[thackney]

With a VFD you can do the same job with a smaller motor simply because it doesn't have to be sized for startup loads.

That didn't make any sense to me. And I've sized a lot of motors for process applications.

Pumps develop most of their load under mass flow. Fans develop most of their load as they come up to full speed. A VFD can adjust for same much more accurately in real time.

In a throttling type application, with a varying process, that is quite true. But in steady state applications, the pump/motor are select for 100% run speed and a VFD would only add losses at that point. That is why efficient applications that do vary, and come up to full speed for long times include VFD bypasses.

[Carry_Okie]

That didn't make any sense to me. And I've sized a lot of motors for process applications.

Think mass flow or breaking a thixotropic fluid.

In a throttling type application, with a varying process, that is quite true.

Around here, atmospheric temperatures vary some 50°F daily. That changes delivered fluid viscosities considerably as well as demands on cooling fans. Cycling the fans was not an option for us as viscosity control and therefore temperature control, both in process materials and ambient conditions meant everything to us in terms of material cost in the final product.