On Tue, 7 Aug 2018 10:38:50 -0700 (PDT), trader_4
wrote:

On Tuesday, August 7, 2018 at 11:26:54 AM UTC-4, devnull wrote:
On 08/07/2018 10:55 AM, trader_4 wrote:
Here are the two simple problems that no one on the other side can address
and it isn't because there is any confusion about voltage vs phase.
It's because they are trapped in a obvious unexplainable contradiction.

trader, you keep saying that we get 240v by combining 2 120v phases that
are 180 degrees apart.Â* That's utter nonsense!

It's not utter nonsense. Do you deny that the circuit is two 120v
secondaries that are tied together? How do you draw the simple circuit
diagram, using ideal voltage source that represent what you have there?
I draw it with two 120V voltage sources, with one 180 deg out of phase
with the other with respect to the neutral, or of opposite polarity,
same thing. The IEEE Fellow, power engineer, professor, says exactly
the same thing. If you disagree, show us the circuit model that doesn't use
two 120V voltage sources. And where those sources come from, two halves
of the secondary, or two windings from a generator, or electronically
synthesized from a batter, doesn't matter. In all cases they are 120V
voltage sources and the power into the house looks, acts and is the same.

The nonsense is that they are out of phase with each other. It is one
continuous winding, It is wound in one direction and all of the
current flows in the same direction at any given time. That is one
phase.


The 240v is derived from one continuous secondary winding. You'll note
that the neutral tap is not even used for 240v.Â* And since it is single
phase on the transformer primary, it is single phase on the transformer
secondary.


Sure, you can add a tap long the secondary winding and get a reduced
voltage but it is still single phase.

You get two voltage sources that are 180 deg out of phase or of opposite
polarity with respect to the tap, that's what you get. And the "tap"
is the SYSTEM neutral! It's the reference for your power delivery.
It's not some random, accidental, inconsequential point.

Ready to answer the very simple questions? Fretwell can't, he gets part
way through and then suddenly starts talking about transformers, when
there are no transformers in any of the simple problems.


Problem 1:


Define N phase power?


Problem two:

According to Fretwell, two phase power existed 100 years ago, and it
was over two wires, 90 degrees phase difference. Suppose I run it
over 3 wires instead, with a shared neutral, make it 120V. So,
you have a generator supplying 120V, two coils, one shared neutral.
Would there still be two phases there?
(I believe Fretwell said yes)
Your answer?

So now, I run that from the generator into a house, we have three wires,
120V, two phases.
If I change the phase difference to 179 degrees instead of 90
by rotating one coil, are there still two phases? Yes or no?


Now I rotate it to 180 phase difference. Are there still two phases,
yes or no? If you disagree, explain how it's different, how there
suddenly there are not two phases there.


(My answer is yes and the final step above makes it absolutely IDENTICAL
to what you have coming into the house with 240/120. The electrons
are behaving exactly the same. )


Problem number 3

I take 3 phase power with a neutral into a house. One phase is at zero,
one is at 120, one is at 240, correct? I can see them on a scope, yes?

Now I rotate one coil so that instead of 120, it's at 179. Are there
still three phases?

Now I rotate it one degree more, to 180. Are there still 3 phases,
yes or no?

Now take away the 240 phase. How many phases now? If it's not two,
explain why.

And if it is two, then again, it's now ELECTRICALLY IDENTICAL TO 240/120 service.
IF you believe it's electrically different, explain why and how it matters
in terms of the behavior of the electrons in the service conductors.


Problem number 4:

Draw the basic circuit model of 240/120 service. My model uses TWO
voltage sources, with a shared neutral. One is 120V sin(wt), the
other 120V sin(wt+180) or of alternate polarity connection, if you
like. That is the only way to model that circuit, because that is
what is there. When you center tap it, you now have TWO voltage
sources. Which by the way is exactly what the professor is saying,
you have two sources, 180 out of phase with each other, that's how
you treat it. Do you agree with that? If not, tell us your alternate model.

Problem number 4:

Someone asks why they can't randomly parallel any two receptacles in a house.
My answer is, because you have two 120V voltage sources that are 180 deg
out of phase with each other with respect to the neutral or of alternate polarity if you like.
You can only parallel ones that are of the same phase or polarity.

Your answer?