On Mon, 15 Sep 2008 09:00:13 -0500, "Karl Townsend"
wrote:

My apple water bin dump uses a .5 horse 3 phase 220 VAC motor attached by
pulleys and belt to an outboard motor prop in a tube to pump water. Maybe 1"
head at 100+ GPM. I just measured the current draw on this motor at 1.5 amp,
2.0 amp, and 2.2 amp with a clamp A-meter.

Its a 1725 RPM motor with 2.2 reduction to the prop, so the prop turns about
800. Its a NOISY operation. The prop cavitates and pulls air even with all
the deflectors I can install to stop the vortex. (I've only lived with it
since 1988)

I bought a prop that will throw a guestimated 3 times the water per
revolution. There's no way to know until its installed. I have the physical
room to change the pulleys and get a 3.5 reduction or about 500 RPM. That's
most likely too fast and too much water.

OK, now to the question. Will installing a VFD and running the motor at 50%
speed have a good chance at working? Or, do I need a larger motor and VFD?
I want to move the same amount of water.

Call amusement ride builders like Arrow Dynamics, S&S or Vekoma, or
your local amusement parks that have these ride systems - does the
Mall Of America have a log flume or 'Tunnel Of Love' style dark rides?

The standard propulsion method for the boats in a flume ride is a
small propeller in a cast aluminum or bronze vortex cone, direct
coupled to a submersible well pump motor. Four stand-offs between the
vortex base and the mounting bolts on the shaft end of the pump,
debris screen optional. Creates a nice current, and motor cooling is
never an issue.

And they do make inverter duty submersible well motors.

-- Bruce --