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Traditional slide rule makes energy saving easy

Posted: Monday 27th September 2010

ABB has designed a pocket-size slide rule that shows end-users the savings they can achieve by changing a direct-on-line motor to variable speed drive control.

Using the data on one side, the user first selects the power rating of the direct-on-line motor. A window reveals the typical running costs and kWh if the motor is operated at full speed. As an added twist, the slide rule also equates the energy consumption to the equivalent number of high efficiency light bulbs. By then turning the slide rule over, the user can see the effect of applying a variable speed drive to the application.

Users can quickly compare energy consumption and cost between two applications; the first a motor running at full speed with no damper or throttle, the second a motor being controlled by a variable speed drive with 20 percent speed reduction. By selecting the power rating of the motor, users can compare the cost and KWh usage between the two applications based on running the motor for anything between 8 hours per day over a five day week, up to continual 24 hour usage over a whole year.

For example, selecting a 110 kW motor without any form of speed control consumes 770,880 kWh per year when running for 8,760 hours. This is the same as running 6,111 high efficiency light bulbs. However, if you add a simple variable speed control device to the same motor, the energy consumption falls to 376,189 kWh per year, which is the same as running 2,689 energy saving light bulbs.

“All too often we see campaigns encouraging us to switch off the lights. While I endorse any initiative that saves energy, the impact of installing just one variable speed drive on one 110 kW motor is the same as switching off 3,422 high efficiency light bulbs. How amazing is that!” says Steve Ruddell, ABB’s UK energy spokesperson.

Variable speed drives give businesses the opportunity to run their application in a more efficient manor than traditional control methods based on throttling arrangements, where the motor is driven at full speed and the flow of liquid or gas is regulated by valves, vanes or similar throttling mechanisms. Throttling the output in this way wastes money, whereas reducing the speed of the motor to match the needs of the application allows organisations to save energy and money. Reducing motor speed by 20 percent can save 50 percent of energy costs on a single application, freeing up capital that can be invested back into other areas.

The slide rule is free on request. To order your FREEslide rule, please email your contact and address details to or call 07000 DRIVES (07000 374837) and leave your contact details.

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