Warco WM16 Mill - Conversion to AC motor with VFD

[Jonathan]

Jonathan, more poles = slower ;)

I know. I've corrected the post and highlighted that in bold. I'd have hoped it would have been obvious from the 4 other correct statements in my post giving the synchronous speed for 4 and 2 pole motors.

2pole @ 50Hz theoretically gives 3000RPM, while 4pole gives 1500rpm.

Only if your theory is no good. Those speeds are the synchronous speeds and if the rotor was spinning at that speed, there would be no current induced upon it and therefore zero torque. For that reason the theory shows the rotor speed will always be below those values, by an amount known as the slip, else the machine is not acting as a motor.