used exclusively on the North Clyde Line
North Clyde Line
The North Clyde Line is a suburban railway in West Central Scotland. The route is operated by First ScotRail, on behalf of Transport Scotland...

 between Helensburgh
Helensburgh
Helensburgh is a town in Argyll and Bute, Scotland. It lies on the north shore of the Firth of Clyde and the eastern shore of the entrance to the Gareloch....

 and Airdrie, North Lanarkshire
Airdrie, North Lanarkshire
Airdrie is a town within North Lanarkshire, Scotland. It lies on a plateau roughly 400 ft above sea level, and is approximately 12 miles east of Glasgow city centre. Airdrie forms part of a conurbation with its neighbour Coatbridge, in the former district known as the Monklands. As of 2006,...

 via Glasgow Queen Street railway station
Glasgow Queen Street railway station
Glasgow Queen Street is a railway station in Glasgow, Scotland, the smaller of the city's two main line railway termini and the third-busiest station in Scotland. It is between George Street to the south and Cathedral Street Bridge to the north, at the northern end of Queen Street adjacent to...

.
The Class 320 is effectively a 3-car derivative of the Class 321
British Rail Class 321
The British Rail Class 321 alternating current electric multiple units were built by BREL York in three batches from 1988-91. The design was successful and led to the development of the similar Class 320 and Class 322 units for use by Strathclyde PTE and Stansted Express respectively...

 units found in and around 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...

 and the Midlands. Built in 1990 by BREL
BREL
British Rail Engineering Limited , was the railway systems engineering division of British Rail, until the design and building of trains in the UK was privatised in 1993. On 31 October 1969, the company was incorporated as British Rail Engineering Limited.-Main products:The vast majority of BREL's...

 in York
York
York is a walled city, situated at the confluence of the Rivers Ouse and Foss in North Yorkshire, England. The city has a rich heritage and has provided the backdrop to major political events throughout much of its two millennia of existence...

, 22 3-car sets were ordered by SPT to supersede the aging Class 303
British Rail Class 303
The British Rail Class 303 electric multiple units, also known as "Blue Train" units, were introduced in 1960 for the electrification of the North Clyde and the Cathcart Circle lines in Strathclyde...

 and Class 311
British Rail Class 311
The British Rail Class 311 alternating current electric multiple units were built by Cravens at Sheffield in 1967. They were intended for use on the line from to and , which was electrified in 1967.-Appearance:...

 stock which were by then 30 years old.

The units run on 25 kV
Volt
The volt is the SI derived unit for electric potential, electric potential difference, and electromotive force. The volt is named in honor of the Italian physicist Alessandro Volta , who invented the voltaic pile, possibly the first chemical battery.- Definition :A single volt is defined as the...

 AC overhead line supply via a Brecknell Willis High Speed pantograph, then routed to the transformer and then finally onto the four Brush TM2141B traction motors.
 
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