Kawasaki Heavy Industries & Nippon Sharyo C751B

The Kawasaki Heavy Industries & Nippon Sharyo (KNS) C751B is the third generation electric multiple unit rolling stock in operation on the North–South and East–West lines of Singapore's Mass Rapid Transit (MRT) system since early 2000, manufactured by Kawasaki Heavy Industries & Nippon Sharyo (KNS) under Contract 751B. 21 trainsets of 6 cars each were purchased at S$231 million, and it is the first rolling stock to feature VVVF insulated-gate bipolar transistor traction control system. Kawasaki manufactured 66 cars and Nippon Sharyo manufactured 60 cars respectively with no comparable differences, having been built to agreed specifications. These trains are the third generation of rolling stock to be used on the two lines.

Exterior design
The front of the train spots a more slanted and streamlined look, with the run number display in Orange LED Displays. The C751B train is the first train to have the updated SMRT "Blackbird" livery.

The C751B was also the first MRT train type to feature anti-climbers, which help prevent overriding of the train cab in the event of a collision that could cause a catastrophic failure. They also feature rubber guards to prevent people from falling between cars: this feature was also used on the C151A. However, the rubber guards are now redundant with the introduction of platform screen doors on elevated stations. The C151A, C151B and C151C sets manufactured by Kawasaki Heavy Industries & CRRC Qingdao Sifang are also developed from the Kawasaki–Nippon Sharyo C751B.

Interior design
All cars have been retrofitted with 6 LCD Displays per car and all except trainset 347/348 which features VPIS (Visual Passenger Information System) displays from July 2001 to September 2009. These used to show rail travel information, commercials and movie trailers. The C751B is also the first train to have wheelchair space, with the retrofitting of the elevators in the MRT stations began in 2000. The interior design was also improved; the seats were now 48 cm wide - about 5 cm wider than on previous train types. The STARIS version 2.0 was piloted on train car 3322 in 2010, but it was uninstalled in 2016 as it was not compatible with the updated STARIS displays for C151B and C151C trains.

The LCD Displays were deactivated since July 2007 and LED Displays was not used since January 2008 with the change of voice announcer. All VPIS were removed to make way for the STARIS by 2010. In 2013, support bars are added to the seats with hand grips, and the middle handrails with hand grips are configured to join across nearly one car, as such all triplicates stanchion poles are replaced by regular single grabpoles.

The colour of the seats on each car of these trains are also different from their earlier counterparts - turquoise for M1, cobalt blue for M2 and maroon for DT. All door panels and walls are white, which is a standard appearance of all SMRT trains. Energy efficient lighting was installed on cars 1328 and 3328 in 2017.

Main Propulsion Controller/Motor
The C751B is the second commuter type Electric Multiple Unit (EMU) after the Sanyo 5030 series to feature electric systems fully manufactured by Fuji Electric. Propulsion is controlled by VVVF Inverter with 2-level IGBT semiconductor controller, rated at 415 kVA. Each inverter unit controls two motors on one bogie (1C2M), and one motor car features two of such units. Motors are three-phrase AC induction type, model MLR109, with a maximum output of 140 kW.

Bogies
The C751B uses the monolink axlebox type bolsterless air spring bogie. There are no major technical difference between a trailer and motor car bogie other than additional electrical components for the latter.

Auxiliary Systems
A break from tradition, the C751B features auxiliary inverters for its electrical systems on all six cars of the train. Previously, auxiliary inverters are mounted only on motor cars. The VVVF Inverter is controlled by IGBT semiconductors and rated at 80 kVA. A battery charger is built with the inverter and provides 16 kW output.

Derivatives
The Kawasaki Heavy Industries & Nippon Sharyo C751B forms the basis for the next three rolling stock generations for the North–South and East–West lines, consisting of the C151A, C151B and C151C sets manufactured by Kawasaki Heavy Industries & CRRC Qingdao Sifang.

Operational history
The tender of the C751B trains was called on 12 April 1997 together with the opening of Changi Airport extension and to continuously expand the fleet. The contract was awarded to Japanese firms Kawasaki and Nippon Sharyo on 18 January 1998. The first C751B was delivered in August 1999 to Singapore, before entering revenue service in April 2000. The formal launch ceremony was held on 8 May 2000 at Ang Mo Kio MRT Station.

It was the first train to be painted in the Blackbird SMRT livery since 1998, which was mandated for new and refurbished trains until 2016. These trains were capable of running on both the North–South and East–West Lines at all times. However, they were mostly deployed from 2008 on the North–South Line until 2018 when most trains were moved to East–West Line.

With the opening of the Changi Airport Line, several trains were delivered with luggage racks and were installed in every carriage of the train, taking up the space of two seats next to the door at the end of each carriage. Passengers preferred not to use them in favour of theft and were underutilised as people preferred to hold on to their bags in the train. Luggage racks were eventually removed when the through train service to Changi Airport was converted into a shuttle service, and the luggage rack spaces were replaced by extra standing spaces.

On 13 April 2002, a fault was detected in a C751B train and it was subsequently withdrawn to Changi Depot for investigations. As the train was under warranty, the engineers from the manufacturers of the train and gearbox were flown in on 21 April. They subsequently detected metal fragments in the gearboxes, and those of another 20 trains. On 23 April 2002, SMRT immediately withdrew all 21 C751B trains and suspended the Boon Lay – Changi Airport train through service, replacing it with the Tanah Merah – Changi Airport shuttle service. Train frequencies were also adjusted until 6 May 2002, when 8 trains returned to service. Service resumed on 16 May 2002, with 7 more trains back on service. By end of May 2002, all C751B trains had been returned to service.

Retirement
In December 2019, Toyotron was awarded the contract for disposal of old SMRT trains. On 28 September 2020, the LTA announced that these trains will be replaced by R151 from Bombardier Transportation (Alstom) to progressively replace the 21 C751B trainsets together with the 19 C651 trainsets and the 66 C151 trainsets from 2025 onwards. On 14 March 2021, the first C751B train went for scrap. Currently, as of 6 July 2024, 17 of them are scrapped including all 11 units built by Kawasaki Heavy Industries and only 4 trains remain in service.

These are the trains that are preserved:

Train formation
The configuration of a C751B in revenue service is DT–M1–M2+M2–M1–DT.

The car numbers of the trains range from x311 to x352, where x depends on the carriage type. Individual cars are assigned a 4 digit serial number by the rail operator SMRT Trains. A complete six-car trainset consists of an identical twin set of one driving trailer (DT) and two motor (M) cars permanently coupled together.

For example, set 349/350 consists of carriages 3349, 1349, 2349, 2350, 1350 and 3350 in this order.


 * The first digit identifies the car number, where the trailer cars has a 3, the second and fifth cars has a 1 & the middle cars has a 2.
 * The second digit is always a 3, part of the identification numbers
 * The third digit and fourth digit are the train identification numbers. A full-length train of 6 cars have 2 different identification numbers. For example, 329/330 (normal coupling) or 332/338 (cross coupling).
 * Kawasaki built sets 311/312, 315/316, 319/320, 323/324, 327/328 – 333/334, 343/344, 347/348 and 351/352.
 * Nippon Sharyo co-built sets 313/314, 317/318, 321/322, 325/326, 335/336 – 341/342, 345/346 and 349/350.

As set numbers 301/302 was already being used by a money train (which was a Kawasaki Heavy Industries C151), the C751B trains were numbered starting from 311/312.