London Underground 1995 Stock

1995 Stock
A Northern line 1995 Stock at Mornington Crescent
The interior of a refurbished 1995 Stock
In service	1998–present
Manufacturer	GEC Alsthom (now Alstom)[1]
Replaced	1959 Stock 1962 Stock MK1 1972 Stock
Constructed	1996–1999[1]
Refurbishment	2013–2015
Number built	636 cars[1]
Formation	6 cars per trainset
Capacity	662 per trainset
Line(s) served	Northern
Specifications
Car length	17.77 m (58 ft 3.6 in)
Width	2.630 m (8 ft 7.54 in)
Height	2.875 m (9 ft 5.19 in)
Maximum speed	100 km/h (62 mph), limited to 72 km/h (45 mph) due to poor track condition in the underground sections of the line
Weight	DM 29.4 tonnes (28.9 long tons; 32.4 short tons) UNDM 27.9 tonnes (27.5 long tons; 30.8 short tons) T 21.5 tonnes (21.2 long tons; 23.7 short tons)
Traction system	IGBT-VVVF (Alstom ONIX)[1]
Traction motors	3 phase induction motor (Alstom)[1]
Bogies	Twin-transform flexible frame bogies (Adtranz)[1]
Seating	200 per trainset
Stock type	Deep-level tube
Notes
London transport portal

The London Underground 1995 Stock is a type of rolling stock used 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^[2] replacing old 1959 Stock, 1962 Stock and 1972 Stock (Mark 1).

The trains are the only deep-level tube stock to use selective door opening, necessitated by short platforms at stations such as Moorgate, Charing Cross, Hampstead and Clapham Common.

Construction and entry into service

The 106 six-car trains were built by GEC Alsthom (later Alstom) at their plant in Washwood Heath, Birmingham, although the bodyshells were manufactured in and imported from Spain. Each train is made up of two three-car units, coupled together, with each unit consisting of a Driving Motor car (DM), a Trailer car (T) and an Uncoupling Non-Driving Motor car (UNDM). The six-car trains are therefore formed DM-T-UNDM+UNDM-T-DM. Some trailer cars are equipped with a de-icing tank and applicators, in order to spray de-icing fluid on the current-collection rails; these cars are distinguished by a small circle after their car number.^[3]

Construction began in 1996, with one car going on public display as part of the Lord Mayor's Show on 9 November 1996. The first train was delivered to Ruislip Depot on 20 December 1996, and testing began in early 1997. The trains entered passenger service between 12 June 1998 and 10 April 2001.^[4][5]

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"^[6] 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.

Refurbishment

The original unrefurbished interior of the 1995 Stock

Starting in 2013, the 1995 Stock underwent refurbishment, some 15 years after being introduced. Internally, new flooring was fitted, with contrasting colours in the doorways, and the yellow grab rails were re-painted dark blue. The new standard London Underground "Barman" moquette was also introduced, and wheelchair backboards were installed in the trailer cars. The external door open/close buttons were plated over, and the internal buttons were replaced by a visual door open/close warning light. The windows were polished to remove graffiti, and the external livery was re-applied.^[7][8]

The refurbishment was carried out by Alstom, and the first refurbished train entered service on 30 May 2013. All 106 refurbished trains had entered service by 13 April 2015.^[9]

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.

Train details

• Length per carriage 17.77 m (58 ft 4 in)
• Width per carriage 2.63 m (8 ft 8 in)
• Height 2.875 m (9 ft 5.2 in)^[10]
• Total seating capacity per six-carriage train 200, plus 20 perch seats and 48 tip-up seats. There are also 24 wheelchair spaces.
• Total passenger capacity per six-carriage train 665

Diagram of the front of a 1995 stock train

References

External links

Wikimedia Commons has media related to London Underground 1995 Stock.

• 1995 Tube Stock specifications (TfL)
• 1995 Tube Stock - Squarewheels.org.uk