VFD 220V 120V & NOISE

[JpBinc]

Hello everyone.

I have a X3 that has been cnc'd since 2006. I am now doing some much needed upgrades. I have mounted a 3 phase 220v motor on the spindle with direct belt drive, to replace the 90vdc spindle motor. The question that I have has to do with the high voltage wiring coming into the mill. I would like your opions on what is the best way to wire it. The pc takes 120v, The drives box (gecko's great drives) is a 120v torrid power supply, and the VFD is 220v single phase in three phase out.(Hitachi SJ200) So my first thought was to just run straight 220v single phase to the inverter and peal 120v off of one leg and run the pc on it. Then use the other 120v leg to run the drives. My concern with this configuration is the noise that the VFD may introduce into the system, and the potential to unbalance the loading on each leg of the 220. The second opion would be to just run the VFD off of a 220v line and then run everything else from a addional 120v line. My concern here, is the fact that I could end up with a grounding problem between the VFD and the reset of the system, and since I will be controlling the spindle from the drives box (Mach 3) a gound potential could be a big problem. I know that the opto isolatators I use will stop this before it becomes tragic, however it still seems dangerous to me. Any advise would be great.

[Al_The_Man]

You only have one source or 240/120 in your building, an additional 120v line originates from the same source, so it does not really matter as long as you run everything in the correct size conductors, and fuse accordingly.
You should run a system ground to the machine and bond everything to this common ground point, the ground should also be run to the VFD and then on to the motor frame, with the 3 ph conductors for the motor twisted together, and preferably run in metallic or metallic liquid seal conduit.
There are many previous posts on this subject.
Al.