three Romex sets in ceiling box

[trader_4]

No, because phase is simply the relationship of one periodic waveform to another. If you look at the two waveforms on a scope, with Ralph's example of two phases on three wires, you'd see two sine waves offset by 90 degrees, one quarter of a period. If you rotate the winding by ten degrees, you'd see it shifted by 100 degrees. If you rotate it to 180 degrees, you see it shifted by 180 degrees, one the opposite of the other. How practical any of them are to do anything in particular, what we would or could use them for, is a separate issue. Theoretically you could start and run a motor with any phase difference other than 180, but that doesn't mean that the 180 phase shift isn't there, isn't real, just because it can't start a motor.

And there are no contradictions there. If you look inside the motor, look at the voltage waveforms, you'll see two sine waves, one shifted in phase with the other. Take a look at the three wires in your 240/120V service, connect the scope probe to the neutral which is the system reference point and you'll see two 120V sine wave voltage sources, one 180 deg out of phase with the other. It's the same thing, only

180 deg, instead of 90 or whatever.

I'm the only one here who can give a definition of N phase power:

Power delivered from N voltage sources that are of the same frequency, differing in phase.

Sine(wt) one phase

Sine(wt) Sine(wt+O) two phase

Sine (wt) Sine (wt+O) Sine (wt+P) three phase

That covers Ralph's two phase (O=90), three phase (O=120,P=240),

240/120V (O=180)into your house, on up to N phases. That's the beauty, it's consistent, uniform, I'm not stuck with but it was 90 deg in Philly, those phase shifts are weird, it's not mechanically balanced, IDK what happens.... That center tapped transformer is two 120V voltage sources 180 deg out of phase with each other. That's the only way 240/120 works.

[trader_4]

I agree. It's another example of how you wind up wandering in the wilderness when you don't approach things logically, methodically and consistently.

We can have as many phases as we want and they can be at whatever phase angle we choose.

[hah]

[snip]

The actual speed of train B is the speed of train A multiplied by the fifth root of the difference in the departure times (given in seconds) and divided by pi.

[snip]

[Mark Lloyd]

[snip]

I always liked word problems (and have no problem with 100-degree phase angles).

There were always some kids in school who hated word problems. Maybe arithmetic was hard enough without having to think too.

[snip]

[Jethro Bodine]

Trains are never on schedule so the best guess would be they meet at the scene of the accident.

[trader_4]

But in the beginning, word problems really throw you a curve, at least they did for me. You understand equations, solving them, but then when you have to come up with the actual equations for something like the train example, when you're first exposed to it, it's like starting all over. The only similar experience was probability and statistics, which is worse. It's deja vu all over again. You know the various formulas for probablility too, but trying to figure out which ones to use, how to approach a problem, that's another thing.

Another thought came to mind with the center-tapped transformer issue. Those that say it's just one transformer, one source, have they considered what happens when there is a load with reactance on one side of that secondary, different from the load on the other side? Then the voltage and current waveforms are not necessairly going to be zero and 180. You could have a phase difference, say 175 deg phase difference instead of 180 between the voltages or currents one either side with respect to the other. Treating them as two 120V voltage sources allows for that. And that kind of analysis was the point of the paper by the professor.

[Ralph Mowery]

I had all A's in high school math. However those train problems always seem to throw me for some reason. Most other word problems were relative easy.

English and history were just barely passed, science and math were easy. I hated the stories we had to read, but could diagram almost any sentence with no problem. History had too many names and dates for me to remember. I am more of a thinker than one that has a good memory. I also seemed to have a big problem remembering the formular to convert deg F to deg C. Very easy to work out, but I seemed to always add or devide when I should subtract or multiply.