The Magic of Variable Speed Drives By Eric A. Woodroof, Ph.D., CEM, CRM, PCF Buildings Magazine September 2014 DOWNLOAD PDF (it has graphics and equations) Last week I was teaching/introducing the Certified Energy Manager program in Singapore, where the weather is consistently hot and humid, yet they frequently use variable flow HVAC systems. It got me thinking about applications of variable speed drives (VSDs) in data centers and other areas where the cooling load is more