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.
I'd make a comment here but it is against my new year's resolution.
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.
THE OUTPUT IS REFERENCED TO THE CENTER TAP
(ie, the center tap is grounded) NOT generate two separate
phases?
If you compare the timing of the positive part of the sine wave you willWilliam 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.
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.
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.
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.)
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?
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.
"Phase" implies a relative-timing relationship.
Simply inverting polarity doesn't change the timing between the two
waveforms.
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
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.
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?
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?
Yes, 2 phase of 90 degree's still exist, so why is that ok but 180bud-- 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
Jamie said:Yes, 2 phase of 90 degree's still exist, so why is that ok but 180
degree's isn't?
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.
Jamie said:that
you had to know a lot about electricity, evidently you don't.
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.
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.
"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 ...