I'm posting this to try to settle an argument going on in another
newsgroup (alt.home.repair) about phases in electrical power.

Over there, someone posted a question about GFCI breakers that morphed
into a discussion of multiphase electrical power. A disagreement arose
thereafter about whether a center-tapped transformer actually delivers
two separate phases of electricity or not. I'd like to get opinions
here, since at least some folks here have engineering backgrounds: over
there (a.h.r.), not so much. People there tend to be more electrician
types, rather than EEs and such.

The discussion started with a mention of 2-phase power. Turns out that
in the world of electrical power, this has a specific meaning. It refers
to a now-obsolete system of generating power in 2 phases that were 90°
apart, and was used at Niagara Falls:

http://www.3phasepower.org/2phasesystems.htm

And of course there's 3-phase power, widely used today.

The problem is this: several people, myself included, contend that the
two "legs" of power produced by a center-tapped transformer do, in fact,
constitute two separate phases of power, 180° apart. (This is how
household power is delivered in North America, with a step-down xfmr at
the power pole delivering 240 volts in the form of 120-0-120.)

Now it's true that in the electrical industry, this is called
"split-phase" power, and if you tried to tell the guy behind the counter
at the electrical supply house that it's 2-phase, he'd look at you funny.

However, I (and others) say that this is, in fact, true 2-phase power,
even if it's not called that. It just happens to be trivially easy to
generate it from a single phase, as it only involves inversion. (Unlike
3-phase, which requires rotary converters or electronic devices to
generate from single-phase power.)

Take, for example, any push-pull amplifier with a phase inverter or
phase splitter in front of it: it generates two separate phases out of a
single phase.

So, what do y'all say?


--
Comment on quaint Usenet customs, from Usenet:

To me, the *plonk...* reminds me of the old man at the public hearing
who stands to make his point, then removes his hearing aid as a sign
that he is not going to hear any rebuttals.