Why is residential wiring known as single phase?

[mivey]

Then why do you continually insist on using words like "real" and "physical" if you are not willing to defend them?

I choose to stick to the topic at hand which is the voltages and the associated phase relationships we get from transformers. I have defended my usage per the topic at hand. Your choice to talk about how the term phase is used with things other than transformers and about time shifts that are not really relevant to what I am talking about.

I simply choose not to engage in a discussion about a different topic, other than to say that the phase shifts we get from the transformers are not time shifts. But since we are not talking about those type shifts anyway, so what? Keep talking about a time shift if you want, but it is not the topic I am discussing in this thread. I feel no obligation to defend something I am not discussing nor do I feel obligated to engage in a debate over something I am not discussing.

You chose those words for a reason and you accentuated them repeatedly for a reason.

I use those words because of what has been recognized to be a phase shift by taking voltages from different terminals and in different winding directions. That is the real shift I am discussing. It is factually incorrect to say that these physical manipulations can produce a phase shift in transformers, but then if we look at the two windings all by themselves the phase shift goes away.

Looking at a single-phase transformer: As part of a larger configuration, the change in winding direction produces a phase shift for the voltage from that winding and this is recognized in the numerous references I have posted. Looking at that winding as part of a larger configuration vs. looking at it by itself does not change anything because the physical action and physical reaction is exactly the same in both cases.

The facts as supported by the posted references is that taking a voltage in a different winding direction produces a phase shift for that voltage. The fact is that it can do the same whether the transformer is by itself or used as part of a larger configuration. The physical action and physical reaction is exactly the same.

 

[mivey]

You because you are old does not make you correct.

Not what I said. My point was that someone who has been around the block should be familiar with the terminology as used with transformers.

Utilities references are notorious for using the single word 'phase' when in context it is clear that they are addressing 'conductors'.

That is why I have provided sources beyond just utilities.

I am comfortable with a mathematical inversion being the same phase as the original and yet also acknowledge there is difference between an inversion and an opposing phase.

The evidence from the numerous references posted shows that an inversion has been recognized to produce a phase difference. That is simple fact. It is the phase difference we get by physically manipulating the terminals we use and the winding direction we use. It is common practice and terminology for transformers.

A single waveform is a single wave form, regardless how you manipulate its magnitude.

With a two-wire source, we only have a single waveform. With the three-wire source, we are not limited to one waveform.

 

[Rick Christopherson]

You're running away Mivey. The discussion is very much relevant to the topic. The question is "why is this called single phase", and the answer is because there is only one physical phase angle. The apparent phase shift is mathematical, not physical. So there is only one. So whether you want to deny it or not, this is very much relevant to the topic.

 

[gar]

120316-0943 EDT

rbalex:

I disagree with your analysis and conclusion.

The IEEE definition in my opinion says nothing about the comparison of different functions. I believe the only definition it is providing is:

1. A way to define a displacement on the x-axis within a periodic function based on the period of the function.

Basically it defines a yardstick with a length of one period, and calibrated from 0 to 1.0 over the length of the yardstick. This yardstick can have its 0 point positioned anywhere in the period. Further it allows the yardstick to be used over multiple periods by using N periods as an offset of its 0 position.

The IEEE definition seems to be specifying that phase measurements are made in fractions of a period (non-dimensional) vs degrees or radians or something else.

I do not believe the IEEE definition says anything about comparison of two or more waveforms. Therefore, for you to make comparisons it is necessary to define how you will use this IEEE yardstick.

I do not agree with your implied definition of coincident zero crossings without consideration of slope as being of the "same" phase.

I believe that before you can use your "therefore" conclusion that you need to define how more than one waveform (different functions) are going to be measured with the IEEE yardstick.

.

 

[jim dungar]

With a two-wire source, we only have a single waveform.

Discussing the phase relationship between Vbn and -Vnb, which seems to be Rattus' focus, involves a single waveform.

A transformer physically wired Vx1x2 connected to Vx3x4 produces a single waveform Vx1x4. This is the reality of the winding interconnections. How you manipulate, fondle, measure, use, or abuse the individual voltages of Vx1x2 and Vx3x4 is strictly arbitrary, but none of that changes the actual result of a single voltage, Vx1x4, with a single waveform. Physically connecting the windings in a different manner, is the only way to get different results.

 

[rattus]

Discussing the phase relationship between Vbn and -Vnb, which seems to be Rattus' focus, involves a single waveform.

A transformer physically wired Vx1x2 connected to Vx3x4 produces a single waveform Vx1x4. This is the reality of the winding interconnections. How you manipulate, fondle, measure, use, or abuse the individual voltages of Vx1x2 and Vx3x4 is strictly arbitrary, but none of that changes the actual result of a single voltage, Vx1x4, with a single waveform. Physically connecting the windings in a different manner, is the only way to get different results.

A centered tapped secondary provides a 3-wire source; said 3-wire source provides two voltages; said voltages are inverses of each other; said inverted waveforms are in opposition; said opposing waveforms are PI radians out of phase. It is that simple.

mivey has recently posted numerous references supporting these facts, and it is obvious by looking at the plots of said waveforms.

Let me ask you this: If you didn't know these voltages were obtained from a single phase transformer, would that change your position?

 

[gar]

120316-1048 EDT

Rick:

I do not believe that anyone is arguing that it is not a "single phase" service from the perspective of a useful name. Admittedly the original question was "why is residential wiring known as single phase", and there has been very little real discussion on that aspect. But what has resulted is, in my opinion, answers that are not logically valid, and that is where the argument has been.

In normal use in a power distribution application to a typical house the single phase transformer with a center tapped secondary never sees loads connected to the secondary that from a load input perspective are not single phase loads. I can put a two phase load on it by connecting two diodes to my 240 V supply and use the power company transformer as part of a "full wave center tapped rectifier circuit", but I have no reason to do this at the moment.

Mathematical, real, apparent, physical, switching test leads, etc. do not matter. You cannot connect X1 to X4 where X2 and X3 are the neutral point with power applied to the primary and not cause sparks and excessive current flow. Clearly the reason is that V_X1X2 is not equal to V_X4X3. By my definition and many others these two voltages are 180 degrees "out-of-phase".

.

 

[Rick Christopherson]

By my definition and many others these two voltages are 180 degrees "out-of-phase".

So in other words, you want to ignore any part of the discussion that does not kowtow to your definition. Makes for a rather one-sided discussion, wouldn't you agree? If you guys are not arguing whether there is one versus two phase angles, then what exactly are you arguing?

 

[jim dungar]

Let me ask you this: If you didn't know these voltages were obtained from a single phase transformer, would that change your position?

Your arguments have consistently mentioned Vbn and -Vnb: this is one voltage and one waveform, one phase.

Adding Van creates a second waveform.
Two voltages require two waveforms.
Two waveforms require a common reference. A common reference for transformer is the relationship between the primary and the secondary (i.e. 0? shift with a delta-delta or 30?shift with a delta-wye).

But as soon as you employ an equality based on a 1:1 ratio, like Van=Vnb or any of its variances, you bring us back to a single voltage and a single waveform and therefore a single phase.

 

[jim dungar]

Mathematical, real, apparent, physical, switching test leads, etc. do not matter. You cannot connect X1 to X4 where X2 and X3 are the neutral point with power applied to the primary and not cause sparks and excessive current flow. Clearly the reason is that V_X1X2 is not equal to V_X4X3. By my definition and many others these two voltages are 180 degrees "out-of-phase".

.

You cannot connect X1 to X2 or X3 to X4 "with power applied to the primary and not cause sparks and excessive current flow" either. Let it go on the record, Gar says there is a potential difference (voltage) between the two ends of a length of wire in an alternating magnetic field.

 

[gar]

120316-1228 EDT

Jim:

You do not understand what we are trying to point out.

Correct you can not connect X1 to X2 without sparks, but we are talking about a 3 or 4 terminal device. Thus, we have at least two or more voltages to consider.

The easiest way to prove that V_X1X2 and V_X4X3 are not identical signals is to connect X2 to X3 (make it equivalent to a center tapped secondary), and then ask the question what is the voltage difference between X1 and X4. If this voltage is noit zero, then the signals are not identical.

If instead of connecting X2 to X3 we connect X1 to X3, then the difference between X2 and X4 is zero and X2 can be connected to X4, Now the voltages voltages V_X1X2 and V_X3X4 are identical.

With X1 connected to X3, one diode anode connected to X2 and a second diode anode connected to X4, and both diode cathodes connected, then is this a half or full wave rectifier?

.

 

[rattus]

Your arguments have consistently mentioned Vbn and -Vnb: this is one voltage and one waveform, one phase.

Adding Van creates a second waveform.
Two voltages require two waveforms.
Two waveforms require a common reference. A common reference for transformer is the relationship between the primary and the secondary (i.e. 0? shift with a delta-delta or 30?shift with a delta-wye).

But as soon as you employ an equality based on a 1:1 ratio, like Van=Vnb or any of its variances, you bring us back to a single voltage and a single waveform and therefore a single phase.

Jim, you didn't answer the question.

No, a reference is a node which in this case is the X2-X3 node on the transformer. It is also the neutral node.

Let me say this, the practice of using the neutral as a reference and saying that the voltages seen on L1 and L2 are out of phase by PI is well established.

 

[gar]

120316-1249 EDT

Rick:

I really do not understand your response.

So in other words, you want to ignore any part of the discussion that does not kowtow to your definition. Makes for a rather one-sided discussion, wouldn't you agree? If you guys are not arguing whether there is one versus two phase angles, then what exactly are you arguing?

I do not agree with rbalex's statement, and I have a number of references that are different than his. It is clear that there is no direct link from the IEEE definition of phase to rbalex's conclusion without him postulating other conditions.

We are not ignoring anything.

In mathematics you can postulate certain basic items, then from these draw some absolute conclusions, but absolute relative to the postulates.

In non-mathematical areas definitions are based on general usage, and usually this is documented in a dictionary.

I am not going to agree with a definition that says two waveforms are the same phase if their zero crossing are coincident. This serves no use purpose for me.

I am using the description "my definition" to avoid having you claim I am misinterpreting someone else's definition. I have pointed out a number of references that are consistent with my definition.

One thing we are arguing is that the inversion or 180 degree phase shift of a sine wave is not the same phase as the reference (the non-inverted wave).

.

 

[Rick Christopherson]

Rick:

I do not agree with rbalex's statement, .....

And I'm not Rbalex. So why are you presenting his argument to me? I have never presented my argument to you, except for when you have commented on it. You've voluntarily jumped into it and commented on it. My argument has been with those individuals that are falsely trying to bolster their position by stating that a real and/or physical phase shift exists that they have emphatically claimed was not just mathematical. It does apply to the overall discussion, because it is being stated and used as it pertains to whether there is a single phase angle versus two phase angles.

You guys can argue mathematics until you're blue in the face, and it will never be resolved, because you can never disprove one mathematical contention over the other. Both positions can put together a formal math proof, and both of those proofs will be correct. So there is absolutely no reason to be mathematically butting heads.

 

[ggunn]

I've come in late and I'm not reading all 200+ pages of this, but it's really just a question of reference point, isn't it? If you apply an AC waveform to the primary of a transformer with a center tapped secondary, you can pick any terminal of the secondary you like and look at the waveforms on the other two referenced to it. Call the secondary terminals A, B, and N, with N being the center tap. If you reference A, then the sine waves on N and B will be identical except that N will have half the amplitude of B. If you reference B, then A and N will be the same except N will have half the amplitude of A. If you reference N, then A and B will have the same amplitude (the same as N had in the previous two cases), but their polarity will be the opposite of each other. It's all still single phase because all you are doing is looking at the same single phase waveform from different reference points.

Is it really any more complicated than that? I'll hang up and listen...

 

[gar]

120316-1425 EDT

Rick:

Why did I mention rbalex in my response to you is because you stated

So in other words, you want to ignore any part of the discussion that does not kowtow to your definition.

Something you might want to discuss relative to phase shift and inversion is what happens if the excitation is a sawtooth. Meaning it starts at -V, goes thru 0 at PI (0.5 period), and to +V at 2*Pi (one period). There is no phase shift that produces a result equivalent to an inversion. A full wave center tapped rectifier will be similar to that of one fed from a sine wave. Still a ripple with a double frequency fundamental component.

.

 

[ggunn]

120316-1425 EDT

Rick:

Why did I mention rbalex in my response to you is because you stated

Something you might want to discuss relative to phase shift and inversion is what happens if the excitation is a sawtooth. Meaning it starts at -V, goes thru 0 at PI (0.5 period), and to +V at 2*Pi (one period). There is no phase shift that produces a result equivalent to an inversion. A full wave center tapped rectifier will be similar to that of one fed from a sine wave. Still a ripple with a double frequency fundamental component.

.

As you say, inversion and phase shift are not the same thing. Phase shift is a function of time delay. This is a common error in audio terminology; folks often talk of signals being "out of phase" when they really mean "reverse polarity". In waveforms more complex than pure sine waves they are not even remotely the same.

 

[jim dungar]

120316-1228 EDT

Jim:

You do not understand what we are trying to point out.

I know what you are trying to point out, you just don't admit it doesn't matter.

There is a single winding in the transformer X1 to X4, you cut it in half, you have two IDENTICAL windings X1 to X2 and X3 to X4. Referenced to the primary winding you now have two of the EXACT voltage (magnitude and direction), therefore you have identical waveforms.

What you do with the voltages Vx1x2 and Vx3x4 is your private business. But anything you do to them is purely mathematical, when referenced to the magnetic field that created them. You may call one V12 and the other V43, but then you need to acknowledge you have swapped the reference direction, and then account for this inversion in all of your formulas that involve both identical windings

The physical connection of the transformer is still X1 to X4. Of course, the opposite ends of a single winding are not the same point, but that is not due the fact you created a midpoint in the transformer.

 

[Rick Christopherson]

Something you might want to discuss relative to phase shift and inversion is what happens if the excitation is a sawtooth. Meaning it starts at -V, goes thru 0 at PI (0.5 period), and to +V at 2*Pi (one period). There is no phase shift that produces a result equivalent to an inversion. A full wave center tapped rectifier will be similar to that of one fed from a sine wave. Still a ripple with a double frequency fundamental component.

Yes. Thank you. I know there are many examples that can be used, and this one is quite good. I chose the noise example because even in power systems, noise is a legitimately observed signal.

I do like your example, though, because it refutes many points all at once. You are correct. There can be no inversion that looks like a phase shift. In the bridge rectifier situation, the output will look like an "M" for an inversion, but a frequency doubled sawtooth of it is phase shifted.

 

[rattus]

I've come in late and I'm not reading all 200+ pages of this, but it's really just a question of reference point, isn't it? If you apply an AC waveform to the primary of a transformer with a center tapped secondary, you can pick any terminal of the secondary you like and look at the waveforms on the other two referenced to it. Call the secondary terminals A, B, and N, with N being the center tap. If you reference A, then the sine waves on N and B will be identical except that N will have half the amplitude of B. If you reference B, then A and N will be the same except N will have half the amplitude of A. If you reference N, then A and B will have the same amplitude (the same as N had in the previous two cases), but their polarity will be the opposite of each other. It's all still single phase because all you are doing is looking at the same single phase waveform from different reference points.

Is it really any more complicated than that? I'll hang up and listen...

No, not really. It would be helpful though if you would state your opinion on the following bones of contention:

An inversion produces a PI radian phase shift.

A center tapped transformer splits the single phase of a residential system into two voltages with two phase angles, therefore two phases.

A sine wave cannot carry the same phase as its inverse. Neither can it be in phase with its inverse.

Signs do matter with trig identities.

The use of the neutral as a reference point is widely accepted.