So long-story-short preface: I got a(nother) new job, and today I saw something that I have a question about.
It was theater lighting, and the individual wires for the lights had black, white, and green sheathing. The cable sheathing itself was labeled “12/3.”
To me, 12/3 usually means 12/3 WG, black/red/white/green. I would have called it 12/2 with ground. So my curiosity asked the guy I was working with (not an electrician, but a lighting designer) and he said well, it might be different because it’s 3-phase. 3-phase, said I? Why is it 3-phase? But I guess what I saw makes sense, because in that case there would be 3 live conductors, but then I was thrown off again because one was green, which is as far as I know generally understood to be a ground.
I can possibly have my next questions answered tomorrow if I can track down the right person for probably way longer than they have to spare, but I know we have both theater people and electrical experts here, so:
1- If it actually is 3-phase power, why do lights (power-hungry, large, and many; granted, but in a small auditorium) need 3-phase power?
1.5- If it is 3-phase, wouldn’t the 3rd conductor be colored something beside green? Red, for example? Or is that standard?
2- Could it be single phase power pulled off of a 3 phase supply?
3- Why do theaters use 3-phase power? I have a basic understanding, so I think that maybe it is just better for a power-hungry lighting setup. I was working in a high school theater, though, so I wouldn’t think it would be that much of an issue. My theory based on that is that the fixtures themselves are standardized to be used in much larger venues where 3-phase would be necessary; so even smaller spaces install 3-phase in order to use the same fixtures since they are more readily available.
Just downloading some thoughts on notes I took today, now pardon me while I go Google some more shit
Thanks!