The adjustable flow method changes the flow curve and drastically reduces power requirements.

Variable frequency drives (VFDs) convert constant frequency and voltage input power to an adjustable frequency and voltage source for controlling the speed of alternating current (AC) induction motors. The frequency of the power applied to an AC motor determines the motor speed based on the following equation: Equation 1

VFD main circuit diagramFigure 1. VFD main circuit diagram (Images courtesy of WEG Electric Corp.)
Diagram legend
Pulse width modulated waveformFigure 2. Pulse width modulated waveform
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