Why is residential wiring known as single phase?

[rbalex]

So you can't support your position with a solid reference? I didn't think so.

It is unprofessional to respond with condescending remarks.

That indicates that you know you are wrong.

At least four engineers, with decades of experience think you are wrong.

Problem is that some members may actually believe your claims.

It is simply ludicrous to claim that the phase constant is not really the phase constant but is something else.

You finally gave in on the polarity/in phase issue. Why should anyone believe anything else you say?

No reference, no credibility!

Am I to believe that, as far as you are concerned, the standard of reality is YOUR education and what YOU understand or comprehend? It is beginning to sound like that since you keep bringing YOUR personal history as the conclusive evidence for everything.

I'm not particularly worried about my credibility with the rest of the Tribe either; I don't have a Myth to protect. Then again, I haven't seen those with the math competence rushing to your aid recently. What you, they and I have agreed on is a definition of "in phase." That doesn't erase that every valid voltage function can be written with the ?same phase.? See Bes' Post 1583 He bolded can. He hasn't responded to 1585 yet.

 

[rattus]

No reference, no cred!

 

[rbalex]

No reference, no cred!

Since you cannot or will not make the cognitive leap that identities work beyond your experience, then regretfully, I must put you back in the ?Ignore with a clear conscience? corner for your lack of competence to even discuss the issue, let alone argue it. Besides, you've broken the rules with enough false assertions.

This doesn't mean I believe you lack the intelligence; just the competence. You seem to have inoculated yourself from the ability to transfer a valid math concept from one application to one you haven't seen before.

 

[rattus]

Since you cannot or will not make the cognitive leap that identities work beyond your experience, then regretfully, I must put you back in the ?Ignore with a clear conscience? corner for your lack of competence to even discuss the issue, let alone argue it. Besides, you've broken the rules with enough false assertions.

This doesn't mean I believe you lack the intelligence; just the competence. You seem to have inoculated yourself from the ability to transfer a valid math concept from one application to one you haven't seen before.

For a person who insisted on definitions, standards, documents, etc. You seem very reluctant to do the same.

You speak with forked tongue.

Where is the reference??

No reference, no cred!

 

[gar]

120301-1505 EST

rbalex:

I will respond to you sometime later. I really do not know the basis of your argument. That I am trying to figure out.


Rick Christopherson:

Your comment about noise has no bearing on the discussion. The discussion is based on a sine wave signal, meaning a sine wave shape and only one frequency. Further by assumption the signal is steady state and ideally this means it extends in time from -infinity to +infinity. Thus, one can talk about inversions as being the same as a 180 degree phase shift. Further we map everything into a mod 2*Pi phase range.


pfalcon:

We do not care about currents or the direction of windings in the transformer or whether the secondary it is a single piece of wire tapped in the center or two separate essentially identical coils.

So to repeat consider two coils. One coil is labeled X1 with a DOT on X1 and the other end is X2 no DOT. The second coil is X3 with a DOT on X3 and its other end is X4. These coils are excited from the same source so that their frequencies and amplitudes are identical. The excitation is such that when at exactly the same time the first coil's X1 is more positive than X2, then X3 is more positive than X4.

If X2 is connected to X4 as the start of paralleling the two coils, then what is the voltage between X1 and X3? Can you finish paralleling these coils? Is there any circulating current? Are these two voltages "in-phase" or "out-of-phase"?

If X2 is connected to X3 as the start of paralleling the two coils, then what is the voltage between X1 and X4? Can you finish paralleling these coils? Is there any circulating current? Are these two voltages "in-phase" or "out-of-phase"?

These voltages can be described as V_X1-X2 and V_X3-X4 for the assigned location of the phasing DOTs.

.

 

[Rick Christopherson]

Rick Christopherson:

Your comment about noise has no bearing on the discussion. The discussion is based on a sine wave signal, meaning a sine wave shape and only one frequency. Further by assumption the signal is steady state and ideally this means it extends in time from -infinity to +infinity. Thus, one can talk about inversions as being the same as a 180 degree phase shift. Further we map everything into a mod 2*Pi phase range.

The example with the noise was not intended to focus on the actual waveform, but to make it easier to understand that the function of reversing test leads or reference points is an inversion that we (may choose to) mathematically transform into a 180 degree phase shift.

The topic was broached because several of the respondents were stating that the phase shift was a physical property, and specifically not being mathematical. But in reality, the inversion is a physical change and the phase shift is a mathematical identity that we may use. It has a direct bearing on the discussion because these individuals were claiming it to not be mathematical in nature.

V_AB(t) = -V_BA(t) is a physical property of the system

-V_BASin(wt) = V_BASin(wt?180?) is a mathematical transformation

Furthermore, only Rattus (and now yourself) have ever claimed that this discussion needed to be limited to ideal mathematical functions. Beseoker specifically dealt with real signals by bringing in so many photographs and discussions of his oscilloscope. Additionally, any time someone questioned using two reference points would quickly be met with comments about how that would let the smoke out of their real scopes.

As I have said many times in this discussion, if it were left in the ideal mathematical realm, I wouldn't be contesting anything that was said. I enter the discussion only because so many of the respondents make statements of the real world based on their ideal mathematical model.

 

[gar]

120201-1622 EST

Rick:

If I do it with a resolver or an LVDT instead of a transformer is it physical or mathematical? What is the meaning of phase shift? Is an RC network real or mathematical?

Gone for a while to the energy meeting.

.

 

[Rick Christopherson]

120201-1622 EST

Rick:

If I do it with a resolver or an LVDT instead of a transformer is it physical or mathematical? What is the meaning of phase shift? Is an RC network real or mathematical?

Gone for a while to the energy meeting.

.

But we're not talking about resolvers or LVDT's. We're talking about center-tapped single phase transformers. I am not disputing those cases where a phase shift is physical. This is not one of those cases, and the phase shift is purely mathematical. Why can't you guys stay on the actual topic?

 

[rbalex]

120301-1505 EST

rbalex:

I will respond to you sometime later. I really do not know the basis of your argument. That I am trying to figure out.

...

Every relevant voltage function however validly determined in a conventional 120/240V system, either initially or replaced by identiities, can be written in terms of the same phase.

V(t) = V_m sin (ωt + φ₀) here V_m is of the set [120, -120, 240, -240], ω and φ₀ are positive constants, and t₀ is arbitrary, but common, to all functions.

The expression "(ωt + φ₀)" is the identical phase of each relevant voltage function; i.e., φ(t) = sin (ωt + φ₀).

So V(t) = V_m φ(t) is also valid for all relevant voltage functions.

 

[pfalcon]

You don't need to to call anyone. If the phasor arrows are connected tail to tail, you SUBTRACT. If the phasor arrows are connected head to tail, you add, phasorially that is.

Nope. Phasor math is independent of head-tail or tail-tail. You add. That's why you used a phasor in the first place. The direction shows the math in visual form. You're supposed to be able to draw the solution with phasors.

 

[pfalcon]

Well, what is the phase for

sin(wt + 179)??

A distorted power factor across the secondary coil. Still just one phase, just not PF 1.

 

[pfalcon]

But going in opposite directions. That cannot reasonably be construed as the same phase.

Hmm. Let's see. If I look at the instantaneous current and measure V_an to get 120<0 in the direction of current flow, then I measure V_bn against the direction of current flow to get 120<180, then I remember to correct the reading for V_an to match the current flow for V_bn or vice versa: Then the traces match exactly with the same polarity, same zero crossing, same magnitude.

But if I forget that voltage is only a measurement of those pesky little charges of energy and don't correct for their instantaneous direction of travel. Why ... then I can call everyone who disagrees unreasonable.

 

[pfalcon]

BTW, I have never seen trig identities used in that manner. I doubt that anyone else has either.

Yes, I've done it repeatedly. But then, I've gone through the exercise of deriving the more complex derivatives in calculus from the simple derivatives.

 

[pfalcon]

I am not questioning the identity. I am questioning the conclusions reached by rbalex where he claims (wt + 180) = (wt). He has made the phase constant disappear. I am asking for a reference to support this position.

Um, actually you're either questioning the identity or how it's applied; because the rest is just cranking the math. He didn't make anything disappear. It grinds to equivalence on the calculator.
You're effectively asking for references to support that his calculator punches out results correctly. It does and it did. Therefore the error, if it exists, can only be in the identity or in how it's applied.
The rest below the equation setup is axiomatic cranking.

sin(u ? v) = sin (u)cos (v) ? cos(u)sin(v)
substituting u = wt and v = 179

 

[pfalcon]

At least four engineers, with decades of experience think you are wrong.

And at least four engineers, with decades of experience think he's right.

Problem is that some members may actually believe your claims.

Then they learned something you haven't.

 

[pfalcon]

Why would I invert one of the waveforms? I want the waveforms on L1 and L2, not their inverses.
And, what does current have to do with anything?

LoL. Why do you think voltage has anything to do with it? The phase of a system is all about how the power is flowing. It doesn't care what your voltage readings are. It doesn't care what your oscilloscope shows. It only cares where those little coloumbs of charge are and where they're going. The primary electric field pushes them all in the same direction at the same time with the same force. It doesn't push them "toward" or "away" from anything. Unless you correct for the direction those charges are moving then you're equations and assertions are fictional.

BTW, it is wt = 0 and wt = 180. t is measured in seconds, not degrees. Cap T is standard notation for the period, a constant, not a function of time.

Lovely attempt to derail the discussion again. Despite your knowing how it was used. Unless, gasp, you really did believe I was referring to phase offset of 90 degrees instead of referring to the instantaneous state at 1/4 cycle?

 

[rattus]

And at least four engineers, with decades of experience think he's right.


Then they learned something you haven't.

Perhaps then you could provide a valid reference which supports your position?

 

[pfalcon]

pfalcon:

Since you addressed me expressly.

We do not care about currents or the direction of windings in the transformer or whether the secondary it is a single piece of wire tapped in the center or two separate essentially identical coils.

Which is why you can't resolve this. It's all about the coloumbs of charge passing through the windings. Not the voltage. Not the current. The energy movement determines the phase and nothing else. The instantaneous current is the best indicator. Solve at 1/4 or 3/4 cycle and the results come out correctly.

So to repeat consider two coils. One coil is labeled X1 with a DOT on X1 and the other end is X2 no DOT. The second coil is X3 with a DOT on X3 and its other end is X4. These coils are excited from the same source so that their frequencies and amplitudes are identical. The excitation is such that when at exactly the same time the first coil's X1 is more positive than X2, then X3 is more positive than X4.

If X2 is connected to X4 as the start of paralleling the two coils, then what is the voltage between X1 and X3? Can you finish paralleling these coils? Is there any circulating current? Are these two voltages "in-phase" or "out-of-phase"?

If X2 is connected to X3 as the start of paralleling the two coils, then what is the voltage between X1 and X4? Can you finish paralleling these coils? Is there any circulating current? Are these two voltages "in-phase" or "out-of-phase"?

These voltages can be described as V_X1-X2 and V_X3-X4 for the assigned location of the phasing DOTs.

Gar, your primary coil induces the charges in the winding to move from X1 & X3 to X2 & X4 at 1/4 cycle. Reverse at 3/4 cycle. Your second "parallel" is called a dead short. ALL the voltages, ALL the time, are ALL the same phase. They're all the same phase because they're all induced by the same EMF force and it can't be two things at once.

Which takes us back to the top quote. If you ever want to deterministically verify why 120/240 is called single phase then you must be attentive to the flow of energy through the windings. Which technique you use is not really relevant. What is relevant is that you compare measurements that are based on the thing that is determining phase in the first place - the induced energy flow. And like all good phasor diagrams and instrument readings, when you reverse the physical direction of measurement then you must invert the polarity of the measurement. Otherwise you're just fooling yourself.

But let's go back to that voltage "in-phase" or "out-of-phase" thing. It's axiomatic that the two opposing ends of the secondary must always measure in opposition. The coil is a simple voltage divider with three taps A, N, B. When A goes high at 1/4 cycle then N is low and B lower. B is the other END of the Voltage Gradient. They reverse at 3/4 cycle. When we fix N at 0V we haven't changed a thing in their relationship other than how we LOOK at it. At 1/4 cycle A is still higher than B. At 3/4 cycle B is still higher than A. Perceptually they are "out-of-phase". Pragmatically they are 180 degrees out-of-phase. Physically they'll cook your hand. And none of the dozen peeps arguing this thread have ever tried to claim otherwise. Though there've been many stumbles in trying to get the words right.

So, why it's called single phase can only be expressed in the context of what drives the phase of the system. The primary winding's induction of the secondary is EVERYTHING that's important about determining why we call it single phase power. Neglecting the induction field leads to misunderstanding the label.

 

[mivey]

two phases

two phases

On two 180? phases:
Experiments in the 1860's were carried out to see if you could combine two smaller forces to create a larger force. They found they could combine both in-phase forces and phase-opposed forces. Either way, the result was one larger single-phase force.

As a result, we know today that two in-phase voltages can be combined to produce a larger single-phase voltage. We also know two phase-opposed voltages can be combined to produce a larger single-phase voltage.

As for 180? two-phase:
The way C.P. Steinmetz and others have explained it, if we take the negative phase to be the return circuit of the positive phase, the result is a larger single phase circuit. Therefore, the second-order symmetrical polyphase system combines into one larger first-order system. That is why the numbering of symmetrical polyphase systems starts with three, not two (the historic non-symmetrical two-phase is actually part of a four-phase, or quadrature, system).

However, Steinmetz did not say that the combining of two smaller phases into a larger single-phase "wiped out" the smaller phases. When observing that the four-phase system also had opposing pairs of E and -E as well as jE and -jE, he noted that the four e.m.fs of the quadrature system were in pairs opposite to each other and

Hence can be produced by two coils in quadrature with each other, analogous as the two-phase system, or ordinary alternating current system, can be produced by one coil.

In the center-tap winding, the in-phase voltages will be present as two smaller voltages taken in series from end to end, and the phase-opposed voltages will be present as two smaller voltages taken from the common point. We do indeed have a large single-phase voltage present but we can also extract out two smaller in-phase voltages or two smaller phase-opposed voltages. The simple fact is that both in-phase and phase-opposed voltages are present at the center-tapped winding and we can use them either way.

 

[mivey]

"not in phase" but same phase?

"not in phase" but same phase?

On "not in-phase" waveforms having the same phase:
The truth of the matter is for phase-opposed waves, you can invert one of the waveforms and the inverted waveform will have the same phase points as the other waveform. In other words, the inverse of one wave is in phase with the other wave. Nothing new, and we all know this.

But to say both original waveforms have the same phase is incorrect. Our industry does not agree with that, reference texts do not agree with that, textbooks do not agree with that, and our universities do not teach that. Anyone who says both original waveforms have the same phase is simply mis-interpreting the definition of phase because that interpretation conflicts with the way the rest of our industry interprets the definition of phase.

The phase constant is defined by the initial conditions of the waveform. It is silly to say that there is a phase constant plus some other adder that can be removed because it only results in a negative sign. Anyone familiar with the physics of oscillating systems and the accompanying math knows that is the same as saying two springs moving in opposite directions is the same as two springs moving in the same direction. It just ain't so, and you will not find a credible reference that says it is the same.

What the trig reduction says is that if we have two springs oscillating in opposite directions, and we reverse the direction of one spring, then the two springs will oscillate in the same direction. Well duh.