And just as he begins to understand the three phase wye, we'll throw in a
delta with a wild leg!!



"Beachcomber" wrote in message
...
On Sun, 20 Nov 2005 04:50:31 GMT, "Toller" wrote:


"RBM" rbm2(remove wrote in message
...
When all three lines are used,it is three phase: A-B, B-C, and A-C

So, if I wanted to refer to three phase, where L-N was 120v, I would call
it
208v 3 Phase since a-b, b-c, and a-c are all 208v?


Correct. The voltage naming convention refers to the phase-to-phase
voltage, not the phase-to-ground voltage. If you know the phase to
phase voltage, you may obtain the phase-to-ground voltage by dividing
the phase-to-phase voltage by the square root of 3 (which is 1.73).

208/1.73 = 120
480/1.73 = 277
etc.

In general terms, a three phase circuit is more powerful than a single
phase circuit because it delivers more power from point A to B per
unit of copper conductor and hence, is much more efficient.

AC Single Phase Circuits actually deliver varying sinusoidoil pulses
of power that are a zero 120 times per second (the zero crossings of
the sinusoid).

AC Three phase circuits supplying a balance load such as a motor are
delivering the same level of power continuously, (but rotating in
intensity among the 3 conductors). It is interesting that DC
circuits also deliver power constantly without the zero crossing
breaks.

In practice, 3-phase motors can be cheaper, smaller, quieter, easier
to start, and run cooler and more efficiently for a given HP.