On Thursday, August 2, 2018 at 1:08:42 PM UTC-4, wrote:
On Thu, 2 Aug 2018 08:33:38 -0700 (PDT), trader_4
wrote:

On Wednesday, August 1, 2018 at 8:46:09 PM UTC-4, wrote:
On Wed, 1 Aug 2018 12:52:58 -0700 (PDT), trader_4
wrote:

On Wednesday, August 1, 2018 at 2:41:24 PM UTC-4, wrote:
On Wed, 1 Aug 2018 10:49:18 -0700 (PDT), trader_4
wrote:



Explain that to Trader. He seems to think that every time you tap a
secondary you create another phase.

You're completely and deliberately misrepresenting what I've posted here.
You said:

"If the tap was 2/3ds the way along the secondary, would
you say they were now 239 degrees out of phase?"

IDK where that came from, but I replied that if you made that tap,
you'd have one coil with 240 * .66 VOLTS, the other with 240 * .33 VOLTS.
The phases of the two would be exactly the same as with the center tap.
You'd see two phases from the ends of the transformer with respect to
the midpoint.

Exactly except you are simply looking at one phase, looking in 2
directions from an arbitrary point along the winding.

Which creates TWO 120V voltage sources that are 180 deg out of phase
with each other with respect to the neutral.



Do you think the hands on your clock change direction at 12 and 6?
After all, first they are going down, then they are going up.

Do you not understand that 180 deg phase shift is the same as
opposite polarity? If there aren't two phases coming into the house,
why can't I parallel any two receptacles at random? It's just like
with 3 phases. If I want to parallel two, I better be sure they are
the same phase conductor.

Someone comes to you and asks, why can't I just parallel any two
receptacles in the house? What's your answer? And the answer shouldn't
involve transformers, because the answer should apply regardless
of how the service is provided. My answer, there are two different
phases, 180 deg apart, works regardless of how the two phases
got there. Could come directly from a generator as I've cited for
example many times now. Could come purely electronically synthesized
off a battery, could come from an unknown black box, could come from
a center tapped transformer. It doesn't matter, it;s all covered,
all explained, it all looks, acts and behaves exactly the same.
And it doesn't have to be 180, could be 179 deg, 90 deg, etc.
It's all covered. It's the voltages, currents and phase relationships
that define it, not how it was created.

Quite simply you can't connect the ungrounded conductors together
because they are at opposite ends of a 240v single phase secondary.

Could you connect them together if they came out of a black box,
where you didn't know how they were generated? Could you connect
them together if the originated from a generator, with two coils
separated by 180 deg? That's the beauty of consistent definitions.
We define and analyze without having to know exactly how it's
generated, because it doesn't matter.


It certainly matters where they are generated because if they came
from totally separate sources you could connect them together, no
matter how they were polarized and the voltages would either buck or
boost. but there would be no fire. It is the fact that you are using
two halves of a single winding that makes current flow from L1 to L2.

Ridiculous. The behavior of that 240/120 3 wire power service is
defined by the voltages and phase relationships. Same with any power
source. Where it comes form matters not a wit. You have TWO 120V voltage
sources sharing a common neutral, 180 deg out of phase with each other,
or connected in reverse polarity if you like. THAT is what's there.
It;s all you need to know. It could come from a nuclear power plant,
a transformer, or be synthesized electronically. IT doesn't even have
to exist at all, we can analyze it using ideal voltage sources. If
you disagree, give us your circuit model, the professor and I gave
you ours, from elec engineering circuits 101.





Person asks, can I parallel these wires of a three phase system?
My answer: Yes, if they are of the same phase, otherwise no.

Person asks, can I parallel these two receptacles in my house?
My answer: Yes, if they are of the same phase, otherwise no.

In a 3 phase system they are different independent phases so you can
connect them all together (delta)

See, there you go again. Instead of sticking to the example, it's off
to the wilderness. I can explain to a student why you can't parallel
any two outlets, they are 180 deg out of phase. If they were 120V and
in phase, you could parallel them.





The grounded conductor does nor even enter into it at all and there
are not 2 phases at all.


What? The neutral is suddenly gone now? You can't get 120V without
the neutral, except for the special, unusual case where there are loads
on both sides and they are exactly balanced.

Getting 120 has nothing to do with how many phases you have.

In general, that's true.


It is
still the same phase, just cut in half.

It's not just one voltage source when you cut it in half, it's TWO.
And they are tied together 180 deg out of phase, or with opposite
polarity if you like.


If I cut a cookie in half do I have 2 halves of the same cookie or do
I suddenly have two cookies?

Do cookies have polarity and phase?




Again, that's why it's TWO voltage sources coming from the TWO halves
of the transformer and why it looks like, acts like and is two voltage
sources that are 180 out of phase or of alternate polarity, which is
the same thing.

That is where you are just wrong. It is not 2 sources, it is two ends
of one voltage source. Do you understand what a "circuit" means?
It is starting to make sense now, why these professors have to come up
with such convoluted "models" to explain such a simple concept.

I've asked you about 6 times now to give you your basic circuit model
that uses just one source to get 240/120. I've given you mine, the same
as the professor, the same as any first semester EE would. It's TWO
120V voltage sources tied together, sharing the neutral, one 180 deg
out of phase with the other or connected with opposite polarity.

If it;s so simple, where is your model? Where, BTW is your definition
of N phase? How can you be arguing about what something is, when you
can't even define it? And note the definition doesn't rely on transformers,
generators, batteries or anything else.