KORAIL celebrated a milestone in Korea's high-speed rail story this April with the 10th anniversary of the launch of the highly-successful Korea Train Express (KTX) network. Since 2004 KTX has carried more than 414 million passengers and today Korail operates 232 KTX services a day carrying around 150,000 passengers.

The high-speed network continues to expand and the Honam Line from Osong to Mokpo is expected to open at the beginning of 2016, substantially reducing journey times in the west of the country.

A new generation of KTX trains will be delivered to Korail for the Honam Line under a contract for 22 trains signed with Hyundai Rotem in 2011. Test operation of the KTX-Honam (pictured) fleet began last November and 15 trains are undergoing testing and commissioning. These trains will be handed over to Korail by the end of this year and a further seven sets will be handed over by the second quarter of next year.KTX

Earlier this year Hyundai Rotem was awarded another contract to supply 15 10-car trains for the new Wongang main line, which is due to open in 2017, linking Wonju southeast of Seoul with the city of Gangneung on the east coast. The trains will enter service in time for the 2018 Winter Olympic Games, which will be held in Pyeongchang.

Suseo High-Speed Railway Corporation has also ordered 10 10-car KTX sets for the extension of the high-speed network to Suseo and Mokpo in 2017. The 57km Suseo high-speed line will link the southeastern part of Seoul with the Kyungbu high-speed line, giving a much larger area of the capital direct access to high-speed services. The line will also serve the new satellite city of Dongtan.

Technical improvements

Alstom transferred the technologies for the original KTX trains to Korean manufacturers through a localisation programme initiated in 1994. At the end of 1996, the Korean government started an independent large-scale research programme to develop a new type of domestically-developed high-speed train. Nearly $US 250m was invested in the project between 1996 and 2002 and this led to the development of just one prototype train, the HSR 350X. Ultimately it took Korea Railway Research Institute and its many academic and research partners 11 years to complete development - six years to design and build the prototype and a further five years for testing and commissioning.

The outcome was the KTX-Sancheon, which was a substantially different train in terms of the technologies it harnessed. The mild steel bodyshell of the trailer cars was changed into a double-skinned aluminium structure. In place of the thyristor-controlled motor block with synchronous ac traction motors used on the HSR 350X, KTX-Sancheon employed IGBT-controlled PWM converters and inverters with asynchronous ac motors.

Rotatable seats were installed, even in standard class accommodation, to provide comfortable seating for all passengers. However, this compromised seating capacity and meant a 10-car train would only seat 363 passengers, compared with 935 on the original 20-car KTX sets. The interior configuration of the Suseo and Wongang trains differs from KTX-Sancheon, and these trains will seat 410 passengers.

Korail is seeking to improve the technology on its high-speed trains and the traction system is a particular focus for development. The conventional propulsion system used on KTX-Sancheon is based on the IGBT-controlled converter and inverter system developed for the HSR 350X prototype, with a single converter and inverter block rotating two 1.1MW asynchronous traction motors (1C2M). This configuration has disadvantages because wheelset maintenance costs are higher due to the need for precise wheel diameter control, and it also limits wheel slip controls in difficult railhead conditions.

It was therefore decided that each converter and inverter block should control only one traction motor (1C1M). Incorporating a new design of 1C1M motor block required major changes to the main circuit and control circuits.

Another major change on the KTX-Wongang sets was the decision to revert to the use of four brake discs per axle on unpowered bogies, a concept that had already been proven on the articulated trailer cars on the first-generation KTX trains. Ventilated discs were used on unpowered bogies on HSR 350X and subsequently on KTX-Sancheon, although these have not proved successful.

The KTX-Honam fleet will be maintained at a purpose-built $US 300m depot at Gwangju in southwest Korea, which is due to be completed next month.

Rolling stock experts in Korea now agree that there is a need to move towards distributed power for future generations of high-speed trains, particularly with the need to increase maximum operating speeds from 300km/h to 320-350km/h. With China already producing high-speed trains capable of operating at up to 380km/h, the Korean rail industry needs to develop trains that are capable of reaching higher speeds in commercial operation.

This process is already well underway with the development of HEMU 430x prototype, which set a Korean rail speed record of 421.4km/h in January 2013. The HEMU 430x will be the basis for a new generation of Korean high-speed trains set to emerge in the near future. Development work has also started this year on a double-deck high-speed train and a high-speed freight train project.

(Visit Hyundai Rotem at InnoTrans in Hall 3.2, stand 101)