![]() ![]() ![]() One of the most important developments in recent years has been the advancement of variable frequency drive (VFD) technology. Many types of variable speed drives have been used over the years, starting with dc drives used primarily in industrial applications, and mechanical drives that varied sheave diameter. Variable speed drives are also used to control pumps on variable flow pumping systems and to control refrigeration compressors in centrifugal chillers. Variable speed drives are more energy efficient than these other devices (their main advantage), but they also reduce noise generation at part-load, allow fans to operate at much lower loads without causing the fan to operate in surge (an unstable condition that can result in violent pulsations and possibly cause damage to the fan), and reduce wear on mechanical components such as belts and bearings. In HVAC systems, they are used primarily to control fans in variable air volume systems instead of other devices such as inlet vanes and discharge dampers. Variable speed drives (VSDs), also called adjustable speed drives (ASDs), are devices that can vary the speed of a normally fixed speed motor. ![]() Eng., in Fundamentals of HVAC Control Systems, 2008 2.6 Variable Speed Drives The reading text for this course was originally written by. ![]()
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