Variable-frequency drives, or VFDs, are becoming more commonplace in motor retrofits and new installations. And while they boast increased energy efficiency as the main benefit, a small — but by no means insignificant — percentage of the drives are causing major problems in the motor they control.
“A problem with VFDs and motors is a phenomenon called electrical fluting,” explained Nate Morse, technical team leader at AirTight Mechanical Inc., Charlotte, N.C. “This occurs in the bearings of the motor, and, as the bearing begins to fail, it sets up a vibration in the motor. The bearings will eventually fall apart, and that could cause a motor failure.”