Pumping water from bore holes and to reservoirs after purification at Surrey Water's Woodman Stars Pumping Station is carried out using DC motor-driven pumps. A switch to electronically-controlled AC systems has been investigated but the cost of implementing this is considered prohibitive.
This is particularly true while the DC systems are performing the operations effectively.
Helping to achieve efficient pumping operations are a number of motorized, rotary, variable resistors supplied by REO UK. These are used to control the field winding voltage of the DC motor to facilitate speed control. There are also a number of cam-operated micro-switches acting as feed-back speed indicator triggers to permit automated / remote control. The motorized resistors and cam switch arrangement were specially designed to fit into the existing control cabinets without the need for modification to the electrical circuits
Another feature of the REO variable resistors is a manual operation facility which employs a mechanical clutch and hand-wheel fitted to the main drive shaft. This allows for the overriding of automated operations to achieve specific speed running conditions when required.
The REO units are used to control Lawrence Scott DC motors driving Sulzer pumps. Pump motors range in size from a 90/35 bhp (67/26 kW) unit to a 250 bhp (186 kW), at 440VDC and 169 / 66A and 459A respectively.