Why is residential wiring known as single phase?

[rbalex]

From IEEE Std 100 The IEEE Standard Dictionary of Electrical and Electronic Terms:

phase (of a periodic phenomenon ?(t), for a particular value of t) The fractional part t/P of the period P through which ? has advanced relative to an arbitrary origin.

Note: The origin is usually taken at the last previous passage through zero from the negative to the positive direction. See also: control system, feedback; simple sine-wave quantity. (IM) [120]

?(IM) [120]? indicates the definition was extracted from IEEE Std 120-1989. IEEE Master Test Guide for Electrical Measurements in Power Circuits.

I have been aware of this definition for a very long time, which is why I so readily (and quickly) accepted rattus'

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]

I was reluctant to use it because, when I have previously, too many fixate on the "note" rather than the definition; i.e., even though the definition clearly states "...an arbitrary origin," many thought the note demands the function to be identified by "...passage through zero from the negative to the positive." Rattus' definition didn't carry that baggage. Read carefully, the definition is silent on magnitude (amplitude) and sign (polarity).

 

[mivey]

No, the OP question concerns the voltage outputs of an actual center-tapped transformer, not of some 'black box' source.

The source on the right is not a "black box". It is a single-phase source. I can draw in a symbol of a generator between the two primary terminals if that would help you understand.

What is your 'real world' and how does it differ from my 'actual physical connections'?

You seem to have some idea that the polarity marks or terminal numbers or physical orientation of the primary or some other kind of pre-existing signpost dictate some kind of a "correct" reference that will dictate that there is only one "correct" answer.

Can you not see that I can have two sets of voltages (one with a 0? displacement and one with a 180?, both sets having their respective phase angles determined using the same physical rules) present across the same center-tapped winding at the same time? I assure you that no physical laws are being broken to make this happen as it is simply a physical fact.

A voltage must have a reference frame and that reference frame is not given by the physical connection. It may influence our choice of a reference frame but that is all.

Which one are they? Can Besoeker use the scope to determine which ones they are?
Your answer infers the actual connections affect the output.

The connection will determine if there are two voltages in series or two voltages in parallel. The connection will not tell us the location of the zero reference point or what direction is the positive direction.

So, it appears there is an actual industry accepted 'right way' to make a center tapped connection.

Never claimed otherwise. Are we still talking about the same thing? Are we talking about voltages or transformer connection diagrams?

 

[mivey]

Ummm, doesn't it take 2 reference points to determine any voltage? I would tend to think so. So regardless how you examine the system, you still have 3 reference points: A, B, & N

Do we call both of the terminals reference points or just one of the terminals? I was thinking "V12" was "voltage at 1 relative to 2" with terminal 2 being the reference. Also, when comparing "V5" to "V6" isn't the reference the terminal common to both?

 

[mivey]

If the parallel connection is X1-X2 and X3-x4, doesn't that mean winding X1-X2 and winding X3-X4 are 'in phase' with each other based on this specific construction?

They would have to be since you only have a two-wire circuit and only one voltage.

 

[jim dungar]

They would have to be since you only have a two-wire circuit and only one voltage.

So how do they become out of phase when they are connected in series. The sources creating the voltages do not change based on how they are connected. So if the sources of the voltages are in phase when they are connected in parallel how do they become out of phase when they are connected in series?

 

[jim dungar]

The connection will not tell us the location of the zero reference point or what direction is the positive direction.

I have never claimed it will. In fact I don't think I have ever tried to attached a specific direction other than per industry standard convention current flows 'out of' X1 when it "flows into' H1.

Never claimed otherwise. Are we still talking about the same thing? Are we talking about voltages or transformer connection diagrams?

You appear to be talking about voltages. I have consistently talked about transformer connections as the OP specifically addressed center-tapped transformers.

 

[jim dungar]

You seem to have some idea that the polarity marks or terminal numbers or physical orientation of the primary or some other kind of pre-existing signpost dictate some kind of a "correct" reference that will dictate that there is only one "correct" answer.

There must be a correct answer based on the physical connection.
There is not a correct direction, but there is a correct state of being in phase or out of phase based on the physical construction of the source, if not paralleling voltage sources would not be a big deal.

 

[mivey]

From IEEE Std 100 The IEEE Standard Dictionary of Electrical and Electronic Terms:
...

Note that it states "The fractional part t/P of the period P through which ? has advanced". It does not "reset" half way through like you propose.

... but I still know what phase means.

From some of the books in my library:

"Alternating Current Circuit Theory", Reed, 1956, pg 72

Note that the current and voltage are in phase, i.e., the sine waves representing them are zero at the same time and positive and negative together, and that the vectors representing these quantities coincide.

"Engineering Circuit Analysis", Hyatt, 1962, pg 269

Two sinusoidal waves that are to be compared in phase must both be written as sine waves, or both as cosine waves; both waves must be written with positive amplitudes; and each must be of the same frequency. It is also evident that multiples of 360? may be added to or subtracted from the argument of any sinusoidal function without changing the value of the function.

"Physics for Scientists and Engineers", Tipler, 2008, pg 458-459

The argument of the cosine function, ωt+δ, is called the phase of the motion, and the constant δ is called the phase constant, which equals the phase at t=0.
...
If we have two systems oscillating with the same frequency but different phases, we can choose δ=0 for one of them. The equations for the two systems are then
x₁=A₁cos(ωt)
and
x₂=A₂cos(ωt+δ)

If the phase difference δ is zero or an integer times 2Π, then the systems are said to be in phase. If the phase difference δ is Π or an interger times Π, then the systems are said to be 180? out of phase.

 

[mivey]

So how do they become out of phase when they are connected in series. The sources creating the voltages do not change based on how they are connected. So if the sources of the voltages are in phase when they are connected in parallel how do they become out of phase when they are connected in series?

Because you can choose a different reference frame.

But you would not necessairly have to change the reference frame. In the parallel configuration you could have the positive direction to be out of X3. In the series configuration you could still have the positive direction to be out of X3.

 

[mivey]

I have never claimed it will. In fact I don't think I have ever tried to attached a specific direction other than per industry standard convention current flows 'out of' X1 when it "flows into' H1.

Polarity deals with the instantaneous relationships between different parts of a circuit and is not the same thing as voltage direction. Remotely related, but not the same.

You appear to be talking about voltages. I have consistently talked about transformer connections as the OP specifically addressed center-tapped transformers.

Do you think people who question 120/240 systems having either one phase or mutiple phases are looking at the physical layout of the windings and having questions or looking at the voltages delivered and having questions? Anybody can see there is one transformer so how does that raise questions?

 

[mivey]

There must be a correct answer based on the physical connection.

But there is not just one answer because we can have more than one physical reference frame.

Do things age differently in orbit? It is not intuitve but it is true. A watch on Earth will physically show one amount of elasped time and a watch that went into orbit and back will show a different time. It is a physical fact but both watches are still correct. there does not always have to be one physically true answer as there can be multiple.

My graphic shows that both 0? displaced voltages and 180? voltages physically exist across the windings of the center tap transformer. Both are physical facts.

There is not a correct direction, but there is a correct state of being in phase or out of phase based on the physical construction of the source, if not paralleling voltage sources would not be a big deal.

That "state of being in phase" is based on a reference frame that is a choice, not a given. More than one reference frame is valid.

One way to put it simply: One reference frame says that two positive forces work together to produce a bigger force at the same time. The other reference frame says one positive force and one negative force work together to produce a bigger force at the same time.

Another way to look at it from a basic physics standpoint is that a rise in one direction is a fall in the other. The reference frame is a choice and that is a voltage fundamental.

 

[jim dungar]

But there is not just one answer because we can have more than one physical reference frame.

No there is not always more than one correct answer.

We are not discussing subatomic particles. String theory is not part of this topic. i have been focusing on real life, reach out and fondle them, electro-magnetic transformers.

The output of a single secondary winding of a transformer is dependent on the single primary winding. You can say the direction of the secondary is opposite that of the primary, you can say it is equal to the primary, you can say it is blue and the primary is water. But you cannot provide something from the 'Laws of Physics' that says the primary and secondary are not inter-dependent.

 

[T.M.Haja Sahib]

But, according to you, I do not understand the difference between a DC voltage and AC voltage.
It that were true, I'd not be fit to be called an engineer. Let alone marvelous. Yet, that's the charge you are laying at my door.
From anyone with reasonable knowledge and experience of electrical circuits, I'd have been chagrined to have been so charged.

With due respect,I said you are a marvelous engineer in the sense that you would dodge answering even simple questions such as posed in post#881.

 

[rbalex]

Note that it states "The fractional part t/P of the period P through which ƒ has advanced". It does not "reset" half way through like you propose.

From some of the books in my library:

"Alternating Current Circuit Theory", Reed, 1956, pg 72


"Engineering Circuit Analysis", Hyatt, 1962, pg 269


"Physics for Scientists and Engineers", Tipler, 2008, pg 458-459

Once again, per your MO, you assert something no one has said. I have asserted Sine or Cosine functions effectively “reset to zero” at the end of each period; they better, or your precious oscilloscope wouldn’t work no matter how many probes you used. I haven’t said they reset halfway; but they don't need to because the characteristic phase of the functions doesn’t change - anywhere in the period for that matter. (Amplitude and polarity are just irrelevant to defining phase)

Also per your MO, you simply released a new warren of rabbits by only citing examples; not definitions - even though the examples are, in fact, perfectly consistent with my definition of phase. (I don't require the functions to be of opposite polarity – I simply say they can be)

 

[mivey]

No there is not always more than one correct answer.

Not always. But neither is there always only one answer.

We are not discussing subatomic particles. String theory is not part of this topic. i have been focusing on real life, reach out and fondle them, electro-magnetic transformers.

No subatomic particles or string theory in my graphic either. Just an example of how there are two correct answers in this case.

The output of a single secondary winding of a transformer is dependent on the single primary winding. You can say the direction of the secondary is opposite that of the primary, you can say it is equal to the primary, you can say it is blue and the primary is water. But you cannot provide something from the 'Laws of Physics' that says the primary and secondary are not inter-dependent.

My graphic illustrates how you can have both 0? displaced voltages and 180? displaced voltages across the secondary windings. It does so without violating any "Laws of Physics".

 

[Besoeker]

Absolutely, when there are two windings on a single core, which is common for customer owned transformers. Utility transformers are usually center-tapped single winding units.

Good. A point of agreement which is refreshing.

Did you notice these windings can be connected either in parallel or in series?

Yes, and I already commented on that in post #879. If connected in parallel, you won't get 240V. And it isn't the usual residential wiring which is the topic of the thread.

If the parallel connection is X1-X2 and X3-x4, doesn't that mean winding X1-X2 and winding X3-X4 are 'in phase' with each other based on this specific construction?

No dispute about that. Normally, X2 gets connected to X3 giving the equivalent of a centre-tapped arrangement. To hots, say V1 and V2, and one neutral N.
Neutral in this arrangement is the common. Resulting in V_1n and V_2n being mutually displaced by 180 degrees. They cross zero at the same time. They are in anti-phase. Not in phase. If they are not in phase it is difficult to construe that as single phase. It's pretty much the same logic that gets a hexaphase circuit from three phase.

 

[Besoeker]

With due respect,I said you are a marvelous engineer in the sense that you would dodge answering even simple questions such as posed in post#881.

Actually, old son, you called me marvelous before you posed that question.
Anyway, mivey already answered it and I don't disagree with that answer and I see no sense in repeating it.
The one thing I might add is that appending a polarity sign to an alternating quantity, as you did, doesn't make a lot of sense.

 

[Besoeker]

Several folks have attempted to show me my error by demonstrating in various unnecessary and often highly complex ways, what essentially boils down to:[/SIZE]
a ≠-a
Of course, that?s true.

Provided of course:
a ≠ 0

 

[T.M.Haja Sahib]

Anyway, mivey already answered it and I don't disagree with that answer and I see no sense in repeating it.
The one thing I might add is that appending a polarity sign to an alternating quantity, as you did, doesn't make a lot of sense.

mivey answered without regard to numerical quantities mentioned under the heading DC and AC and you do not want to attach any meaning to the numerical values under the head AC.
Why can't you make an attempt in interpreting the voltage values under the heads AC and DC and share your marvelous knowledge on it with us?

 

[mivey]

Once again, per your MO, you assert something no one has said. I have asserted Sine or Cosine functions effectively ?reset to zero? at the end of each period; they better, or your precious oscilloscope wouldn?t work no matter how many probes you used. I haven?t said they reset halfway; but they don't need to because the characteristic phase of the functions doesn?t change - anywhere in the period for that matter. (Amplitude and polarity are just irrelevant to defining phase)

Something YOU have made up that is not supported by the references you have cited.

Also per your MO, you simply released a new warren of rabbits by only citing examples; not definitions - even though the examples are, in fact, perfectly consistent with my definition of phase. (I don't require the functions to be of opposite polarity ? I simply say they can be)

As per your MO, continue to spin and ignore the facts. The textbooks do not agree with your made-up theories. You are so enamoured with the flotsom you have created that you will continue to hang on to it at any costs.

Here are some more for you:

"Polyphase Currents", Still, pg 8

Phase difference. - Two alternating E.M.F.s of the same chartacter and periodicity, or an alternating current and the E.M.F. to which it owes its existence are said to be in phase when the growth and decrease, reversal, and maximum values (of the same sign) occur simultaneously

"Handbook for Electrical Engineers", Pender, pg 15

Currents and Voltages in Phase, in Quadrature and in Opposition.-When the phase difference is zero the current and potential drop are said to be "in phase"; when the phase difference is П/2 radians or 90? the current and potential drop are said to be "in quadrature"; when the phase difference is П radians or 180? the current and potential drop are said to be "in opposition."

So keep on spinning and living in the dream world you have created.