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Two phases or not?

J

JW

Jan 1, 1970
0
I'd make a comment here but it is against my new year's resolution.

My New Year's resolution was an easy one this year. Make no New Year's
resolutions ever again.
 
D

David Nebenzahl

Jan 1, 1970
0
Then a Williamson 'Ultra linear' output transformer is four phase?

<http://www.pmillett.com/file_downloads/stancor_ul_schematics.pdf>

See page 4 for a sample schmatic.

I looked at your Stancor PDF. Why in the world would you think I'd think
that transformer is 4-phase???

[btw, the schematics are on pages 2 and 6]

OK, I'll play along here. On page 6 they show an output xfmr with 2
taps. But of course that has nothing whatever to do with phase, as you
damn well know, because the output is referenced to one of the OUTER
LEGS OF THE TRANSFORMER (see that "COM" on the bottom?), so the output
is simply one phase. I was talking about a center-tapped transformer
where the two sides are referenced to THE CENTER TAP.

So again, how does a center-tapped transformer secondary WHERE THE
OUTPUT IS REFERENCED TO THE CENTER TAP (i.e., the center tap is
grounded) NOT generate two separate phases? Please 'splain that.


--
Comment on quaint Usenet customs, from Usenet:

To me, the *plonk...* reminds me of the old man at the public hearing
who stands to make his point, then removes his hearing aid as a sign
that he is not going to hear any rebuttals.
 
W

William Sommerwerck

Jan 1, 1970
0
How does a center-tapped transformer secondary WHERE
THE OUTPUT IS REFERENCED TO THE CENTER TAP
(ie, the center tap is grounded) NOT generate two separate
phases?

After thinking about this, I've come to the conclusion that it doesn't.

"Phase" implies a relative-timing relationship. Simply inverting polarity
doesn't change the timing between the two waveforms.
 
B

Bill K7NOM

Jan 1, 1970
0
William said:
After thinking about this, I've come to the conclusion that it doesn't.

"Phase" implies a relative-timing relationship. Simply inverting polarity
doesn't change the timing between the two waveforms.
If you compare the timing of the positive part of the sine wave you will
see that the two signals have different timing.

Bill K7NOM
 
W

William Sommerwerck

Jan 1, 1970
0
Bill K7NOM said:
William Sommerwerck wrote:
If you compare the timing of the positive part of the sine wave you will
see that the two signals have different timing.

No more than your image in a mirror is a separate being.
 
D

David Nebenzahl

Jan 1, 1970
0
After thinking about this, I've come to the conclusion that it doesn't.

"Phase" implies a relative-timing relationship. Simply inverting polarity
doesn't change the timing between the two waveforms.

That can't be correct.

Let's test the hypothesis. If we had two signals that were 179° out of
phase, would you not say that we had two separate phases? There is a
definite, though small, timing difference.

Let's say the signals were 181° out of phase: two phases again, correct?

So what's "special" or magic about 180° that it wouldn't be considered a
completely separate and distinct phase? Why would phase have a "hole" at
180°? (And for any wisenheimers who will say "well, you must consider 0°
to be a separate phase too!" I say nonsense: that's just a phase
"identity" which we can ignore as being identical to the original phase.)

People seem to be tripped up by the fact that it's trivially easy to
produce the 180° phase, and that it is, as you say, a mirror image of
its respective phase. But this doesn't make it any less of a separate phase.

The other fallacy here is that because we don't actually use 2-phase
electrical power, there cannot be any such thing as 2-phase power. It is
true that two phase power (0° - 180°) is not very useful; that's why we
don't have any 2-phase motors. But technically, a system with two legs
of 0° and 180° is, in fact, a 2-phase system.

Even if it's not called that. Even if it is not used *as a phased
system* (it's used to derive two legs from a step-down transformer in a
120-0-120 arrangement). It's still 2-phase power.

So whaddya say now?


--
Comment on quaint Usenet customs, from Usenet:

To me, the *plonk...* reminds me of the old man at the public hearing
who stands to make his point, then removes his hearing aid as a sign
that he is not going to hear any rebuttals.
 
M

Mark Cross

Jan 1, 1970
0
David said:
That can't be correct.

Let's test the hypothesis. If we had two signals that were 179° out of
phase, would you not say that we had two separate phases? There is a
definite, though small, timing difference.

Let's say the signals were 181° out of phase: two phases again, correct?

So what's "special" or magic about 180° that it wouldn't be considered a
completely separate and distinct phase? Why would phase have a "hole" at
180°? (And for any wisenheimers who will say "well, you must consider 0°
to be a separate phase too!" I say nonsense: that's just a phase
"identity" which we can ignore as being identical to the original phase.)

Repeat the hypothesis a 0º and you will find a hole in there, much the same
as there must be one at 180º.

To understand what is "magical" about that you will need to know phasors and
the math related to that. Once you understand the math that support phasors,
you clearly see why 0º and 180º are the same phasor.

http://en.wikipedia.org/wiki/Phasor
People seem to be tripped up by the fact that it's trivially easy to
produce the 180° phase, and that it is, as you say, a mirror image of
its respective phase. But this doesn't make it any less of a separate
phase.

The other fallacy here is that because we don't actually use 2-phase
electrical power, there cannot be any such thing as 2-phase power. It is
true that two phase power (0° - 180°) is not very useful; that's why we
don't have any 2-phase motors. But technically, a system with two legs
of 0° and 180° is, in fact, a 2-phase system.

Even if it's not called that. Even if it is not used *as a phased
system* (it's used to derive two legs from a step-down transformer in a
120-0-120 arrangement). It's still 2-phase power.

So whaddya say now?

No, it isn't.
 
D

David Nebenzahl

Jan 1, 1970
0
The other fallacy here is that because we don't actually use 2-phase
electrical power, there cannot be any such thing as 2-phase power. It is
true that two phase power (0° - 180°) is not very useful; that's why we
don't have any 2-phase motors. But technically, a system with two legs
of 0° and 180° is, in fact, a 2-phase system.

Actually, there is at least one application which depends on there being
2 phases in ordinary residential power distribution panels: the
so-called Edison circuit. This is where two circuits are run with
separate "hots" and a common neutral, where the neutral conductor is the
same size as the hots.

The only way this can work is if the two circuits are separate phases
(in this case, 180° apart), so that the currents cancel in the common
return conductor.

Apart from this, we wouldn't care if the two legs of the power company's
step-down transformer delivered the same phase of power (just give us
the juice! who cares about the phase?).


--
Comment on quaint Usenet customs, from Usenet:

To me, the *plonk...* reminds me of the old man at the public hearing
who stands to make his point, then removes his hearing aid as a sign
that he is not going to hear any rebuttals.
 
P

Phil Allison

Jan 1, 1970
0
"William Sommerwerck"
"Phase" implies a relative-timing relationship.

** The term " phase shift " generally has that implication - but not the
term " phase " alone.
Simply inverting polarity doesn't change the timing between the two
waveforms.

** Irrelevant - see above.

In any case, for continuous sinewaves a 180 degree phase shift and signal
polarity inversion are completely indistinguishable.



..... Phil
 
D

David Nebenzahl

Jan 1, 1970
0
Repeat the hypothesis a 0º and you will find a hole in there, much the same
as there must be one at 180º.

I don't think so. At 0º, the two waveforms are *identical*, so that's
the degenerate case.
To understand what is "magical" about that you will need to know phasors and
the math related to that. Once you understand the math that support phasors,
you clearly see why 0º and 180º are the same phasor.

http://en.wikipedia.org/wiki/Phasor

Sorry, I don't use Wikipedia as a source of credible information.

But even if 0º and 180º are the same phasor, they're still completely
different waveforms, which is the important thing here, isn't it?


--
Comment on quaint Usenet customs, from Usenet:

To me, the *plonk...* reminds me of the old man at the public hearing
who stands to make his point, then removes his hearing aid as a sign
that he is not going to hear any rebuttals.
 
M

Mark Cross

Jan 1, 1970
0
David said:
I don't think so. At 0º, the two waveforms are *identical*, so that's
the degenerate case.


Sorry, I don't use Wikipedia as a source of credible information.

Open your mind.
But even if 0º and 180º are the same phasor, they're still completely
different waveforms, which is the important thing here, isn't it?

No.
 
B

bud--

Jan 1, 1970
0
So you get 2 phases out of a single phase power transformer?
With 2 separate secondary windings there are 2 phases. Winding A is not
the same as winding B.

With 3 separate secondary windings there are 3 separate phases. Winding
A is not the same as winding B. And winding C is not the same as A. And
C is not the same as B.

With 4 separate secondary windings there are 4 phases. ....

Your transformer supplier can furnish a single core transformer with 4
secondary phases?
Your transformer supplier can furnish a single-core transformer with 2
secondary phases?
Sorry, I don't use Wikipedia as a source of credible information.

Then use your own knowledge of phasors. The representation of a 120/240V
service (relative to N) is +120 and -120, both real. There are no
imaginary components. Plus and minus relationships.
But even if 0º and 180º are the same phasor, they're still completely
different waveforms, which is the important thing here, isn't it?

Completely different waveforms? Plus sine is a completely different
waveform from minus sine. Have you taken trigonometry? On a transformer
secondary the relative relationships are locked at plus or minus. 180
degrees is trivial.

When you are doing calculations on a simple single-phase resistive
system you use phase angles? Most of us use plus and minus signs. With
non-resistive elements phasors are used - see above.

You can, of course, call it whatever you want to. Just expect
communication problems. I remember 2 people here who agree with you. It
is not the only 2 people I would want agreeing with me. Maybe you could
shop around to a different newsgroup - maybe alt.engineering.electrical?


And two-phase does still exist. Some relatively small 3-phase to 3-phase
transformers (like 480/277 to 208/120) connect 2 transformers in a Scott
(T) connection. The transformers are an intermediate 2-phase. That is,
real 2-phase - 90 degrees between the voltages
 
J

Jamie

Jan 1, 1970
0
bud-- said:
So you get 2 phases out of a single phase power transformer?
With 2 separate secondary windings there are 2 phases. Winding A is not
the same as winding B.

With 3 separate secondary windings there are 3 separate phases. Winding
A is not the same as winding B. And winding C is not the same as A. And
C is not the same as B.

With 4 separate secondary windings there are 4 phases. ....

Your transformer supplier can furnish a single core transformer with 4
secondary phases?
Your transformer supplier can furnish a single-core transformer with 2
secondary phases?



Then use your own knowledge of phasors. The representation of a 120/240V
service (relative to N) is +120 and -120, both real. There are no
imaginary components. Plus and minus relationships.



Completely different waveforms? Plus sine is a completely different
waveform from minus sine. Have you taken trigonometry? On a transformer
secondary the relative relationships are locked at plus or minus. 180
degrees is trivial.

When you are doing calculations on a simple single-phase resistive
system you use phase angles? Most of us use plus and minus signs. With
non-resistive elements phasors are used - see above.

You can, of course, call it whatever you want to. Just expect
communication problems. I remember 2 people here who agree with you. It
is not the only 2 people I would want agreeing with me. Maybe you could
shop around to a different newsgroup - maybe alt.engineering.electrical?


And two-phase does still exist. Some relatively small 3-phase to 3-phase
transformers (like 480/277 to 208/120) connect 2 transformers in a Scott
(T) connection. The transformers are an intermediate 2-phase. That is,
real 2-phase - 90 degrees between the voltages
Yes, 2 phase of 90 degree's still exist, so why is that ok but 180
degree's isn't?

Look at power generators (portables), most of them have 2 circuits
from the generator 180 out from each other.. Why is this any different
from a
generator of 90 degrees out ? You can combine a leg of each output from
a those generators also..

It's argument that you won't win from those that truly understand the
meaning of phase angle supplies and the number of supply legs.

Its clear that the maximum you can obtain is only 2 phase angles from
any combination of CT's on a transformer supplied from a single phase
leg how ever, the number of circuits from a transformer can be endless
but not practical, of course.
 
M

Mark Cross

Jan 1, 1970
0
Jamie said:
Yes, 2 phase of 90 degree's still exist, so why is that ok but 180
degree's isn't?

Because the decomposition of two 90º phasor contains an imaginary part.
Without a real part AND an imaginary part, no distinct phases could be
constructed or generated.

There is no imaginary part in the decomposition of two 180º apart vectors,
and, therefore there is no way to construct other phases (phasors).

Sorry, you need to know phasors to understand this principle.
 
J

Jamie

Jan 1, 1970
0
Mark said:
Jamie wrote:




Because the decomposition of two 90º phasor contains an imaginary part.
Without a real part AND an imaginary part, no distinct phases could be
constructed or generated.

There is no imaginary part in the decomposition of two 180º apart vectors,
and, therefore there is no way to construct other phases (phasors).

Sorry, you need to know phasors to understand this principle.

This must be what separates the Electronic and the Fuse puller EE.

I once thought to be an Electrical Engineer or hold an E1 meant, that
you had to know a lot about electricity, evidently you don't. Might be a
good reason why we find it hard to hire some one for a basic electrical
maintenance job that actual understands electrical theory, not many here.

Jamie
 
M

Mark Cross

Jan 1, 1970
0
Jamie said:
that
you had to know a lot about electricity, evidently you don't.

I am not looking for a job, much less in basic electrical maintenace. You
may apply if you feel competent for such simple jobs.
 
J

Jeffrey Angus

Jan 1, 1970
0
Yes, 2 phase of 90 degree's still exist, so why is that ok but 180
degree's isn't?

Because it's STILL a SINGLE phase across the transformer.
Look at power generators (portables), most of them have 2 circuits from
the generator 180 out from each other.. Why is this any different from a
generator of 90 degrees out ? You can combine a leg of each output from
a those generators also..

I serious doubt they make 90 Degree 2-phase generators.

As to combining multiple output windings from a SINGLE phase
generator, the output is STILL single phase.
It's argument that you won't win from those that truly understand the
meaning of phase angle supplies and the number of supply legs.

You're right, _YOU_ won't win that argument.

On combining multiple phases...

On more occasions than I care to recall, I've seen some poor
schmuck buy a 3-5 HP 240 VAC single phase motor, either on a
table saw or an air compressor, and have his "electrician
buddy" give him two of the 120 volt phases of the 3-phase
power in the shop to run his new equipment with.

Aside from the obvious, the voltage is 208 (Not 240), there's
a 120 phase difference between the two leads feeding the motor.
I usually get called in about 2-3 weeks on a "warranty request"
for said motor that just went up in flames.

Jeff
 
P

Phil Allison

Jan 1, 1970
0
"Mark Cross"
To understand what is "magical" about that you will need to know phasors
and
the math related to that. Once you understand the math that support
phasors,
you clearly see why 0º and 180º are the same phasor.

** ABSOLUTE Bollocks.


** Says nothing of the kind whatever.

( Bet the only "phasors" this jerk knows about are the ones used on "Star
Trek")

**** of you pathetic, bloody TROLL 1!



...... Phil
 
D

David Nebenzahl

Jan 1, 1970
0
"Mark Cross"

** ABSOLUTE Bollocks.


** Says nothing of the kind whatever.

( Bet the only "phasors" this jerk knows about are the ones used on "Star
Trek")

**** of you pathetic, bloody TROLL 1!

Phil, I happen to agree with you here, so do you think you could try to
restrain yourself a little bit and not go off the deep end? Tends to
ruin whatever good points you make ...


--
Comment on quaint Usenet customs, from Usenet:

To me, the *plonk...* reminds me of the old man at the public hearing
who stands to make his point, then removes his hearing aid as a sign
that he is not going to hear any rebuttals.
 
P

Phil Allison

Jan 1, 1970
0
"David Nebenzahl"
Phil, I happen to agree with you here, so do you think you could try to
restrain yourself a little bit and not go off the deep end? Tends to ruin
whatever good points you make ...


** Cross has been posting this same sort of brain dead drivel here for
ears - he is totally off with the fairies and beyond all help. There is no
reason whatever to tolerate such vexatious persons.

I see it as a great folly for anyone to do that.

PS:

Usenet is not the real world - usenet is an on-line jungle.

In normal life, I am usually a polite and cheerful person.


...... Phil
 
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