In the early 1990s, British Coal was keen to develop a battery-powered transport vehicle for the transportation of workers underground.  The vehicle was to utilise the latest technology with the aim of matching the performance of existing diesel vehicles, whilst eliminating pollution and reducing maintenance.

At that time, British Coal used switched reluctance DIAMOND® drives manufactured by British Jeffrey Diamond under licence from Nidec SR Drives Ltd . Because of the excellent track record of their drives, British Coal approached BJD to manufacture a prototype vehicle. The project was carried out in conjunction with Ashfordby Colliery, using an SR Drive® motor as prime mover with a nickel sodium battery powering the drive system.

The SR Drive® system was chosen because it is particularly suited to traction applications, providing high torque at standstill and low speeds with a high efficiency over a wide speed range.  The nickel sodium battery was well suited to underground hazardous area application due to no “gassing” occurring when being charged, thus providing more flexibility for the location of charging stations underground. 

A prototype vehicle was produced by British Jeffrey Diamond.  Full regenerative braking was employed with energy recovery back into the battery.  The use of electric braking eliminated the need for dynamic mechanical braking which both reduced maintenance requirements and eliminated a potential source of fire risk.  The vehicle was provided with 4-wheel steering capability, enabling high manoeuvrability in tight underground passages. 

Extensive surface trials at Ashfordby Colliery were undertaken, with the vehicle carrying high payloads over rough terrain and up and down steep gradients. The vehicle outperformed the equivalent diesel vehicle both in hill-climbing and top speed capability.



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