three Romex sets in ceiling box

Sure, what you copied and pasted was what one implementation of two phase power looked like a hundred years ago. No one denies that existed. Are you insisting that any two phase power system has to be 90 deg because that happened to be one of the many possibilities that was actually implemented?. What you have is just an example of *one* implementation of a two phase power source. It's not a "definition" of anything. Which of course is why you can't answer the simple questions posed, eg if the phase angle difference was instead set to 89 degrees, 130 deg, 175 deg, would there still be two phases there? If not, why not? I guess you're implying the answer is no, it has to be 90 deg and only 90 degrees is ever possible? What happens if I rotate one coil by ten degrees? It all collapses into a black hole or something?

Those that understand can answer simple questions, like those I posed.

Oh my, while describing 240/120V service, Clare just said the voltage of the "TWO PHASES" coming from the transformer are additive. Bingo!

Missed this earlier. First you say that each neighborhood gets one of the three phases, then you say the typical transformer is connected between TWO phases, which would be impossible if there is only one phase going to a neighborhood. The first part is what I see here mostly, except it's not each neighborhood it's one transformer is connected to one of the primary phases and it serves a few houses. The next transformer is connected to typically a different primary phase, etc.

You have Delta distribution but Wye is very popular.

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Medium voltage is typically single phase when it hits the distribution transformer, either as single ended wye distribution (one hot and one neutral) or delta distribution (2 hots) but that is still single phase if the 3d phase is not present on the hubs. The output of the transformer is also single phase that gets divided with a center tap. That is how professionals describe it, no matter what contortions people go through to explain it to morons.

Exactly!

I have a Siemens breaker panel and a Generac ATS, both labeled single phase.  Only a moron would claim it's 2-phase.

My neighborhood in Maryland had delta distribution with 2 phases feeding each transformer. I screwed with them, about red leg three phase but they would not put that in a 1&2 family. It would have only cost them one more transformer but no dice.

Not this professional, who I've cited before. An IEEE fellow, professor of electrical engineering, power industry consultant, presenting a paper at a power engineering conference:

Distribution engineers have treated the standard ldquosingle-phaserdquo distribution transformer connection as single phase because, from the primary side of the transformer, these connections are single phase and, in the case of standard rural distribution, single phase line to ground. However, with the advent of detailed circuit modeling, we are beginning to see distribution modeling and analysis being accomplished past the transformer to the secondary, which now brings into focus the reality that standard 120-/240-V secondary systems are not single-phase line-to-ground systems, but they are three-wire systems with two phases and one ground wire. Furthermore, the standard 120-/240-V secondary system is different from the two-phase primary system in that the secondary phases are separated by 180deg instead of three phases separated by 120deg"

And then he proceeds to analyze the circuit back to the transformer, treating it as two voltage sources that are 180 deg out of phase, applying basic electrical engineering principles. Exactly what I've said. And you have to treat it that way, there is no other way to correctly analyze it, which is the point of the paper.

I'm sure he could and would answer the simple questions I posed too, about changing the phase of Ralph's old 90 deg two phase power to 79 deg,

Sine(wt) Sine(wt+ O)

O = 90 deg, you have Ralph's example O = 180 deg, you have split-phase O = 360 deg, you have two sources in perfect sync

In your world, for some unknown reason, when O=180, we must fall into some mysterious black hole, where the same rules that apply everywhere else, no longer apply. In my experience, science and engineering does not work that way.

Primary doesn't have a neutral.

Of course it does in a wye configuration. Did you look at all those pictures of pole transformers I posted links to? One connection on top of the transformer to one primary phase,, the other side is connected to the neutral, you can see the neutral in some of those pics.

I am talking about people in the trade, not some professor who has never touched a piece of wire. Terms have meanings. When you have to blur the nomenclature to get novices to understand you corrupt the meaning of the term.

Again we are talking about the meaning of terms. "Primaries" refers to the "ungrounded" conductors feeding the input of a transformer. The NFPA is really trying to get away from the term "Neutral" because it gets misused so often and they prefer "Grounded Conductor". You notice that replacing neutral more in every cycle.

In other words, you can't handle the most basic electrical engineering principles that show electrically what that service is. It's like denying that tissues are actually a soft paper product made from trees and insisting that they are just Kleenex, that's all they are, that's all they ever can be, because that's how they are commonly referred to.

The ubiquitous AA alkaline battery is two phase as well. If you check the battery voltage, you'll have +1.5 volts. If you reverse the leads on a voltmeter, you'll have a negative -1.5 volt phase.

Every electrical manufacturer in the US calls it single phase.

You and some nutty professor call it two phase.

You might want to rethink your strategy.

Phase only applies to sources with periodic waveforms. What you're talking about with a DC source is polarity.

You might want to improve your reading comprehension skills. Neither I nor the professor said that we would call it two phase. Only that what is actual there are two voltage sources, two phases that are 180 deg out of phase with each other. Again, your silly argument is like saying that because tissues are called Kleenex, that someone who analyzes them, correctly applies science and says they are a soft paper product made from trees, is wrong.

How would you draw a Thevenin equivalent circuit that represents the transformer delivering power to a house?

No, a battery is just a square wave two phase.

You only *appear* to have two phases when you hook one pair of your oscilloscope leads up backwards.