william_b_noble wrote:
leave the 4 HP motor in place. Program your VFD to treat it as a 2 HP.
That way, if you want a larger motor, you just reprogram the VFD. If it
came with a 4 HP motor, I'd assume the belts, etc, can carry the HP and not
slip.

It came with a strange pulley system. One small pulley on the spindle
and three larger ones on the motor side and no belt. Minimum RPM
is probably somwhere around 2000. So I have to change the pulley
system in any case.

I've thought about getting a Yaskawa VS Mini J7 inverter. That is a
scalar drive (vector drives a probably too expensive). Would I have
enough of torque at all RPMs if I had a 2-pulley system with ratios
of 1:3 (or 1:2?) and 1:1?

It seems that the J7 cannot handle the 4 hp motor.

Frank