Liu YoumeiMember of the Chinese Academy of Engineering, Zhuzhou Electric Locomotive Works, Ministry of Railways
ON JUNE 24 1998 Chinese Railways tested a modified Shaoshan 8 electric locomotive hauling five coaches on the Beijing - Zhengzhou main line, setting a national speed record of 240 km/h. Together with a related series of high speed test runs, this laid the foundations for the development of a 200 km/h EMU.
Such a vehicle is considered essential for inter-city service on high-density corridors in a market economy where competition from cars on newly-built motorways will soon be a fact of life.
CR began developing a high speed EMU as part of the ninth national five-year plan. Research and development for the DDJ1 Bo-Bo power car was entrusted to Zhuzhou Electric Locomotive Research Institute and Zhuzhou Electric Locomotive Works; the prototype vehicle was completed at the end of May 1999. Since then the power car has been married in a push-pull formation with six trailer cars built at by CR's passenger rolling stock factories in Changchun, Sifang, Tangshan and Puzhen for a programme of trials.
There are four types of trailer. One is a driving trailer with second class seating, and one is a double-deck car, also with second class seating; the others are both single deck, one having first class accommodation. There are 438 seats in total.
Normally the train will not exceed 200 km/h, but the design speed is 220 km/h. This requirement is reflected in the fine aerodynamic shape of the nose and the domed feature of the roof. Bogies with good dynamic performance and low unsprung mass have been developed so that forces exerted on the rails are kept as low as possible.
Lightweight construction techniques have been used for the bodyshell, the bogies, the main transformer and other components, allowing the all-up weight of the power car to be kept to 84 tonnes. This was the first time that a 21 tonne axleload had been achieved on a four-axle traction unit in China, and we anticipate that it will give good performance at high speed.
Also unique in China is the power car's continuous rating of 1000 kW per axle. Power is taken at 25 kV 50Hz. The secondary windings of the main transformer feed an asymmetric three-phase bridge, which is controlled to produce a constant current DC output for traction. Stepless variation of the excitation current means that any desired speed set by the driver can be maintained automatically. Constant power output is delivered by the motors across the range 127 to 200 km/h.
Neutral sections are detected automatically, shutting off power and reapplying it once the neutral section has been passed without intervention by the driver.
Microprocessors are used in the control circuits for traction and braking, over-speed protection, anti-slip and wheelslide protection, blending of dynamic and pneumatic braking and a range of other functions including fault diagnosis. Supplementary rheostatic braking is provided, giving braking power at the wheel rim of 2800 kW. This is blended with the DK-IB electro-pneumatic braking, which is controlled from an integrated circuit board.
Automatic train protection takes the form of a LKJ-93 speed monitoring and recording system for use on routes fitted with the relevant wayside equipment.
Auxiliaries are fed from an AC-DC-AC converter, and there is a 600V DC supply to the train line for hotel power, including air-conditioning.
The EMU has run on the Guangzhou-Shenzhen route for verification trials. In the future series-built versions will run on routes linking Beijing with Tianjing, Shijiazhuang, Qinhuangdao, Shenyang, Harbin and Dalian, and on other electrified inter-city routes.
In the future CR plans to develop a 200 km/h locomotive with AC traction motors and a power car with a continuous rating of 1200 kW on each axle. This will take Chinese electric traction technology to an even higher level.
TABLE: Table I. Main data for Chinese Railways DDJ1 EMU power car
Gauge mm 1435
Maximum speed km/h 220
Power supply 25 kV 50Hz
Mass tonnes 84
Wheel diameter, new mm 1250
Continuous rating kW 4000
Starting tractive effort kN 180
Continuous tractive effort kN 110
Overall length mm 18316
Overall width mm 3100
Distance between bogie centres mm 9400
Bogie wheelbase mm 2900
CAPTION: Fig 1. Equipment is arranged centrally in the power car body
CAPTION: 1. Cab 6. Braking resistors 11. Capacitor cubicle
2. Kit cubicle 7. Electrical apparatus 12. Pneumatic braking
3. Auxiliary converter 8. Compressor 13. Signal & ATP cubicle
4. Main rectifier 9. Air dryer 14. Traction motor blower
5. Main transformer 10. Train line module 15. Microprocessor control cubicle
CAPTION: Fig 2. Starting tractive effort from 0 to 5 km/h is 180 kN; the unit can maintain a continuous tractive effort of 110 kN