Richard J Kinch wrote:

Mark Lloyd writes:


Both of these (the usual system in homes where the phases are 180
degrees apart, and that other 2-phase system) fit the definition of
"phase".


No, it does not fit the definition. Reversing the polarity does not create
another phase. (Except perhaps in your imagination.)

A transformer reversing polarity does not create multiphase from single
phase.

Multiphase requires a non-zero vector dot product. That's how you get
motors to turn.

You might as well say two legs 0 degrees apart are multiphase, because
there are two of them.

180 degrees out of phase is a different phase, mathematically.

And there's no such thing as the "polarity" of a sine wave.

But you're right in saying that what power distribution folks
mean by multi-phase is not the 180 degree case.

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