When individuals look at a variable-frequency drive (VFD), all many see is a speed control device that is able to either vary the flow that a pump delivers, or establish a regulated pressure for a group of users; this thereby provides comfort to those using the liquids being delivered. VFDs can, however, provide a much higher value to pumping systems, by saving energy and optimizing performance.
One of the primary values that VFDs bring to the centrifugal pump is energy savings. VFDs have a positive load characteristic, see Figure 1. As the speed or flow of the pump goes up, the power consumption of the pump goes from a modest slope to an aggressive one. Slight reductions in speed can make a huge difference in power consumption. This works very nicely with the VFD’s inherent variable-speed capability.