Hyundai 18s hit sinumerik 840c

I cant find them where they may be placed on back of motors?

Probably. I guess they feed into the drives but I'm not sure. Do you have schematics for the wiring of the machine?

Yes i will search

Those ones?

So it looks like you are well documented. Nice, that will save you hours trying to follow the wiring around the machine.
I can just barely read it but that is the coolant and hydraulics. On the right are the drives but only the over view. Maybe a bit further you will find the servo motors.

I propably have every book for this machines from part list, to parameters and electric or errors but i have lot of problems with this siemens langue is Czech i use Polish or English i dont have password for plc so i cant change it thats why i consider retrofit i cant afford that long brakes in my workshop actually 2 weeks