For HVAC pros interested in motors and drives, Tuesday afternoon at this year’s AHR Expo in Atlanta featured a good chance to give the feet a rest and focus on the mind for a while. Air-Conditioning, Heating and Refrigeration Institute (AHRI) presented a three-phase session called VFDs: Method of Laboratory Test and a Case Study.Lab tests may sound mildly interesting at best for some. However, Schneider Electric’s vice president of marketing, Thomas Lowery, served an effective refresher on why variable-frequency drives (VFDs) are worth the effort in the first place and why a certified product matters. Both are meaningful for…