Most industrial motor manuf. offer a line of VFD rated motors with
provision
for mounting a tach or position encoder on the back end of the motor.
One

My CHNC needed encoder feedback on the 7.5 hp 3phase spindle for a VFD with
encoder feedback. I mounted the standard 3phase motor on the mill table,
turned it on reverse from the right angle adaptor in the spindle. bored a
perfect on center hole just a scosh under size of the pin I drove in. Then
mounted a USdigital encoder. Werks Grate.

To run that slow you'd also need to mount a cooling fan because the motor's
fan will run too slow to help.

Karl


Karl