Two phases or not?

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

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

On 1/28/2011 6:38 AM William Sommerwerck spake thus:

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.

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.

No, it isn't.

--
Mark Cross
If Linux doesn't have the solution, you have the wrong problem.

On 1/28/2011 11:19 AM David Nebenzahl spake thus:

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.

"William Sommerwerck"

** The term " phase shift " generally has that implication - but not the term " phase " alone. ** Irrelevant - see above.

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

.... Phil

On 1/28/2011 11:28 AM Mark Cross spake thus:

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?

--
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.

Open your mind.

No.

--
Mark Cross
If Linux doesn't have the solution, you have the wrong problem.

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

--
bud--

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.

This, from an illiterate ham radio junkie?

--
You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.

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.

--
Mark Cross
If Linux doesn't have the solution, you have the wrong problem.

Actually, you can't find enough idiots willing to kiss your stupid ass.

--
You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.

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

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

--
Mark Cross
If Linux doesn't have the solution, you have the wrong problem.

"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")

Fuck of you pathetic, bloody TROLL 1!

..... Phil

On 1/29/2011 5:35 PM Phil Allison spake thus:

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.

"David Nebenzahl"

** 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

Yes, Phil is correct in his insertion how ever, you can't teach a lot to fuse pullers, I don't know why Phil even tries.

Jamie