In article ,
"David G. Sizemore" wrote:

Roy Smith wrote:
I don't know much about the NEC, but I do understand polyphase
circuits (4 years of EE in college). I don't think I've ever heard
the term J-factor. What is it?

The "J" factor is the square root of -1. No, really.

We called that "j". Always lower-case, and never with a "-factor" on
the end.

If you have a generator, and you
place 3 "brushes" equidistant around the amature, those 3 "phases" will
be 120deg "out of phase" with each of their neighbors. if you increase
the brushes to four, and place them equidistant, each will be 90deg out
of phase to its neighbor, and 180deg out of phase with its diametric
opposite cousin.

It is interesting that you mention that. It certainly is possible to
build a 4-phase generator. I've never seen or heard of one, but it
would be no big deal to build one. You would really have 4 windings,
not four brushes, but that's a detail.

Now, let's try an experiment. Label the 4 phases A, B, C, and D, in
order. Assume the windings are star-connected, so there's a common
neutral, which we'll label N. Let's further assume that the leg-neutral
voltage of each phase is 120 VAC.

I'm going to give you two panels, each having three terminals on it.
One both panels, the terminals are labeled X, Y, and N. One one panel,
X and Y are connected to phases A and C from our 4-phase generator, and
N is connected to the neutral. On the other, X and Y are connected to
L1 and L2 from a typical center-tapped 240V residential pole drop, and N
is connected to the center tap. On both panels, N is tied to earth at
the panel.

Can you describe a measurement that you can make, which will tell you
which panel is connected to the 4-phase generator and which is connected
to the pole drop? You can use voltmeters, ammeters, power meters, phase
meters, oscilloscopes, or any other tool or instrument you desire.
Assume, however, that both are ideal voltage sources, i.e. you can't
draw enough current from them to significantly load them down.

My claim is that you can't tell the difference.