On 9/12/19 7:31 PM, Clare Snyder wrote:

[snip]

Not sure how 4 or 8 phase would even work, electrically as I suspect
half of the phases would duplicate each other - - - - - -

Why should they duplicate each outer? 2 phases don't, the same way 120
and -120 aren't even close to being the same number. Foe them to APPEAR
duplicated, you'd have to be using an inconsistent point of view.

If 8 phases are evenly distributed, they'll be 45 degrees apart.

--
103 days until the winter celebration (Wed, Dec 25, 2019 12:00:00 AM for
1 day).

Mark Lloyd
http://notstupid.us/

"People are zealous for a cause when they are not quite positive that it
is true." [Bertrand Russell]

On Friday, September 13, 2019 at 1:37:55 PM UTC-4, Dean Hoffman wrote:
On 9/13/19 8:37 AM, trader_4 wrote:

A bunch cut.

Simple fact, the example Ralph provided is two phase power. And phase
is not limited to 90 deg, you can make it anything you want, just
rotate the second winding. Of course in physics and engineering, we
don't need to create it physically at all to analyze it, we can do
that on a piece of paper. We take two voltage sources:

120 Sine(wt)
120 Sine (wt+O) where O is 0 to 359

Connect them on a common return, we have three wires, the same thing as
Ralph's example. Set O=180, what you have is another version of Ralph's
two phase power, the same thing as 240/120 into your house, two voltage
sources, 180 deg out of phase with each other.

But isn't there a point where two phase ceases to exist and
becomes single
phase? Wouldn't that be the point where capacitors or a start winding
are needed to start motors? Practically speaking. That's what I was
trying to get around to earlier.

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.






Someone you know really well wrote this at 8:19 am on 9/12.

"There are two phases internally when the cap is in the circuit.
That's why it's there, to give a phase shift.
We call the motor single phase, because they run off a single phase
circuit."

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.

On Friday, September 13, 2019 at 2:17:13 PM UTC-4, Mark Lloyd wrote:
On 9/12/19 7:31 PM, Clare Snyder wrote:

[snip]

Not sure how 4 or 8 phase would even work, electrically as I suspect
half of the phases would duplicate each other - - - - - -

Why should they duplicate each outer? 2 phases don't, the same way 120
and -120 aren't even close to being the same number. Foe them to APPEAR
duplicated, you'd have to be using an inconsistent point of view.

If 8 phases are evenly distributed, they'll be 45 degrees apart.

--


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.

[snip]

You three guys are something else. You all must have had a difficult
time with algebra word problems. Problem 1, one train leaves city A
at noon, headed for City B, traveling at 50 MPH. A second train
leaves City B at 1:30PM, traveling at 70 MPH headed for City A.
The cities are 500 miles apart, where do they meet?

Ralph: That's not a train! The only thing that can be called a train
is one particular implementation of a train. They had a train in Philly
100 years ago, that's the only train allowed. There can't be trains
between those cities.

Cla The trains won't be balanced, they will shake apart

Fretwell: Those are weird speeds. You can't make one train go 50,
the other 70.

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]

--
103 days until the winter celebration (Wed, Dec 25, 2019 12:00:00 AM for
1 day).

"Asking about a time before the beginning of our spherical spacetime is
like asking what lies north of the North Pole. There is no such thing."
Taner Edis, Is Anybody Out There?

[snip]

You three guys are something else. You all must have had a difficult
time with algebra word problems. Problem 1, one train leaves city A
at noon, headed for City B, traveling at 50 MPH. A second train
leaves City B at 1:30PM, traveling at 70 MPH headed for City A.
The cities are 500 miles apart, where do they meet?
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]

--
103 days until the winter celebration (Wed, Dec 25, 2019 12:00:00 AM for
1 day).

Mark Lloyd
http://notstupid.us/

"People are zealous for a cause when they are not quite positive that it
is true." [Bertrand Russell]

On 9/13/19 9:37 AM, trader_4 wrote:
Problem 1, one train leaves city A
at noon, headed for City B, traveling at 50 MPH. A second train
leaves City B at 1:30PM, traveling at 70 MPH headed for City A.
The cities are 500 miles apart, where do they meet?


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

On Friday, September 13, 2019 at 2:35:30 PM UTC-4, Mark Lloyd wrote:
[snip]

You three guys are something else. You all must have had a difficult
time with algebra word problems. Problem 1, one train leaves city A
at noon, headed for City B, traveling at 50 MPH. A second train
leaves City B at 1:30PM, traveling at 70 MPH headed for City A.
The cities are 500 miles apart, where do they meet?
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.


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.

In article ,
says...

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


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.




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.




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