Why is residential wiring known as single phase?

[T.M.Haja Sahib]

Then I couldn't possibly know how to make controlled rectifiers at 40,000Adc configured as 24-pulse systems.
But I do.
I design, manufacture, test, and commission them.
And variable speed DC drives, inverters, DC choppers, sub-synchronous converter cascades.
Oh yes. And all the electronic controls needed to go with them.

Not too bad for someone who is ignorant about the difference between direct current and alternating current.
Maybe I'll put my abysmal ignorance into practice for a few years yet.

You are a marvelous engineer.
I wonder why you can not accept a 120/240v supply as a single phase.

May the following may convince you towards it.

D.C
120V, -120V

A.C
120V,-120V

What are the differences between the two sets of DC and AC voltages above?

 

[mivey]

You are a marvelous engineer.
I wonder why you can not accept a 120/240v supply as a single phase.

May the following may convince you towards it.

D.C
120V, -120V

A.C
120V,-120V

What are the differences between the two sets of DC and AC voltages above?

The DC does not have voltages that reverse direction so there is no varying phase and the voltages are just flat lines. The AC reverses direction at regular intervals and the waveforms have a phase that various with time.

 

[T.M.Haja Sahib]

The DC does not have voltages that reverse direction so there is no varying phase and the voltages are just flat lines. The AC reverses direction at regular intervals and the waveforms have a phase that various with time.

mivey,I did not expect you would try to answer it.

But still you did not answer it the way I expected.

Let Bes try so that he may come to our side.

 

[mivey]

Let Bes try so that he may come to our side.

I do not disagree with what he posted so I'm not sure what you are getting at. Often that is the case.

 

[mivey]

With a phase angle meter,measure phase angle differences...

FWIW, the phase angle meter measures all phase angles from 0? to 360?. It does not "resolve" to zero at 180? but rather "resolves" to zero at 360?.

 

[jim dungar]

Everything we are discussing is about how they appear.

Don't I remember a disagreement on using the word appear as implies "fake"?

I do not know any one that has said different mathematical models are not valid.
But there is only one actual real life physical connection a transformer's center-tapped winding.
If multiple transformer windings are physically wired incorrectly the results will not match those predicted by a model.

The real world does matter.

 

[mivey]

I do not know any one that has said different mathematical models are not valid.
But there is only one actual real life physical connection a transformer's center-tapped winding.
If multiple transformer windings are physically wired incorrectly the results will not match those predicted by a model.

The real world does matter.

But you haven't really answered this question though have you?:

Do you take issue with the model I have in my graphic? Are you saying this it is not a physically-realizable model?

My graphic illustrates that the reference frame used is a choice and is not universally dictated. There is no real world universal reference frame.

Are the forces in the coil working together? Of course they are. But that would happen with voltages that have a 0? displacement in one reference frame as well as with voltages that have a 180? displacement in a different reference frame. Voltage is relative to the reference frame and we have to choose a reference frame before we talk about the voltages having or not having a phase displacement.

 

[rbalex]

Several folks have attempted to show me my error by demonstrating in various unnecessary and often highly complex ways, what essentially boils down to:

a ≠-a​

Of course, that?s true.

So let?s keep this simple:

a ≠-a
1 x a ≠-1 x a or
a x 1 ≠-1 x a ​

Factoring out the inequality [1 ≠-1]

a = a, in fact,
a Ξ a​

Now consider two physical phenomena characterized as functions of time by:

?₁(t) = A₁ P (ω₁t+φ₁) [1]
?₂(t) = A₂ P (ω₂t+φ₂) [2]​

Where P is an arbitrary periodic function (typically, but not necessarily Sine or Cosine), A_1,and A₂ are amplitude constants, ω₁ and ω₂ are frequency constants, φ₁ and φ₂ are initial value constants and t is an independent variable common to both.

Using the definitions of ?in sync? and ?phase? cited by rattus as:

"In synch" indicates that the outputs of two or more generators in parallel are all in phase. That is, the generators are operating in synchronism.
[Puchstein, Lloyd, and Conrad, Alternating Current Machines, Wiley, 1954]

Phase: Phase is the fractional part of a period through which time or the associated time angle wt has advanced from an arbitrary reference
[Kerchner and Corcoran, Alternating-Current Circuits, Wiley, 1951]

Note the definition of phase says nothing of magnitude (amplitude) or sign (polarity)

The phenomena ?₁(t) and ?₂(t) are synchronized (?in-sync?) if, and only if:

A₁ = A₂, (which asserts both amplitude and polarity are necessary for synchronism)
ω₁ = ω₂ and
φ₁ = φ₂
​

They have the same phase ("in phase") if, and only if:

ω₁ = ω₂ and
φ₁ = φ₂
​

Magnitude (amplitude) and sign (polarity) of A₁ and A₂ are irrelevant.When the phenomena are ?in-sync" they must also be ?in-phase,? but they are not necessarily ?in-sync? if they are ?in-phase.?

Colloquially, we tend to use the terms ?in-phase? and ?in-sync,? as if they are synonymous. Most of the time, doing so is no big deal. We generally know what each other means; but for answering the question,?Why is residential wiring known as single phase?? it is necessary to distinguish them.

 

[jim dungar]

There is no real world universal reference frame.

No single universal reference frame - are you implying that I said there was? Besoeker and Rattus are some of those that seem to be fixated on a single reference point.

Are you saying that actual physical connections are irrelevant?

Does your graphic represent the actual connections of a transformer with a single primary winding and a center-tapped secondary winding?
Does your graphic represent the actual connections of a transformer with a single primary winding and a two reconnectable (series or parallel) secondary windings?
Again, I don't think anyone has denied, that two actual "out of phase" sources can be connected to create 120/240V and that two actual "in phase" sources can be connected to create 120/240V.
So we are back to the original topic, is a center-tapped transformer actually connected in phase? There is a yes or no answer.
A follow up question becomes, are the two identical 120V secondary windings X1-X2 and X3-X4 of a standard reconnectable transfomer physically connected in phase? Again there is a correct answer.

So there can be physically correct answers that are not universally applicable. And, there can be technically correct models that cannot be replicated in the physical word.

 

[pfalcon]

No problems so far, so carry on. But, please review my graphic that I just posted as it may answer some questions and might save you some typing.

Sadly, my system kicks the photobucket.

You can have 4 reference frames:
1) Positive away from one end
2) Positive towards one end
3) Positive away from neutral
4) Positive towards neutral

Just an aside, cases 3) and 4) are where you and I are in flames. They're the scarecrow telling Dorothy which road to take.

Is it potential or voltage that has no universal reference?

Potential is properly "potential difference". Volts are the unit of measure agreed upon to measure that. The polarity of voltage is usually considered in relation to the direction of current flow.

Since in an AC circuit the current alternates direction, the choice of Positive or Negative is arbitrary but should remain constant for the system being analyzed.

Mivey is arguing that the choice of direction for the "left-hand" side of the secondary coil is independant of the choice for the "right-hand" side. Therefore cases 3) and 4) above would be valid. Mivey's system will pass any mathematical or trace test you propose as long as you permit that assumption. And although you may reject that assumption, Mivey will not. Therefore your math and scope tests will continually fail to persuade him.

 

[mivey]

Note the definition of phase says nothing of magnitude (amplitude) or sign (polarity)

The phase represents a location on the wave relative to a reference point. It does not "reset to zero" half-way through the cycle of the wave. Consider the use of the phasor diagram and how the angles vary from 0? to 360?.

We can track the change in the phase over time by plotting a vector that rotates from a reference axis. As the wave moves through the complete cycle, the phase changes from 0? to 360?. There is no "re-setting" of the phase angle when we reach the half-way point and I doubt you will find any valid text to support that claim. What I have stated is common knowledge and is found in any good textbook dealing with oscillating systems (at a minimum I know it is in my calculus textbooks, physics textbooks, and in my signals & systems textbooks. I have several of each in my library but can't get there now.

The positive and negative vectors point in opposite directions and their phase angle from the reference axis differs by 180?, not zero degrees. Cross two terminals with voltages having a 180? phase difference and you will find out quickly that they are not in phase but will get a quick lesson in interference between two waves that are not in phase.

 

[mivey]

No single universal reference frame - are you implying that I said there was? Besoeker and Rattus are some of those that seem to be fixated on a single reference point.

Your statements continue to reflect the idea that there is only one real physical reference and that is from end to end across the winding. I agree that the forces are in phase across the winding.

Are you saying that actual physical connections are irrelevant?

No. Are you thinking that the direction of a voltage rise or fall is based on a physical location? Do you not agree that voltage itself is relative to a reference and that the choice of reference is not determined by the physical configuration?

Does your graphic represent the actual connections of a transformer with a single primary winding and a center-tapped secondary winding?

Yes. That is exactly what is feeding in from the right side of my graphic.

Does your graphic represent the actual connections of a transformer with a single primary winding and a two reconnectable (series or parallel) secondary windings?

No. I had no interest in a parallel connection, only a series connection like we have in the residential transformer.

Again, I don't think anyone has denied, that two actual "out of phase" sources can be connected to create 120/240V and that two actual "in phase" sources can be connected to create 120/240V.

It is hard to tell sometimes. My position is that the reverse operation is also possible.

So we are back to the original topic, is a center-tapped transformer actually connected in phase? There is a yes or no answer.

Yes. That is why it is called a single-phase transformer.

A follow up question becomes, are the two identical 120V secondary windings X1-X2 and X3-X4 of a standard reconnectable transfomer physically connected in phase? Again there is a correct answer.

Yes. That is why it is called a single-phase transformer.

So there can be physically correct answers that are not universally applicable. And, there can be technically correct models that cannot be replicated in the physical word.

I am not saying the forces in the transformer are out of phase. I am saying a 120/240V can create two actual "out of phase" sources and that a 120/240V can create two actual "in phase" sources. As such, it can be a source for both "out of phase" and "in phase" voltages.

The people who ask these questions have usually seen both voltage sets and are not digging around in the transformer windings. From what I can gather, there are some that contend that the "out of phase" set does not really exist because they can not exist in the center-tap transformer windings (not saying that is your position). My graphic shows that they can, and do, exist in the center-tap transformer windings

 

[rattus]

Several folks have attempted to show me my error by demonstrating in various unnecessary and often highly complex ways, what essentially boils down to:

a ≠-a​

Of course, that’s true.

So let’s keep this simple:

a ≠-a
1 x a ≠-1 x a or
a x 1 ≠-1 x a ​

Factoring out the inequality [1 ≠-1]

a = a, in fact,
a Ξ a​

Now consider two physical phenomena characterized as functions of time by:

ƒ₁(t) = A₁ P (ω₁t+φ₁) [1]
ƒ₂(t) = A₂ P (ω₂t+φ₂) [2]​

Where P is an arbitrary periodic function (typically, but not necessarily Sine or Cosine), A_1,and A₂ are amplitude constants, ω₁ and ω₂ are frequency constants, φ₁ and φ₂ are initial value constants and t is an independent variable common to both.

Using the definitions of “in sync” and “phase” cited by rattus as:

Note the definition of phase says nothing of magnitude (amplitude) or sign (polarity)

The phenomena ƒ₁(t) and ƒ₂(t) are synchronized (”in-sync”) if, and only if:

A₁ = A₂, (which asserts both amplitude and polarity are necessary for synchronism)
ω₁ = ω₂ and
φ₁ = φ₂
​

They have the same phase ("in phase") if, and only if:

ω₁ = ω₂ and
φ₁ = φ₂
​

Magnitude (amplitude) and sign (polarity) of A₁ and A₂ are irrelevant.When the phenomena are “in-sync" they must also be “in-phase,” but they are not necessarily “in-sync” if they are “in-phase.”

Colloquially, we tend to use the terms “in-phase” and “in-sync,” as if they are synonymous. Most of the time, doing so is no big deal. We generally know what each other means; but for answering the question,”Why is residential wiring known as single phase?” it is necessary to distinguish them.

First, I don't think you can factor out "1". You can simplify your inequality by simply dropping the "1", but you must leave the minus sign.

Second, the negative sign before a phasor functions as an operator which shifts the phase of the expression by 180 degrees. You cannot ignore this.

Third, V1 and V2 do NOT meet the criteria for in-phase waveforms. Their peaks do not coincide.

 

[mivey]

Sadly, my system kicks the photobucket.

I would be glad to email it to you if it would help.

The polarity of voltage is usually considered in relation to the direction of current flow.

Great. Do that with Besoeker's circuit. His currents are directed away from the neutral.

Since in an AC circuit the current alternates direction, the choice of Positive or Negative is arbitrary but should remain constant for the system being analyzed.

Once I picked it, I do not change it.

 

[rbalex]

The phase represents a location on the wave relative to a reference point. It does not "reset to zero" half-way through the cycle of the wave. Consider the use of the phasor diagram and how the angles vary from 0? to 360?.
...

Actually it effectively does "reset to zero" for sine and cosine; but, even if it didn't, it doesn't change the phase of the phenomena when they are "in-phase."; i.e., ω₁ = ω₂ and φ₁ = φ₂. And they damned well better be equal when you're considering the voltages on a "single-phase" transformer.

...We can track the change in the phase over time by plotting a vector that rotates from a reference axis. As the wave moves through the complete cycle, the phase changes from 0? to 360?. There is no "re-setting" of the phase angle when we reach the half-way point and I doubt you will find any valid text to support that claim. What I have stated is common knowledge and is found in any good textbook dealing with oscillating systems (at a minimum I know it is in my calculus textbooks, physics textbooks, and in my signals & systems textbooks. I have several of each in my library but can't get there now....

I suspect "...any good textbook dealing with oscillating systems ..." will essentially give a definition of phase very similar to the one rattus provided. That is, magnitude and polarity are irrelevant to defining phase. How the definition is applied in a given context may vary. You keep wanting to describe what a phase looks like rather than properly define what it is- and you are under no obligation to agree with my definition just recognize I'm using them consistently,

...
The positive and negative vectors point in opposite directions and their phase angle from the reference axis differs by 180?, not zero degrees. Cross two terminals with voltages having a 180? phase difference and you will find out quickly that they are not in phase but will get a quick lesson in interference between two waves that are not in phase.

You appear to be confusing phasors with phases; they sound alike but they are no more the same than "in-sync" or "in-phase."

 

[rattus]

FWIW IMHO, Technically speaking, according to the definition of "phase", two phases are available in a residential service. However, convention dictates that we call it single phase to avoid confusion with a real two phase system and because these two "phases" are usually provided by a single phase transformer fed by a single phase of a three phase system.

SINGLE PHASE IT IS!

Still, some will call L1 and L2 "phases" rather than "legs".

 

[rbalex]

First, I don't think you can factor out "1". You can simplify your inequality by simply dropping the "1", but you must leave the minus sign.

Second, the negative sign before a phasor functions as an operator which shifts the phase of the expression by 180 degrees. You cannot ignore this.

Third, V1 and V2 do NOT meet the criteria for in-phase waveforms. Their peaks do not coincide.

Com'on - even mivey didn't disagree with that one - it fundamental algebra. Where does "peak" show up in the definition of phase you provided - it isn't even implied.

 

[rbalex]

FWIW IMHO, Technically speaking, according to the definition of "phase", two phases are available in a residential service. However, convention dictates that we call it single phase to avoid confusion with a real two phase system and because these two "phases" are usually provided by a single phase transformer fed by a single phase of a three phase system.

SINGLE PHASE IT IS!

Still, some will call L1 and L2 "phases" rather than "legs".

Pure "Group 2" (Post 43)

 

[jim dungar]

Your statements continue to reflect the idea that there is only one real physical reference and that is from end to end across the winding. .

I have been using a consistent analysis. I have never said something must be, in fact I know I have said that I have personally used different models.

No. I had no interest in a parallel connection, only a series connection like we have in the residential transformer.

It would really help if you would read the entire question. I never asked if your graphic represented a parallel connection. I asked if it represented two re-connectable windings.

My position is that the reverse operation is also possible.

Read carefully next time. It sounds like you are arguing with my statement that both connections are possible.

The people who ask these questions have usually seen both voltage sets and are not digging around in the transformer windings.

Wow, and you slammed me for saying that 'what was seen on the scope was only an appearance'. Am I at fault for using a model that actually reflects the real connections?

From what I can gather, there are some that contend that the "out of phase" set does not really exist because they can not exist in the center-tap transformer windings (not saying that is your position). My graphic shows that they can, and do, exist in the center-tap transformer windings

Your graphic absolutely does not represent a standard transformer with a single primary winding and a single secondary winding, which was the basis of the OP. Instead it shows a center-tapped primary transformer feeding a single winding secondary.

Why do you find it so hard to say that the physical connections of devices do matter and they do result in a single actual answer?
Yes there are models that can be used to twist the answer into more usable formats, but they do not change the real world.

 

[mivey]

I have been using a consistent analysis. I have never said something must be, in fact I know I have said that I have personally used different models.

OK

It would really help if you would read the entire question. I never asked if your graphic represented a parallel connection. I asked if it represented two re-connectable windings.

Does it matter since I am only using it in a 120/240 configuration?

Read carefully next time. It sounds like you are arguing with my statement that both connections are possible.

Wow, and you slammed me for saying that 'what was seen on the scope was only an appearance'. Am I at fault for using a model that actually reflects the real connections?

Nope. Read carefully as I have said many times that either way is fine. Nothing wrong with using some physical feature to help you decide on a reference.

with a single primary winding and a single secondary winding, which was the basis of the OP. Instead it shows a center-tapped primary transformer feeding a single winding secondary.

Look again. On the right is a single-phase source on the two-wire primary side of the transformer. This powers the center-tapped secondary to the left. This center-tapped secondary is paralleled with the source from the left. The left and right sources parallel feed the resistive load.

Why do you find it so hard to say that the physical connections of devices do matter and they do result in a single actual answer?

A single answer for what? I thought above you said you were not stuck on there being only one answer.

Yes there are models that can be used to twist the answer into more usable formats, but they do not change the real world.

Do you not realize what you are calling the "real world" is a relative concept?

Do you not see that two voltages that are physically created to have a 180? phase difference can exist across the same center-tapped secondary windings on a transformer that has a single-phase source on the two-wire primary side? Does that not help you see that what you are calling the "real world" is based on relative reference frames?