The installation of variable speed drives for fan control in a cooling tower at the Teesside Power Station is reducing downtime as well as giving the potential for improving overall generating efficiency.
Yet one of the initial reasons for the selection of Control Techniques Unidrive SP AC drives for the task was a very down to earth and practical one - they were the only ones that would retrofit into the cubicles previously used for the direct-on-line motor (DOL) starters!
Jon Scott, Senior Electrical and Control Engineer, px limited, the power station's operating company, explains. "We were faced with the need to replace six two-speed motors for one quadrant of the Q501 cooling tower and took the opportunity to consider the options available in view of the maintenance problems we were experiencing due to shock loads on the blades, bearings and gearboxes. When we costed the alternative of variable-speed drives combined with conventional off-the-shelf AC induction motors (at 20% of the price), the bottom line was much the same - but the additional benefits offered by variable speed drives made that proposition much more attractive. The only problem was the narrow dimensions of the existing control cubicles which we wanted to re-use to make the project cost-effective. Only one drives company - Control Techniques - could give us the drives features we wanted in a compact package that would fit."
Depending on load and ambient conditions the water inlet temperature is on average at 30 C and, after cooling, the outlet water is approximately 16.5 C The water flow is 8,000 kg/second (12 Olympic sized swimming pools an hour), requiring a cooling capacity of about 460 MW provided by the 22 fans that supply an airflow of almost 10,500 kg/second (the equivalent of 20,400 domestic fans)..
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