VFD Energy Saving

Centrifugal pumps, in particular, are often oversized to ensure they will always meet performance requirements (or to allow for performance degradation in corrosive applications, or just a stack-up of engineers' safety margins). The pump is then throttled back with a control valve to achieve the desired flow. This can be very inefficient, as the pump will be generating much more head than is really required for the process or application, and therefore absorbed power is higher than is really necessary. Using VFDs, pumps can be sized to operate as close as possible to the Best Efficiency Point, which itself saves energy, but the flowrate can also be controlled without generating unnecessary excess head. In a large process plant running 24/7 energy savings can be quite substantial.

See this thread for more detail about how VFD saves energy: http://cr4.globalspec.com/thread/55271 (especially the comment # 4).

- MS