On Wednesday, September 11, 2019 at 10:26:01 PM UTC-4, wrote:
On Wed, 11 Sep 2019 20:54:24 -0400, Clare Snyder
wrote:

On Wed, 11 Sep 2019 16:37:09 -0400, wrote:

On Tue, 10 Sep 2019 17:43:33 -0700 (PDT), trader_4
wrote:

On Tuesday, September 10, 2019 at 8:22:06 PM UTC-4, wrote:
On Tue, 10 Sep 2019 14:01:50 -0400, devnull wrote:

On 9/10/19 1:05 PM, trader_4 wrote:
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.

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

Actually you mean when you hook your scope up in the center of the
single phase winding. I can do the same thing with 2 AA cells and make
it look like the plus end of one battery is actually minus.

Yes, how very unreasonable to hook up a scope using the system neutral,
the system reference point. Is that like an unfair magic trick?
And no, it's not hooking up the scope
backwards. Connect the ground clip to the SYSTEM NEUTRAL. Connect
one probe to L1 you get one sine wave. Connect the other probe to
L2, you get the inverse, 180 phase difference sine wave. Which of
course is exactly what the power source is, two sine wave sources
that are 180 out of phase with each other.

OK so you admit what you see is just an artifact of where you hook up
your scope. If I corner ground a delta using exactly the same
transformer with exactly the same input you won't see anything "180"
out of phase.
In 3 phase it's all 120 degree phase shift. If you connect the scope
across a single phase, of course that is all you will see

But if I ground my scope and look at one of those corner grounded
transformers I will see 120v (RMS) at the center tap and 240v at the
opposite end, in identical phase relationship.

Trader's problem is he can't comprehend that 180 degrees is a straight
line (I guess he had a bent protractor in school) and he starts trying
to confuse the issue with impossible phase shifts.

I'd say your problem is you don't understand the definition of phase
or it's concept. That's obvious in the above statement. A 180 deg
phase difference means you have a periodic waveform that is shifted
half a period with respect to the another periodic waveform of
the same frequency. It's not a straight line anymore than the
90 deg angle in Ralph's old two phase example is a right angle.
In the case of sine waves and similar, 180 phase difference
is the opposite sine wave. In Ralph's example, it's a quarter period
shift.



http://engineering.electrical-equipm...ansformer.html

"As it can be seen from the figure that this type of configurations gives us two phases through the two parts of the secondary coil, and a total of three wires, in which the middle one, the center tapped wire is the neutral one. So this center tapped configuration is also known as a two phase- three wire transformer system."