Ignoramus29895 wrote:

Actually right now, the lathe is on a Phase-A-Matic static phase
converter. The Phase-A-Matic came with the lathe. It runs, but I am
getting only 2 HP out of 3. Maybe I should just leave it as is. I
would not be likely to use all of the HP without coolant.

I want to do the right thing, and it is not immediately obvious what
is the right thing. I know for sure that I do not need to vary input
frequency.

It seems that the phase converter route is nicest to the motor, and
lathe, but is less convenient for me.
I don't know, these just run the motor on single
phase once started,
I think that may also be hard on the motor. Also,
a properly set-up
VFD can give you dynamic braking, which can be
real nice on a lathe
with a big chuck (unless the lathe has a
mechanical clutch-brake
mechanism).

Jon