If the spindle motor is on a VFD and or the computer and controller run off the 3 phase input you are going to need a CNC rated RPC. A static converter will not work. You can always build one, Or buy one from a reputable builder. Who that is, varies with who you ask. I build my own and for others to fund my hobby machining addiction. So I will not say who to buy it from.
What I will say is that from what you have indicated, you WILL need a RPC that is CNC rated. This means that the leg to leg voltages are all within a few volts at all load levels.