Karl Townsend wrote:
A large induction motor excited with DC can produce plenty of drag
torque. It doesn't take much DC, either, because the "slip" speed is
1750 RPM rather than the few RPM it sees as an induction motor.
It'll get hot fairly quickly, though. You could adjust the drag
torque by adjusting the DC excitation to the drag motor; all you'd
need would be a bridge rectifier and a Variac.


Ideally, I'd like to run it an hour. My pump can run 24hrs a day if its dry,
I want to make sure nothing in the drive is stressed as much as possible.
That's why I went so oversize. My thinking is that if it will run an hour,
it should run a month.

I do have a 540 rpm PTO irrigation pump that could be connected to a three
phase motor. Any reason that testing at or near 540 RPM wouldn't be valid
for results at 3600 RPM (submersible well pump RPM).
Running a 30 Hp 3450 RPM motor at 540 RPM will give 4.5 HP! The torque
output stays constant at the lower speed, so you get 15% of rated output.

Jon