This was my standard advice when I was in the biz:

-If home shop, try as much as possible to keep machinery 1-phase.

-If commercial shop, invest in the phase converter. You might not need any big machines now but you probably will as your business grows. A WB sander, big planer, or large compressor will probably be in your future one way or the other. I can think of several shops in my area who were trying to get by on 1-phase and perpetually complaining about that as a limitation to their growth/capabilities.

As far as a Phase Perfect in the humidity, I doubt that would be an issue. I personally had two customers with PP’s in non-climate controlled shops here in the Austin area and it gets terribly humid at times. The enclosures on those are nema-like. I guess you could put dessicant packs in there if it was a worry but again, I doubt there would be any problems. The biggest concern with humidity will be keeping moisture out of your compressed air system. Good luck with your project.

Erik