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The UK’s first hydrodynamic screw generator, modelled on the ancient ’Archimedes Screw’, is providing power for the River Dart Country Park near Ashburton in Devon.

At the heart of the installation, designed and installed by GP Electronics, is a control and regeneration system comprising two variable speed AC drives from Control Techniques.

About 1.5 tonnes of water flows through the device to turn it at an average of 30rpm, driving a 75kVA generator (with a substantial disk brake) via a 30:1 gearbox and belt drive.

The first of the 55kW Unidrive SP AC drives controls the speed of the system, constantly in braking mode, to maintain the 4.5m head of water within +/-5mm at all times.

Because it is a positive displacement machine, the slower the screw is allowed to run, the less water runs through and the head is maintained.

This means that the level of water throughout the screw is at the centre level, experience showing that this gives the best efficiency.

A level meter (head sensor) sends a signal to the controlling computer, which then determines the required drive speed.

The second drive, in regenerative mode, produces clean power to the park’s power system, providing electricity for Holne Park House, offices, caravan-park, kitchens and cafe.

Any excess power, over and above that required, is fed back to the main electricity supply grid.

A Unidrive SP ’solutions platform’ AC variable speed drive range spans 0.75kW to 1.9MW.

It is configurable into five operating modes – open- and closed-loop, vector, servo and regenerating.

With a range of plug-in module options, its on-board PLC can be supplemented with programmable and specialist feedback and communication modules.

Control Techniques

Control Techniques, an Emerson Industrial Automation company, is a world leader in the design, production and marketing of electronic variable speed drives for the control of electric motors. Our strategy is to concentrate on delivering drives and servo products that enhance the productivity of our customers’ machines and processes.

We operate through a global network of drive and application centres that both distribute product and add value by building our drive products into custom designed systems and by offering the highest levels of customer service.

Our Control Techniques drive centres also provide us with invaluable feedback and market intelligence so that we can further improve our products and service. This customer focused strategy will enable us to continue to grow profitably.

Our competitive edge is based on our unique focus on drives, our strength in research and development, our investment low-cost manufacturing and an effective worldwide marketing strategy.

Emerson Industrial Automation, a business of Emerson, is a global technology provider that enables productivity, efficiency and quality gains for customers across a spectrum of industries. Our products include alternators, electric motors and drives, electrical distribution devices and mechanical power transmission, fluid automation and ultrasonic joining solutions. Visit our website for more details.

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