[Jonne]

Yes it's that big servo, or more closely it's
Fanuc spindle motor from Nakamura TMC-4 lathe.
Original system have 12 thyristors to drive that
motor and same time rectify power from spindle
transformer. I don't have spindle controller,
and I don't want either use it. There's some
weird -10 V driving voltages.. I'm using Mach3
and I like to use digital step/dir pulses...

I heard solution something like this:
Normal DC-servo controller which have
added IGBT-transistor bridges with enough
power rating. And of course, I have to put rectifier
on to power line. Any more ideas? Or anyone
accomplish system like this?

[Al_The_Man]

It is probabally a 3 phase motor if it was intended as a spindle motor, not a servo, per se.
10v analogue was normal to drive the spindle controller.
Due to the size, to drive this with IGBT's as is done in a VFD, will require a fairly massive DC supply.
The advantage of SCR control method is it requires no DC power supply.
To use that size on step/dir will probabally involve a S.D. to analogue converter.
Which are available.
Your options other than the original drive might be a suitable size VFD.

Oops ! Just noticed it was DC spindle, in that case I would look for a SCR controller, DC spindles and DC spindle controller's fetch a hefty price.
I imagine the original is 3 phase also, or else this would be the way to go with a sd convertor.
Al.

[Jonne]

Hey, that's good idea! Thanks!