I think it has to actually use the commutation signals from the motor to correctly generate the sinusoidal command signals the s series amps require.  I don't really know and am not ready to invest too much time into it.  I've just been seering a lot more big s series than b series amps for sale and figure their might be a cool doodad out there to run them that you have to ask to find out about...like the pico fanuc encoder converter I got for the motor.

Bump

CUI has come out with a programmable BLDC  commutation version that is cheaper than the Pico, the pole count, phase direction and encoder resolution is programmable. The commutation to stator phase relationship is simply done by energizing A & B phase with a DC voltage to orient the rotor, and then the info is stored in flash memory.
The technology is the same as used by Mitotoyo in their digital calipers.
Nosmo

Wow,
This gives me flashbacks, I ran one of those for 4 years!  The Excello is an excellent machine, like Bridgeport, only better built.  The belt speed change is more robust than a Bridgeport too. I pulled the motor off and replaced the belt too. As I recall the motor is bolted to a top cover and you just remove four bolts and lift it off.  I wouldn't toss the variable speed drive, even with a VFD.  There is NO substitute for gearing to get lots of low speed torque.  That little gear motor that drives the speeds up an down in steps set by the setscrews actually works quite well.  You could make it give you just two ranges if you wanted, high and low, and you get to pick what those ranges are.

The table drive is not ball screw.  It has an anti-backlash nut with a spring loaded mechanism to tighten a second nut against the first.  It seems to work okay, but a fair amount of friction so it will never move real fast.

I hope you got the NMTB 40 spindle, because it is way better than the R8.  I would also recommend you put a drive on the knee immediately.  That sucker is heavy, and with a five inch quill travel you WILL spend lots of time cranking that sucker up and down for tool changes!  If you have NMTB start looking for short integrated chucks, and screw machine length drills.  I found a really nice NMTB short chuck, and went to buy more, they had discontinued making them, I got he last one!

Good luck with your project.

Gary H. Lucas