Using Electronic Adjustable Speed Drives for Efficiency Improvement and Cost Reduction

Abstract

U.S. industry and utilities have been using ac adjustable speed drives (ASDs) for more than 50 years. ASDs utilize power electronics technology to control the flow of power to an ac motor, thereby controlling the motor’s speed and rate of energy consumption while modulating process flow through the fan or pump driven by the motor. Industrial ASD applications have typically been those requiring extremely precise speed control, such as in fiber spinning operations with multiple motors. However, controlling process flow by varying the speed in many systems does not require the fast-responding, precise wide speed range regenerative drives frequently needed for “traditional” variable speed applications. Often the required speed range is small and there is limited or no requirement for speed of response and speed control precision. Electronic ASDs have come a long way since their introduction some ten years ago. These drives, which match motor speed to the job with the help of semiconductor devices and switching circuits, have become progressively more efficient and versatile. The cost of electronic ASDs has declined rapidly over the last three years. Pending technology advances promise to make the drives even more attractive in the future, both from a performance as well as a cost standpoint.