Ed Smith, Sr., Applications Engineer, HVAC Products Div., Siemens Building Technologies, Inc., Buffalo Grove, IL.

Reducing harmonics from variable frequency HVAC drives

Pulse width modulation (PWM), variable frequency drives (VFDs) are considered the most energy-saving and efficient way to control motors in HVAC, fan, and pump systems. VFDs have proven their worth to facilities and plant managers, supported by bona fide energy savings and performance data. However, the proliferation of drives has exacerbated a problem for some users.