In service 1998 - present Formation 6 cars per trainset | Number built 636 cars Capacity 662 per trainset | |
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Replaced 1959 Stock1962 Stock1972 Stock | ||
The 1995 Stock is a type of train on the Northern line of the London Underground. There are 106 six-car trains in operation; they entered service between June 1998 and April 2001 replacing old 1959 Stock and (Mark 1) 1972 Stock.
Contents
It is the only deep-level tube stock to use selective door opening, for example at Moorgate, Charing Cross, Hampstead and Clapham Common.
It used to be operated mainly with a combined power controller, brake lever and dead man's handle at the driver's right hand. When the train is stopped the top of the handle is turned away from the position in which the driver holds it. To depart the driver turned the top of the handle and pushed the red lever forward. However, London Underground introduced TBTC on the Northern line in sections since June 2013. The entire line became TBTC driven in June 2014.
Construction
The stock shares many features with the 1996 Stock used on the Jubilee line: both types were built by Alstom in Birmingham. They have different seating layouts and cab designs, and 1996 Stock is in seven-car trains. Despite the 1995 Stock designation, the step-plates found on the trains read '1996'. It is believed that the 1995 designation served solely to distinguish this stock from the 1996 Stock. Like the 1996 Stock, it had passenger operated door-open controls from new, but these are disabled.
One car was publicly displayed on 9 November 1996 as part of the Lord Mayor's Show; the first train was delivered to Ruislip Depot on 20 December 1996; testing began in early 1997; and they entered passenger service between 12 June 1998 and 10 April 2001.
Traction control
1995 and 1996 stock have similar bodyshells, but they use different AC traction control systems, more modern on 1995 stock since the 1996 stock design spec was 'frozen' in 1991.
1995 stock uses Alstom's "Onix" three-phase insulated-gate bipolar transistor (IGBT) drive, 1996 stock three-phase induction motors fed from a single-source inverter using a gate turn-off thyristor (GTO), derived from those on Class 465 Networker trains.
Earlier Underground stock, like most electric trains until the 1990s, used DC motors. These are now regarded as inefficient, partly because they are traditionally controlled by resistors, and partly because a three-phase AC induction motor is smaller and lighter for the same power. However, in an AC motor maximum torque can only be achieved when the resistance of the rotor windings equals the reactance. AC motors in an industrial setting tend to be operated more or less continuously and therefore large banks of resistors can be used on start-up to raise resistance and maintain torque. This would not be efficient in a small motor designed for stop/start operation. As a result, it was only the invention of electronic control systems from the 1980s onwards that made AC traction viable for trains. The motor can be supplied using an inverter, and by varying the inverter's output frequency it is possible to keep the frequency of the currents flowing in the rotor windings constant, and hence the reactance (while resistance remains fixed).
The GTO used on 1996 stock achieves this by 'chopping' out short pulses of current, whereas modern AC traction such as the 1995 stock uses the IGBT (which is actually an amalgamation of a MOSFET and a conventional transistor), which can switch very high currents very rapidly without damage. In consequence, the 'whine' effect is less noticeable on 1995 stock than on 1996 stock. One disadvantage of IGBTs is that a higher voltage is dropped across them than other devices (high being about ¾ of a volt). As they conduct several thousand amperes, the resultant power dissipated by the IGBTs requires forced-air cooling. The cooling fans can be heard running and then shutting down depending on the amount of voltage being dissipated.
Since October 2007 1995 stock has been fitted with the royal blue seat moquette used on the 1996 and 1973 stocks. The upgrade was completed in early 2008.
Announcer system
The Northern line is fitted with an automated voice announcer. Announcements typically state the station the train has stopped at, the final stop, and connecting London Underground lines and other services.
At stations such as Camden Town (northbound), Charing Cross, Clapham Common (southbound), Euston (southbound), Hampstead (northbound) and Moorgate (southbound), the platform is not long enough to accommodate all doorways of the train, so the 1995 stock is programmed to automatically cut out the first or last set of doors. At these stations, the announcement system advises passengers to move along the carriage to the next set of doors.
Before April, 2016, 1995 Stock was unique in that at stations with interchange to National Rail, the announcer says "Main Line Intercity and Suburban Rail Services" instead of "National Rail services", as on other stock. Interchange announcements were made at stations only, but not between stations. Since April, 2016, the new announcements use "National Rail services" and add interchange information for next station announcement, which are the same as other lines.
Maintenance
1995 stock was operated by Tube Lines / London Underground Ltd (LUL), but is now provided under a Service Provision contract through Northern line Service Provision Ltd (NLSP), an Alstom venture. Maintenance is carried out by Alstom Transport Ltd at Golders Green Traincare Centre in north-west London, behind Golders Green station, and at Morden Traincare Centre in south-west London. There are also "outbases" such as Edgware, High Barnet and Highgate and station fitters based at Kennington and Euston.
2013 refresh
Starting in 2013, the 1995 stock underwent a refresh. This included new flooring, fitting the new standard London Underground seat moquette ('barman'), repainting grab rails dark blue and plating over door open buttons on train exteriors. The trains were also repainted into a slight variation of the standard London Underground livery. The first refurbished train entered service on 30 May 2013. All 106 refurbished trains had entered service by 13 April 2015.