Why is residential wiring known as single phase?

[jim dungar]

Of course you can connect the windings is series or parallel. The usual residential arrangement is in series.
You get tw0 120V supplies in anti-phase.
Without that that anti-phase, the circuit I presented in post #1004 couldn't work.
But it does.

Where have I connected anything in parallel? I just have 2 voltages referenced to neutral.
Are you saying that Vab is also important?

 

[rattus]

If you accepted what identity means mathematically, your question was answered in the quotation.


Nevertheless, I refer you Post 696 where I underlined all the complicated math terms and bracketed the phases of the trig identity. If you can make the emotional/intellectual leap to accept (? 180?) is a specific case of φ₀ rather than a general case of φ, and apply this to periodic Sine functions, then the phase of both equations is equal, in fact identically equal, and the sign is irrelevant.

Forget the identities, the phase angle for V1 is 0, for V2 it is 180 degrees. To be in phase, the phase angles must be equal. It really is that simple. Any attempt to change that fact through "reduction" is nonsense.

 

[rbalex]

Forget the identities, the phase angle for V1 is 0, for V2 it is 180 degrees. To be in phase, the phase angles must be equal. It really is that simple. Any attempt to change that fact through "reduction" is nonsense.

Who says?

 

[Besoeker]

Two different physical arrangements, two different waveforms.
Both have Van and Vbn as well as Van and Vnb. Why aren't both arrangements usable?

How about drawing the rectifier circuits that would suit the the circuit configurations you you presented in post #1092?
Then we can discuss their merits.

 

[mivey]

Chose a direction and use it consistently is not double-talk.
If you claim that the two winding outputs are 'in phase' when they are connected in parallel then you have chosen a direction for each output

In that configuration you are down to a two-wire circuit: one voltages, one current, one phase.

in the industry standard transformer connections I have been focussing on, the output of winding X1-X2 is in phase with the output of winding X3-X4. This is a simple fact.

And the output of winding X1-X2 is in phase with the output of winding X4-X3. This is also a simple fact.

All you have done is show how you can move your arbitrary reference point to produce two circuits that are out of phase, but you consistently ignore what really exists.

What really exists is that there are both in-phase and out-of-phase voltages at the output of the windings.

How does your math tell these two connections apart?Afterall Van=-Vna and Vnb=-Vbn

The signs, the angles, the subscripts...I would think that would be obvious.

Can either of these be used to feed Besoeker's rectifiers?

No.

Do the waveforms look the same?

No. One would not expect them to since the top has V_X4-X3+V_X2-X1 and the bottom has V_X3-X4+V_X2-X1

 

[mivey]

If we both agree to it, then a proper stipulation has been developed between us;

I don't see that happening. It is the whole approach about trying to call a phase something that it is not that I take issue with. I understand what you are trying to say, but I think your approach is wrong. There are other ways to skin that cat. Even so, you will eventually run into some of the same problems that exist with Jim's "line-to-line" method.

What it will eventually boil down to is that we call them what we call them because of convention and because the label fits some of what we see or fits the most common use. I promise you that any "rule-book" type attempt is going to be marred with exceptions. That is why I said if you are going to attempt some rule-play, Jim's method is much simpler and works for the majority of cases.

But for the record, I would prefer a definition that is consistent with the definitions, descriptions, examples, pictures, or whatever you want to call what our industry accepts as a common understanding. That understanding is consistent in all of the texts I reviewed before I quite because of the preponderance of the evidence (a couple of dozen or so?). Here is some wording that should be clear:

In-phase (AC waves): The condition in which AC waves are in step with with each other at all points such that all of the following are true:
1) the zero values of the waves occur at the same point in time
2) the maximums of the waves occur at the same point in time
3) the minimums of the waves occur at the same point in time
4) the ratios of the wave values at the non-zero points produce a positive number

 

[mivey]

Such silliness.

The center tap is obfuscation for Mivey and Besoeker.

Bottom line with only the two ends of the secondary coil A & B. They can dual trace +240V<0 in one direction and -240<180 in the other direction. Therefore AB is 180 degrees out of phase with BA.

After all, if Mivey can excuse referencing one direction when measuring AN and reversing direction then I can reverse my reference frame to measure BA to get the above.

Not quite. With a two-wire circuit (240 volts), you will only have one phase.

 

[jim dungar]

How about drawing the rectifier circuits that would suit the the circuit configurations you you presented in post #1092?
Then we can discuss their merits.

You called my second arrangement a parallel connection, but that could only be if the two outputs are identical, otherwise we would get 'fireworks' when we joined X1 joined to X3.
Two posts up Rattus is saying:

... the phase angle for V1 is 0, for V2 it is 180 degrees. To be in phase, the phase angles must be equal. It really is that simple.

Following his reasoning, if we assign V1 to the output of winding X1-X2 and V2 to the output of winding X3-X4, then my second arrangement can not be paralleled, therefore it is two separate voltages 180? apart from a common point which is what you claim to need for your circuits.

But you said that arrangement #2 will not work for you (by the way I concur), why not?

 

[mivey]

Where have I connected anything in parallel?

Agreed. They are still in series unless we join the ends. They are just not connected to provide 2*V in series.

 

[rbalex]

I don't see that happening. It is the whole approach about trying to call a phase something that it is not that I take issue with. I understand what you are trying to say, but I think your approach is wrong. There are other ways to skin that cat. Even so, you will eventually run into some of the same problems that exist with Jim's "line-to-line" method.

What it will eventually boil down to is that we call them what we call them because of convention and because the label fits some of what we see or fits the most common use. I promise you that any "rule-book" type attempt is going to be marred with exceptions. That is why I said if you are going to attempt some rule-play, Jim's method is much simpler and works for the majority of cases.

But for the record, I would prefer a definition that is consistent with the definitions, descriptions, examples, pictures, or whatever you want to call what our industry accepts as a common understanding. That understanding is consistent in all of the texts I reviewed before I quite because of the preponderance of the evidence (a couple of dozen or so?). Here is some wording that should be clear:

In-phase (AC waves): The condition in which AC waves are in step with with each other at all points such that all of the following are true:
1) the zero values of the waves occur at the same point in time
2) the maximums of the waves occur at the same point in time
3) the minimums of the waves occur at the same point in time
4) the ratios of the wave values at the non-zero points produce a positive number

Fundamentally, you are just resorting to Post 2. I've already said that's OK if you just wish to address it colloquially.

However, someone who wants to display their “superior” knowledge will eventually say "Yeah, we call it that; but it really isn't - here let me show you on my oscilloscope."

For the record you are still equating synchronism with phase, except you don’t require the amplitudes to be the same because you can adjust that on your oscilloscope with a scaling factor. I suggest you attempt to parallel a 120V single-phase generator with a 240V one that meets your four criteria for phase and you will get a very pragmatic lesson on the difference.

 

[rattus]

Who says?

I, for one, and mivey for two, and gar for three, and perhaps others

 

[rbalex]

I, for one, and mivey for two, and gar for three, and perhaps others

Perhaps; it just illustrates you can't tell the difference between your opinion and a definition either.

As far as I can tell, I haven't seen either of them jump to defend your statement. I doubt gar would say identities aren't relevant; he may not like the application, but they are valid. mivey might agree with you; but he's had several opportunities to say so.

 

[Besoeker]

But you said that arrangement #2 will not work for you (by the way I concur), why not?

What I posted is that it would not work for the rectifier arrangements I gave in this thread. Why not? That arrangement requires two voltages mutually displaced by 180deg.
And, if you have two voltages displaced by 180deg, they are not in phase.
And if you have two voltages that are not in phase........I'm sure you understand the inevitable conclusion.

 

[rattus]

Perhaps; it just illustrates you can't tell the difference between your opinion and a definition either.

As far as I can tell, I haven't seen either of them jump to defend your statement. I doubt gar would say identities aren't relevant; he may not like the application, but they are valid. mivey might agree with you; but he's had several opportunities to say so.

Mivey's position is well know, gar is in agreement with me, and Besoeker has just posted:

"And, if you have two voltages displaced by 180deg, they are not in phase."

All you have done with your identity is show that a sinusoid shifted by 180 degrees is equal to its inverse. Without the minus sign it would not be an inverse. So polarity is relevant.

Now look at the phasor diagram:

V2 = 120Vrms @ 180 <-----------N----------->V1 = 120Vrms @ 0

How can you say these two waves are in phase? You could go through the CRC Math Handbook and not find a way.

 

[pfalcon]

Not quite. With a two-wire circuit (240 volts), you will only have one phase.

With your own logic in play, try and prove it.

 

[pfalcon]

"And, if you have two voltages displaced by 180deg, they are not in phase."

All you have done with your identity is show that a sinusoid shifted by 180 degrees is equal to its inverse. Without the minus sign it would not be an inverse. So polarity is relevant.

Now look at the phasor diagram:

V2 = 120Vrms @ 180 <-----------N----------->V1 = 120Vrms @ 0

How can you say these two waves are in phase? You could go through the CRC Math Handbook and not find a way.

V2 to V1 = 240Vrms @ 180 ; V1 to V2 = 240Vms @ 0
See. I got two phases too!

 

[rattus]

V2 to V1 = 240Vrms @ 180 ; V1 to V2 = 240Vms @ 0
See. I got two phases too!

But you can only have one phase at a time; with a neutral you can have two phases at once. Still a single phase service though.

 

[jim dungar]

What I posted is that it would not work for the rectifier arrangements I gave in this thread. Why not? That arrangement requires two voltages mutually displaced by 180deg.
And, if you have two voltages displaced by 180deg, they are not in phase.
And if you have two voltages that are not in phase........I'm sure you understand the inevitable conclusion.

Mivey has previously said a series connection of two coils provides both in-phase and out-of-phase voltages, so what is wrong with the second arrangement. I used the voltages and angles Rattus suggested.
Except by looking at your oscilloscope how can you say my second arrangement will not work? Where is the math to show what does or doesn't work.


Rattus where did you get those voltages and angles, from the voltages across the individual windings or from the connection?

 

[rattus]

Rattus where did you get those voltages and angles, from the voltages across the individual windings or from the connection?

They are the voltages seen across the individual windings if we have two transformers connected X2 to X3 with that node being designated by "N". That is equivalent to a center tapped secondary.

 

[pfalcon]

But you can only have one phase at a time; with a neutral you can have two phases at once. Still a single phase service though.

That would be an opinion. I can wire circuits to make use of both the forward phase and the reverse phase. I can get six phases out of it with a neutral.