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Koreans start to test 350 km/h KHST

01 Oct 2002

BYLINE: KiWhan Kim

Project ManagerKorea Railroad Research Institute

INTRO: With Phase 1 of the Seoul - Pusan TGV service on course for completion by April 2004, a home-grown 350 km/h Korean High Speed Train prototype is ready to begin reliability trials

PEOPLE IN KOREA really began to pay serious attention to the future potential for high speed travel by rail in the 1990s, when construction began on the 300 km/h line that will eventually link Seoul with Pusan. We now expect this line to be completed around 2010.

Phase 1 of this project, known as KTX (Korea Train eXpress), is scheduled to go into service in April 2004. By this time construction of the new line should be completed between Seoul and Taegu. The remaining 118 km from Taegu to Pusan is being electrified at 25 kV 60Hz so that the fleet of trains based on the French TGV can start to carry passengers throughout this busy corridor.

KTX is expected to change the lifestyle of Korean people, as three-quarters of the population live along the Seoul - Pusan corridor. It is therefore anticipated that demands for the benefits of high speed rail travel will extend to other parts of the country.

The Seoul - Pusan KTX service will be provided by a fleet of 46 trains, each consisting of two power cars enclosing 18 articulated passenger cars. While the first 12 trains have been built by Alstom in France, the remaining 34 are being manufactured in Korea with technical support from Alstom by Rotem, a consortium of suppliers established for this purpose. Korean industries have paid substantial royalties to Alstom for technology transfer and technical support.

To meet the need for high speed trains in Korea beyond the scope of the Seoul - Pusan line, the government and industries have been developing for six years the KHST (Korea High Speed Train). The work has been undertaken by KRRI (Korea Railroad Research Institute) jointly with Kitech (Korea Institute of Industrial Technology), Rotem and related industries. The government has provided financial support.

KHST is designed for a service speed of 350 km/h, and therefore requires more power than the 300 km/h KTX. Like Eurostar, which links London with Paris, KTX has a powered bogie under the outer ends of a set of 18 articulated coaches, giving a total of 12 motored axles.

In addition to this arrangement, the production version of KHST has two passenger cars in the centre of the train that each have one motored bogie, raising the total number of driven axles to 16. The 20 cars are designated P for power (no passengers), M for motored car with passengers, M' for intermediate motored car and T for non-powered trailer car. The planned formation is therefore 1P+1M+7T+1M'+1M'+7T+1M+1P.

Prototype KHST ready

For now, the prototype train that is about to be tried out on the 57 km test section of the KTX line between Chonan and Taejeon has the formation 1P+1M+3T+1M'+1P. The maximum axleload is 17 tonnes, and the tare weight of the seven-car train is 310 tonnes. The front end of the power car has been designed to enhance aerodynamic performance while emphasising traditional Korean beauty.

Trailers that are articulated at both ends are 18700mm between the bogie centres, but the cars with one motored bogie are 21845mm long. The power cars, with their streamlined nose, are 22690mm over the body. The external width of the passenger cars is 2970mm.

Fig 1 shows the arrangement of equipment inside the prototype KHST. Each power car has a single-arm pantograph feeding a transformer that supplies three traction motor control blocks, one for each powered bogie including the one under the adjacent passenger car, and a separate auxiliary power block. However, the intermediate motored car, which would normally be in the centre of a full-length train, has its own transformer, motor block and auxiliary block.

The 1100 kW AC traction motors should be able to propel the prototype KHST at 385 km/h on the test track, permitting the design speed to be exceeded by 10%. The inverter in each motor block uses IGCTs (Integrated Gate Communications Thyristors). It delivers variable-voltage variable-frequency power to the motors using pulse-width modulation. A traction control unit for each motor block regulates the motor current, and determines whether the motor is in power or electric braking mode. The TCU also corrects wheel spin and slide, and protects the motor from overheating.

The motors are supported from the car body and drive the wheelsets through cardan shafts and gears. Coil springs are used for the primary suspension between the bogie frame and axleboxes, and for secondary suspension on the power cars. All of the passenger car bodies are carried on air springs. On the articulation bogies, the air spring supports a cast aluminium ring frame fixed to the body of one adjacent car. The other body is hinged to another ring frame that rotates within the fixed ring frame.

All passenger car bodies are formed from aluminium extrusions, although the power cars are fabricated in steel.

KHST has conventional air brakes acting directly on the wheels of motored bogies and on discs mounted on non-powered wheelsets; there are three discs on each trailing axle. Most of the braking energy in normal service is generated by the traction motors, and either returned to the catenary or dissipated in resistances. It can also be fed to eddy-current brakes fitted to the non-powered axles. Braking is controlled and blended automatically by the brake blending control unit.

In the event of KHST failing in service so that the driver is unable to release the brakes, a brake translator unit interprets the air pressure supplied by a rescue locomotive into the electric commands needed to operate them.

Data handling

To run safely at more than 300 km/h, reliable train control and data handling is very important. On KHST, train control and monitoring is handled through a data network that communicates through a wired train bus. This connects the supervisory control unit (SCU) on each control desk in the two power cars with a vehicle control unit (VCU) on each passenger car. Subsystems on each car are connected to the VCU through a multi-function vehicle bus.

The SCU controls the main functions such as traction, braking, power supply and the speed limit. It also indicates to the driver any malfunction of equipment on the train, and makes a diagnosis of what has gone wrong and what needs to be done to correct the fault. The SCU also transmits data to remote locations through radio links while the train is in service. The VCU controls power distribution on the passenger car along with various systems such as air-conditioning, lighting, public address, toilets and so on.

Automatic Train Control allows KHST to be driven automatically at a pre-set speed, and it also opens and closes the vacuum circuit breaker when the train runs through a neutral section in the catenary.

To guard against a failure of the control system, redundancy is available in the form of hard-wired controls from the SCU governing traction, braking and current collection.

On his control desk in the cab, the driver sees three screens. The one in the centre is driven by the ATC system, and shows the safe speed at which he can drive. The screens on each side display data from the SCU.

Passenger comfort assured

The central part of Korea through which KTX is being constructed is quite mountainous and there are many tunnels. At 350 km/h, passengers would find the sudden pressure changes painful. An active pressurisation system has therefore been installed. This senses pressure variations and uses fans to regulate the rate at which air pressure changes inside the coach.

The bogie developed for KHST has been tested for stable running at speeds up to 400 km/h on the roller rig operated by the China Academy of Railway Sciences in co-operation with Southwest Jiaotong University, using displacement gauges and accelerometers. Lateral displacement did not exceed 1mm, which shows that KHST is stable up to that speed.

The prototype was prepared for test running at Osong depot, which serves the 57 km KXT test track between Chonan and Taejon. The manufacturer's inspection and testing is complete, and around 60 test runs are to be conducted to measure bogie performance, braking, current collection, running resistance and ATC performance. These tests should be completed during October. Starting in November, KHST will undergo reliability tests.

The development of KHST has so far cost more than US$200m over six years. System design, manufacturing and testing have been conducted by KRRI and the consortium team, and the main electrical equipment as well as on-train systems were all developed inside Korea. Successful completion of the prototype train is the result of this co-operative effort. n

CAPTION: Test running has started with the KHST prototype Inset: the cab display is based around three main display screens

CAPTION: Fig 1. Layout of the main power equipment within the KHST prototype

CAPTION: Seating in the first class car is laid out in a 2+1 arrangement, with a mix of face-to-face and airline layouts

CAPTION: Right: An intermediate motor bogie on the test rig in China

CAPTION: Retractable shields reveal the coupler used when a train needs to be hauled by a locomotive

Les coréens sont prêts à essayer le KHST à 350 km/h

En avril 2004, un parc de TGV construits en France et en Corée lancera le service à 300 km/h entre entre Seoul et Pusan, utilisant la ligne existante au sud de Taegu jusqu'à ce qu'une nouvelle ligne soit achevée en 2010. Anticipant la demande de lignes nouvelles ailleurs dans le pays, un prototype maison de Korean High Speed Train conçu pour 350 km/h a été construit et les essais de fiabilité commenceront le mois prochain

Koreas KHST testbereit für 350 km/h

Im April 2004 er