Power Distribution Systems

[Miguel c]

What part of the NEC talks about the old Two phase, 3-wire distribution system (90º shifted) ? I am trying to find it but I have not been able to locate the article. I appreciate your help.

 

[augie47]

The two phase systems are almost obsolete in the US. I believe there were a couple of older cities that still had a very limited use.
The 2 phase system is not discussed much in the NEC but there are references in Art 430 such as Table 430.249.
There is a brief discussion and some references here:

Two-phase electric power - Wikipedia

en.wikipedia.org

 

[zbang]

You'll also find the occasional discussion on the forums here about it, although more often two-phase is 5-wire, not 3. Are you working with an installation of it? A couple of use are curious about places it's still in use.

 

[synchro]

What part of the NEC talks about the old Two phase, 3-wire distribution system (90º shifted) ? I am trying to find it but I have not been able to locate the article.

It is mentioned in 220.61 Feeder or Service Neutral Load.