Both NEMA Premium and IE3 only specify a specific motor efficiency curve to be maintained to reach this efficiency level. Neither discuss the application itself. Submerged motors need to be designed for this purpose and if the manucaturer state NEMA Premium or IE3, this has to be for when the...
Making a pump run faster with a VFD is simple, but as mentioned by several here already, there could be down sides to it. If you run two pumps in parallel and apply VFD to both of them, you would reduce the wear and tear on them for the periods, where you do not need the full capacity.
I always...
