On Mon, 15 Sep 2008 12:49:06 -0500, "Pete C."
wrote:


Karl Townsend wrote:

Sounds like you need to run a much lower pitch prop. If it is cavitating,
you are just wasting energy. Are you running it in a tunnel? Pitch?
Diameter?

I need to run lower RPM to get rid of the cavitation. I'll need a higher
pitch to still move enough water. My question is do I need a larger motor
and VFD.

Karl

I might start with the VFD. If it's cavitating I'd expect it's being
driven too fast, and slowing it down to stop the cavitation may still
give you the same flow since the cavitation isn't helping the flow.

Indeed.

Ive had the same issues with 3ph fans..run them too fast and they
simply stop pushing air, so had to throttle them back to a lower speed
and voila! they started pushing air again.


"Obama, raises taxes and kills babies. Sarah Palin - raises babies
and kills taxes." Pyotr Flipivich