Drax Power Ltd, located near Selby in North Yorkshire, operates the largest coal-fired power station in the UK.  At full power it burns 36,000 tonnes of coal per day, resulting in around 7,000 tonnes of ash.  The process of disposing of this by-product starts beneath each furnace, where high-pressure water jets sluice away the ash, passing it through crushers, which reduce the particles to a size suitable for water transportation.  High-pressure motive water is then used to carry the ash slurry to concrete settling pits, where the water is allowed to drain away.  The ash is finally lifted into trucks by grab cranes for re-use in products for the construction industry.

SR Drives Manufacturing Ltd has supplied a 75kW variable speed SR Drive^® system for one of the ash grab cranes, replacing the aging slip-ring induction motor on the winch

drive system.  The brushless SR Drive^® motor provides the high torque at slow winding speeds required to raise and lower loads of up to 3.5 tonnes.

The precise torque control provided by the matched SR Drive^® motor and power converter allows the operator to raise, lower or hold the load using motor torque only. This substantially reduces mechanical braking and virtually eliminates maintenance of the braking system.

The superior thermal management of the SR Drive^® motor allows the use of convection cooling without the need for a fan, despite the motor’s confined position on the crane.  Also, the motor’s ruggedness and simplicity has provided Drax with improved reliability in an area where access for maintenance is difficult and expensive.