You will need a 3 phase motor as well as the VFD.
To do synchronous tapping, you will need a system that syncronizes the Z axis to the spindle encoder.
You may get away with floating tapping, depending how well the control of your spindle is, usually requiring fast accel/decel of the spindle.
Depending again on the VFD, you may require to retain one reduction to go down to low speeds.
If you get a 4 pole motor, you can generally run at 2x base frequency ( 120hz instead of 60hz).
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.