Why is residential wiring known as single phase?

[jim dungar]

Jim, in order to answer the original question, we don't need to worry about the real world connections.

Of course we do. In my daily world of power systems, 'what really exisits' is extremely important everything else is simply math.

There is no doubt that we acn mathematically hadle the issue of -I, but could you demonstrate a real world source of negative current. I guess you could call -V a voltage drop, but I don't thnik I have ever seen an AC generator that actullly produces negative volts.

 

[rattus]

OK, piece by piece and more direct:

Do the currents have a characteristic function?

Do the current?s characteristic functions have a fundamental harmonic?

Do the fundamental harmonics of both voltages and currents have same the period P.

Is the fraction t/P of each fundamental harmonic of both voltages and currents identical throughout the period P?

Do you plan to keep evading the obvious?​

Now Bob, it is as plain as the nose on Pinocchio's face that the voltages differ in phase by PI radians. That is all there is to it! I am surprised that a PE can't or won't see that. Besides, we are arguing about the phases of the voltages, not the currents.

 

[Besoeker]

OK, piece by piece and more direct:

Do the currents have a characteristic function?

Do the current?s characteristic functions have a fundamental harmonic?

Do the fundamental harmonics of both voltages and currents have same the period P.

Is the fraction t/P of each fundamental harmonic of both voltages and currents identical throughout the period P?

Do you plan to keep evading the obvious?​

With respect, it's you engaging in obfuscation and you evading the obvious.

I'll state the obvious again for you.
Step by step.

In the configuration in post #1004, I_a and I_b are not in phase.
One starts at π/4, the other at 5π/5. They are clearly not in phase.
The load is resistive.
The the currents are not in phase simply because the voltages driving those currents are not in phase.
It's simple, obvious.
And irrefutable.

 

[rattus]

Of course we do. In my daily world of power systems, 'what really exisits' is extremely important everything else is simply math.

There is no doubt that we acn mathematically hadle the issue of -I, but could you demonstrate a real world source of negative current. I guess you could call -V a voltage drop, but I don't thnik I have ever seen an AC generator that actullly produces negative volts.

But Jim, this thread is NOT about your daily world. You clutter up the discussion when you insist upon talking ad nauseum about transformer connections. Experienced engineers, you included, journeymen too, already know those details, and whether the CT is a single terminal or two terminals strapped together doesn't matter.

Let me rephrase the OP's question:

Why is the split phase service which technically provides two *phases, called single phase?

*Phase is measured in radians.

My answer is:

Because a single transformer is utilized. Nuf sed!

BTW, AC generators do produce negative voltages, every half period.

Jim, you must have studied complex numbers and phasors. That is all it is. You represent RMS voltages and currents by magnitude and phase angle.

 

[rbalex]

With respect, it's you engaging in obfuscation and you evading the obvious.

I'll state the obvious again for you.
Step by step.

In the configuration in post #1004, I_a and I_b are not in phase.
One starts at π/4, the other at 5π/5. They are clearly not in phase.
The load is resistive.
The the currents are not in phase simply because the voltages driving those currents are not in phase.
It's simple, obvious.
And irrefutable.

Then answer the posed questions directly.

I'll repeat them:

Do the currents have a characteristic function?

Do the current?s characteristic functions have a fundamental harmonic?

Do the fundamental harmonics of both voltages and currents have same the period P.

Is the fraction t/P of each fundamental harmonic of both voltages and currents identical throughout the period P?

Do you plan to keep evading the obvious?​

 

[K8MHZ]

OP answered his own question

OP answered his own question

This is from post #29

"In electrical engineering, single-phase electric power refers to the distribution of alternating current electric power using a system in which all the voltages of the supply VARY IN UNISON. In contrast, in a three-phase system, the currents in each conductor reach their peak instantaneous values SEQUENTIALLY, NOT SIMULTANEOUSLY; in each cycle of the power frequency, first one, then the second, then the third current reaches its maximum value. The waveforms of the three supply conductors are offset from one another in time (delayed in phase) by one-third of their period."

So to clear all this up, the two AC voltages found in a house panel, though they be of opposing amplitudes, are referred to as single phase because their amplitudes VARY in unison. This will always be the case when voltages arise from the single transformer phase, regardles of how it is tapped. They will vary in unison.

Multiple phases only arise when amplitudes vary NOT in unison, but sequentially."

By far, the best post in this thread.

 

[mivey]

yes.

OK. So you should not take issue with windings being used in different directions both providing voltages that really exist.

In the case of the delta the windings are connected begining to end without changing the winding direction V43+V12. In the case of a wye, the end to end connection means one of the windings is physically rotated 180?, V43+V21.

Does not a physical rotation of a generator shaft produce a 180? voltage difference? Why would you think a physical change in a winding can't mean a 180? voltage difference?

Of course we do. In my daily world of power systems, 'what really exisits' is extremely important everything else is simply math.

If it is important, then why do you have an issue with the example I have given with the open wye that uses what really exists in the world of power systems?

To expand the terminal notation discussed before but now using center-tapped transformers:

 

[Besoeker]

Then answer the posed questions directly.

I'll repeat them:

Do the currents have a characteristic function?

Do the current’s characteristic functions have a fundamental harmonic?

Do the fundamental harmonics of both voltages and currents have same the period P.

Is the fraction t/P of each fundamental harmonic of both voltages and currents identical throughout the period P?

Do you plan to keep evading the obvious?​

I'm sure you know I know the answers to the questions.
I'm also sure you're trying to make a point by asking them.
So why not just make your point instead of faffing about?

 

[rattus]

Then answer the posed questions directly.

I'll repeat them:

Do the currents have a characteristic function?

Do the current?s characteristic functions have a fundamental harmonic?

Do the fundamental harmonics of both voltages and currents have same the period P.

Is the fraction t/P of each fundamental harmonic of both voltages and currents identical throughout the period P?

Do you plan to keep evading the obvious?​

Bob is trying to divert attention from the plain facts with his attempts to prove his erroneous claims with mathematical obfuscation. Bad form especially for a PE.

gar, mivey, bes, and I agree that Va and Vb are out of phase. That ought to tell you something. Maybe you should stop digging a hole before it falls in on you. Pinocchio's nose is growing!

 

[Besoeker]

gar, mivey, bes, and I agree that Va and Vb are out of phase.

I think Jim D also agreed that point.

 

[mivey]

...To expand the terminal notation discussed before but now using center-tapped transformers:

The "30?" in the last note should be "300?". I'll fix the typo in the graphic.

 

[mivey]

I think Jim D also agreed that point.

How so? He says the voltage outputs from the transformer must be in phase. Va and Vb are voltage outputs from the transformer so...

 

[jim dungar]

But Jim, this thread is NOT about your daily world. You clutter up the discussion when you insist upon talking ad nauseum about transformer connections. Experienced engineers, you included, journeymen too, already know those details, and whether the CT is a single terminal or two terminals strapped together doesn't matter.

WOW the real world somply clutters up the hteotetical.

Let me rephrase the OP's question:

Why is the split phase service which technically provides two *phases, called single phase?

*Phase is measured in radians.

Sure a little more obfuscation.
Single phase, antiphase and now split-phase.

My answer is: Because a single transformer is utilized. Nuf sed!

Wait a minute didn't you just say:

...transformer connections.

According to you, the answer does depends on transformer connections, so evidently you do not want to discuss the real answer.

 

[rbalex]

I'm sure you know I know the answers to the questions.
I'm also sure you're trying to make a point by asking them.
So why not just make you're point instead of faffing about?

No, I'm not so sure you know the answer is "yes" to all of them - well, maybe not the last one.



Do the currents have a characteristic function? : Yes.

Do the current’s characteristic functions have a fundamental harmonic? : Yes.

Do the fundamental harmonics of both voltages and currents have same the period P? : Yes

This is appears to be the sticking point. So let’s look at your diagrams more closely. I’m sure you recognize that the period of the resultant voltage across the resistor is the same. But you don’t seem to recognize that the time while either I_a or I_b are zero because they are clipped or rectified is still part of the period of their fundamental harmonic. In other words, the fundamental harmonics of both voltages and currents have same the period P.

​

Is the fraction t/P of each fundamental harmonic of both voltages and currents identical throughout the period P? : Yes – they have to be.

Therefore they all have the same phase.

We had already agreed that the current’s characteristics weren’t the basis for defining phase as it applies to conventional 120/240V systems anyway so I shouldn't have to deal with it; but I have been attempting to give you an “AH HA” moment.

Where polarity is a significant factor, the “a” and “b” voltages and currents are not synchronized. Where polarity isn’t significant, they all share the same phase.

Is it so difficult to recognize that, for any conventional 120/240V system, where any and every voltage you choose has the same phase, regardless of the method used to determine it, that it is reasonably called single-phase” based on the underlying mathematics. It certainly won’t diminish your competence, or even alter the way you design something. At worst, it only requires sacrificing the myth of the "osilloscope jungle" that, “We may call it that, but it really isn’t.”

I HATE FORMATTING WITH THIS SYSTEM!!!!!!

 

[jim dungar]

Who, other than you has made claims of non-existent voltages?

You did notice that the combined wiring diagram does have physical connections that are not the same as in the two individual ones don't you?
Open delta 5 is connected to 4, open wye 5 is connected to 1, combined 5 is connected to 3, 7, and 2.

Try your example again without physically reconnecting the transformers.

Try the V34 = -V43 argument by connecting a transformer with the windings actual reversed from each other.

 

[rattus]

WOW the real world somply clutters up the hteotetical.

Sure a little more obfuscation.
Single phase, antiphase and now split-phase.

Wait a minute didn't you just say: According to you, the answer does depends on transformer connections, so evidently you do not want to discuss the real answer.

No, it is endless talk about the real world, stuff we already know. We wouldn't have a split phase system if the transformers were not connected correctly. Surely you have heard the term before. Now, "antiphase" is a new term for me, but its meaning is obvious.

The real answer is "because there is only one transformer". Any reasonable person would assume it is properly connected.

 

[rattus]

Who, other than you has made claims of non-existent voltages?

You did notice that the combined wiring diagram does have physical connections that are not the same as in the two individual ones don't you?
Open delta 5 is connected to 4, open wye 5 is connected to 1, combined 5 is connected to 3, 7, and 2.

Try your example again without physically reconnecting the transformers.

Try the V34 = -V43 argument by connecting a transformer with the windings actual reversed from each other.

With all due respect, why are we discussing polyphase?

 

[Besoeker]

I?m sure you recognize that the period of the resultant voltage across the resistor is the same.

The duration, yes.
The timing, no.

 

[rbalex]

The duration, yes.
The timing, no.

HUH??? What does "timing" have to do with period? Your own diagram shows the period is from 0 to 360?

 

[gar]

120225-1248 EST

K8MHZ:

Your post 1366 references a definition in post 29.

The definition in 29 has logical problems. The continuity of the argument does not follow from the usage of the words used.

The quote from 29.

Ok great, that is actually the most lucid explanation I have seen for what ends up in a residential panel. What seems to be always missed though is this. You are saying that what originates as single phase is never going to somehow magically access the unconnected points at the transformer for additional phases. That the two legs in a house panel arise from a center tapping of the single phase of transformer winding and so are single phase, period.

But if the two legs in the house panel, as a result of this center tapping, exhibit AC voltages of opposing amplitudes in time, what is the difference? Isn't that what "phase" refers to? The propogation of a sine wave compared to an identical wave time-shifted so the amplitudes don't match?

NO, it isn't:

"In electrical engineering, single-phase electric power refers to the distribution of alternating current electric power using a system in which all the voltages of the supply VARY IN UNISON. In contrast, in a three-phase system, the currents in each conductor reach their peak instantaneous values SEQUENTIALLY, NOT SIMULTANEOUSLY; in each cycle of the power frequency, first one, then the second, then the third current reaches its maximum value. The waveforms of the three supply conductors are offset from one another in time (delayed in phase) by one-third of their period."

So to clear all this up, the two AC voltages found in a house panel, though they be of opposing amplitudes, are referred to as single phase because their amplitudes VARY in unison. This will always be the case when voltages arise from the single transformer phase, regardles of how it is tapped. They will vary in unison.

Multiple phases only arise when amplitudes vary NOT in unison, but sequentially.

What does unison mean. I have not found a definition that is usefully clear for use in post 29. But here is dictionary.com 's definition.

u?ni?son   /ˈyunəsən, -zən/ Show Spelled[yoo-nuh-suhn, -zuhn] Show IPA
noun
1. coincidence in pitch of two or more musical tones, voices, etc.
2. the musical interval of a perfect prime.
3. the performance of musical parts at the same pitch or at the octave.
4. a sounding together in octaves, especially of male and female voices or of higher and lower instruments of the same class.
5. a process in which all elements behave in the same way at the same time; simultaneous or synchronous parallel action: to march in unison.

So what is the meaning of

single-phase electric power refers to the distribution of alternating current electric power using a system in which all the voltages of the supply VARY IN UNISON.

Depends upon the meaning of unison. Does unison here mean that all voltages in the single phase system have identical zero crossing times, and at any other time have voltages that change in the same direction (polarity) and are proportional to one another. Or something else.

Then the next statement is

In contrast, in a three-phase system, the currents in each conductor reach their peak instantaneous values SEQUENTIALLY, NOT SIMULTANEOUSLY; in each cycle of the power frequency, first one, then the second, then the third current reaches its maximum value.

Now the subject is currents and not voltages. The work "peak" occurs. What does it mean. It should mean the most positive direction value unless otherwise modified, in other words peak alone would mean maximum, but here it may be being used to mean valley or minimum. I don't know. If we can substitute voltage for current and use peak to mean most positive, then this would argue in favor of the center tapped secondary having two output phases.

Next we get

Multiple phases only arise when amplitudes vary NOT in unison, but sequentially.

Why switch to amplitudes from voltages (currents). For that matter amplitudes of what? Voltage or current? This creates inconsistencies in the argument. I do not feel there is a good argument for basing the definition of phases on magnitudes vs instantaneous values.

In one part it references min and max, this does imply the possibility of a + or - sign. By normal convention something being more + is more max. And something more minimum is tending in the more negative direction.

From dictionary.com

max?i?mum   /ˈm?ksəməm/ Show Spelled [mak-suh-muhm] Show IPA noun, plural -mums, -ma  /-mə/ Show Spelled[-muh] Show IPA, adjective
noun
1. the greatest quantity or amount possible, assignable, allowable, etc.
2. the highest amount, value, or degree attained or recorded.
3. an upper limit allowed or allowable by law or regulation.
4. Mathematics .
a. Also called relative maximum, local maximum. the value of a function at a certain point in its domain, which is greater than or equal to the values at all other points in the immediate vicinity of the point. Compare absolute maximum.
b. the point in the domain at which a maximum occurs.
a

Note: greater means more positive.

On minimum from dictionary.com

min?i?mum   /ˈmɪnəməm/ Show Spelled [min-uh-muhm] Show IPA noun, plural -mums, -ma  /-mə/ Show Spelled[-muh] Show IPA, adjective
noun
1. the least quantity or amount possible, assignable, allowable, or the like.
2. the lowest speed permitted on a highway.
3. the lowest amount, value, or degree attained or recorded.
4. an arbitrary amount set by a restaurant, nightclub, etc., as the least amount to be charged each person for food and drink. Compare cover charge.
5. Mathematics .
a. Also called relative minimum, local minimum. the value of a function at a certain point in its domain, which is less than or equal to the values at all other points in the immediate vicinity of the point. Compare absolute minimum.
b. the point in the domain at which a minimum occurs.

in other words more negative.

Amplitude does not include or imply an association with + or -. From dictionary.com

am?pli?tude   /ˈ?mplɪˌtud, -ˌtyud/ Show Spelled[am-pli-tood, -tyood] Show IPA
noun
1. the state or quality of being ample, especially as to breadth or width; largeness; greatness of extent.
2. large or full measure; abundance; copiousness.
3. mental range, scope, or capacity.
4. Physics . the absolute value of the maximum displacement from a zero value during one period of an oscillation.
5. Electricity . the maximum deviation of an alternating current from its average value

What is wrong with mivey's definition? If a voltage source has two wires, then it is a single phase source. If a load has only two wires, then it is a single phase load. Extending this I believe you should conclude that a system with more than two source wires has the possibility of being a source of more than one phase.

.