TRIAL runs with the first of 180 Type HXD1 twin-unit electric locomotives began in April on Chinese Railways' test loop in Beijing. Since then trial running has begun on the Datong – Qinhuangdao heavy haul coal line.

Ordered in 2004 by the Ministry of Railways from a consortium of Siemens and its partner Zhuzhou Electric Locomotive Works, the HXD1 is a derivative of the Eurosprinter design incorporating experience from the 20 locomotives of Type DJ1 delivered to Chinese Railways in 2001.

Intended primarily for the Da-Qin line, the HXD1 is designed to operate in harsh conditions with the 25 kV 50 Hz traction equipment protected from the damaging effects of coal dust.

Technical design was led by Siemens, with many Chinese suppliers involved as part of a wide-ranging technology transfer process. As with other Eurosprinter derivatives, the HXD1 is a modular design intended to permit short assembly times. The bodyshell provides for large components to be lowered directly into the machine room before the roof modules are fitted. Where possible, components are tested before installation.

The standard version of the loco weighs 184 tonnes, but it can be ballasted up to increase the axleload from 23 to 25 tonnes with a consequent increase in tractive effort (Fig 1). If the coefficient of adhesion is at least 0·39, a starting tractive effort of 700 or 760 kN with a 23 or 25 tonne axleload can be transmitted to the rails.

Each half of the twin-unit has an identical control system. This features a train communications network consisting of a wire train bus and a multifunction vehicle bus. These are linked to a central control unit consisting of microprocessor controllers from the Sibas 32 automation system featuring 32-bit processors.

Traction equipment is monitored and managed by four control units, one for each DC link and its connected phase modules. The eight three-phase traction motors have a combined continuous rating of 9?600 kW, and maximum speed is 120 km/h. Regenerative braking is fitted, developing up to 9?600 kW of braking power at the wheel rim. < /p>

• CAPTION: One of the first HXD1 locos hauls a test train on the Da-Qin coal line
• CAPTION: BELOW: Fig 1. When ballasted up to give a 25 tonne axleload, the HXD1 can develop a starting tractive effort of 760 kN