If they are Getty's/Fanuc they are DC especially if they used the old SCR drives. these motors usually ranged from 90vdc to 180, they were restricted to around 2000rpm max.
what you can do is is to apply a known DC voltage, two auto batteries in series for e.g. and measure the rpm at this voltage, you can then calculate by extrapolation what voltage it would require for 2000rpm or whatever the label rating says.
If you are using PWM drives for example, then you will need to build a suitable DC power supply, If it is not built into the drives.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.