Wire Size Question

[l u k e]

I just got my 30 hp American Rotary Converter in (With digital control) and have spent a few days wrapping my head around the install. I can't quite figure out why American Rotary is suggesting such a large gauge wire to install this unit.

Breaker size was figured using their equation (per their tech dept): "multiply your three-phase amps X 1.732 to equal your single phase amps" that would be 40 amps x 1.732= 70 amp breaker. (No problem)

A.R. suggests 2/0 gauge wire to supply power to the phase converter.

And a #3 gauge wire to supply power to my mill. #3 is not readily available so I'll have to go with #2.

Is it really necessary to use this gauge wire, it seems like over kill.

I’ve been to the NEC web site and can’t seem to locate any useful information.

Any help would sure be great.

[l u k e]

I spoke with 5 electrical contractors (not an exaggeration) and I was advised that #6 wire would do the job.
I guess I was still second guessing everyone, so I called AR and I think I got to the bottom of the issue. (Prior to this all communication was through emails)

At this point I believe the local contractors perhaps were misinformed on what is required with a CNC rated converter.
AR spoke NEC code then gave me unofficial advice on what I could do which makes it a little easier to make a decision on a direction. In all, I think had I just hired someone to install it I probably would have ended up re doing it.