Why is residential wiring known as single phase?

[Besoeker]

Request for some more doing with your scope.

Use X-Y mode in the scope to obtain Lissajous figure for 0 degree phase difference.Connect V1n to X leads and Vn2 to Y leads.What do you observe in the screen of your scope?

That would be a daft thing to try for reasons I already explained.

 

[T.M.Haja Sahib]

That would be a daft thing to try for reasons I already explained.

See the link below.
http://en.wikipedia.org/wiki/File:Lissajous_figures_on_oscilloscope_(90_degrees_phase_shift).gif

 

[Besoeker]

Request for some more doing with your scope.

Use X-Y mode in the scope to obtain Lissajous figure for 0 degree phase difference.Connect V1n to X leads and Vn2 to Y leads.What do you observe in the screen of your scope?

See the link below.
http://en.wikipedia.org/wiki/File:Lissajous_figures_on_oscilloscope_(90_degrees_phase_shift).gif

That shows measurements of to voltages wrt a common point.
Which is what I showed in #404.
And not what you requested in #700.

 

[T.M.Haja Sahib]

That shows measurements of to voltages wrt a common point.
Which is what I showed in #404.
And not what you requested in #700.

Please note that you measured voltages V1n and V2n with respect to time in post#404.But what I requested in post # 700 is to display the phase relationship between voltages V1n and Vn2 in the form of a Lissajous figure directly in your scope using its X-Y mode.Got it?

 

[Besoeker]

Please note that you measured voltages V1n and V2n with respect to time in post#404.But what I requested in post # 700 is to display the phase relationship between voltages V1n and Vn2 in the form of a Lissajous figure directly in your scope using its X-Y mode.Got it?

I'm afraid you didn't "got it"
Look at the connections of both scope lead ground leads in the link you posted. Notice something?
They are both connected to ground. The signals being measured are voltages with respect to common point.
What you're asking for is to connect the two scope grounds to different potentials. And that would be daft.
But, I have explained all this before.

 

[T.M.Haja Sahib]

I'm afraid you didn't "got it"
Look at the connections of both scope lead ground leads in the link you posted. Notice something?
They are both connected to ground. The signals being measured are voltages with respect to common point.
What you're asking for is to connect the two scope grounds to different potentials. And that would be daft.
But, I have explained all this before.

No. Connect 'n' to the common.V1 to X and V2 to Y.

 

[Besoeker]

No. Connect 'n' to the common.V1 to X and V2 to Y.

Which is how I connected the probes in #404.
And not what you requested in #700 assuming you gave the subscripts (V1n and Vn2) in the order you intended.
And thus something you can't do as I've already explained several times.

 

[T.M.Haja Sahib]

Which is how I connected the probes in #404.
And not what you requested in #700 assuming you gave the subscripts in the order you intended.
And thus something you can't do as I've already explained several times.

Sorry,but you do not understand.If you made use of X-Y mode of operation in your scope,you would not see regular sine waves but entirely different shapes called 'Lissajous figures.These 'Lissajous figures'bear a constant relationship to the phase difference between the two sine waves applied to X-Y.For example,the Lissajous figure for two sine waves with a phase difference 90 degree is a circle.See link in post#702.
Please proceed now using X-Y mode in your scope.Will you to bring this thread to an end?

 

[Besoeker]

Sorry,but you do not understand.

Unkind and untrue.
The boot is on the other foot.
You simply cannot connect the the grounds of the two scope probes to different potentials as you have suggested in post #700.
It matters not a whit whether the scope is in Y-T or X-Y mode.
The scope BNC inputs are the same for both. It is simply a change of function for how the data is displayed.

Please proceed now using X-Y mode in your scope.

And risk knackering my scope by using one input connected as V1n and the other as Vn2? No thanks.

 

[T.M.Haja Sahib]

Unkind and untrue.
The boot is on the other foot.
You simply cannot connect the the grounds of the two scope probes to different potentials as you have suggested in post #700.
It matters not a whit whether the scope is in Y-T or X-Y mode.
The scope BNC inputs are the same for both. It is simply a change of function for how the data is displayed.


And risk knackering my scope by using one input connected as V1n and the other as Vn2? No thanks.

I am repeatedly telling (in post #700 also)to connect common 'n' to common grounds of two inputs.How it will risk knackering your scope?
The wave shapes you obtained earlier were on time base.But this time,the time base would be bypassed and you will see a different phase relationship between the two voltages.

 

[pfalcon]

Sorry, thought I was clear. The premise that the physical location of the voltage reference must also coincide with the physical location of the other voltage is the fundamental fault. That is not the case and anyone who has ever made a phasor diagram should know this. It might also be worth mentioning, as I have in the past, that a phasor diagram and circuit diagram are not the same thing either so you should see the disconnect between the physical layout and the related physical angles vs the voltage phasors with the related phasor angles.

See here:

Photobucket is blocked here so no picture.

Okay, those statements are clear. However... The reference frame I suggested is not a voltage reference, nor a phasor diagram, nor a circuit diagram. It's a phase reference frame. And the frame was chosen for two specific reasons: 1) It minimizes measurement errors ; 2) It's inclusive.

Without seeing it, I suspect you have an application specific phasor diagram. It'll happily work for all your intended purposes. An issue I thought we had previously resolved. If all you care about is your intended purpose then what you have is more than enough. All the results will be usable.

But the bottom line of what we are really looking at (as opposed to how we can manipulate it) is that we have a 240Vac Single-phase voltage divided circuit with a mid-point reference. So it's called single-phase because that's what it is.

The typical argument in this thread has been: Because I can hook up like this, see it like this, use it like this, mathematically describe it like this, then it isn't anything else but this.

Except, yes it is something else. Something else with properties that allow you to do what you want to do. To the best of my knowledge, barring a few typographical errors, I don't know of anyone that has made any false postings.

It can be displayed on an oscilloscope in numerous different ways. Just because we ground the neutral, which makes it the most logical and convenient place to reference, doesn't make that the definitive reference. All the other reference points are just as valid. All the other reference points show graphs that are just as real, just as accurate, just as correct. And most of those graphs show sections of the secondary coil to have <0 or <180 depending on whether your hot probe is left or right of the reference probe. A fact that ought to intuitively tell you that the direction you place your probe matters to the display and not the circuit. And yet...

 

[Besoeker]

I am repeatedly telling (in post #700 also)to connect common 'n' to common grounds of two inputs.

But not what you requested in #700 assuming you gave the subscripts (V1n and Vn2) in the order you intended.

The wave shapes you obtained earlier were on time base.

I'm well aware of that. But whether the voltages are displayed in Y-T format or X-Y format is irrelevant to the simple point that you cannot connect the probes in the way that you have asked in post #700.
If you want to look at the two voltages of the 120-0-120 system simultaneously, as indeed you would need to do to determine their phase relationship, the only way to connect the probes and not cause damage is as I did for post #404.
That is V1n and V2n.
Not V1n and Vn2.
Regardless of display mode.

 

[jim dungar]

The premise that the physical location of the voltage reference must also coincide with the physical location of the other voltage is the fundamental fault.

I know it has been a lot of posts, but did I miss where someone said the reference must be based on the physical, except for the group talking about the physical connection of an oscilloscope?

 

[gar]

120213-0830 EST

Besoeker, T.M., and others:

In post 501 I discussed scopes and Lissajous figures. To eliminate the ground problem I described the signals to the deflection plates. This eliminates the common connection problem. But this can also be solved by using differential inputs to the scope channels.

The important point about the Lissajous figures is that they allow seeing the phase relationship of the X and Y signals. Also if the frequencies have exact ratios defined by integers, then stable patterns are displayed.

For a 1/1 frequency ratio and equal amplitudes the Lissajous figure is a straight line at 45 deg from left to right. 0 deg being horizontal. Positive angles on the scope face are in the counterclockwise direction. As the phase of one input relative to the other is shifted the curve expands to an ellipse, to a circle (at an electrical phase shift of 90 deg), back to an ellipse, and then to a straight line at 135 deg when the electrical phase shift is 180 deg.

The major axis stays at 45 deg until the electrical phase shift is 90 deg. After this increasing the electrical phase shift puts the major axis at 135 deg until the electrical phase shift is 180 deg.

The angle of the Lissajous figure moves from 45 deg on the scope at 0 electrical phase shift to 135 deg on the scope from an electrical 180 deg phase shift. Continuing the electrical phase shift toward 360 deg the figure becomes a circle at an electrical phase shift of 270 deg, and at 360 deg of electrical phase shift a straight line at 225 deg or ( 45 deg).

See:
http://en.wikipedia.org/wiki/Lissajous_curve

The following is a real neat site where you can play with any desired combinations.
Checkmark FRONT, change to 8 and 8 Hz, and whatever phase shift you want, then click START. Press STOP and change values, then START again.
http://ngsir.netfirms.com/englishhtm/Lissajous.htm

.

 

[mivey]

The phase of the reduced function is still [ω t + φ₀]

It is no such thing because you have shifted the phase. You are just making this up as you go. That is not how phase is defined and you are ignoring the initial conditions. The link you keep referencing does not say what you are saying either. Any good physics text or calculus text will show that. I have several in my library and can get you some references when I get back but you should be able to find these on your own. Besides, you should know better anyway but I understand that things can be forgotten over time. How about you crack open some of your old college texts and have a look?

Unless you that insist sign is an element of the definition of phase (which I acknowledge many erroneously have)...

Erroneous according to you. You have no mathematical basis for this theory of yours as you have just made it up. Neither the physics nor the math support what you are claiming.

...my math is not even particularly difficult, let alone "new."

The Trig is not new but what is new is your re-defining phase constants such that they can be different but equal.

Please forgive me, I thought I had already discussed your spring analogy with you before.

Yes, I do beleive they are in phase; I don't beleive they are in synchronysim. Certainly things that ae synchronized are in phase, but the reverse isn?t necessarily true. I find it intertesting that some of the debaters are willing to give up amplitude,('cause their scope and scaling factors says so) but insist polarity is a requirement of phase.

I find it interesting that you just make these things up with no factual or sound mathematical basis. I'm pretty sure I could use Euler's identities to extract any portion of the phase constant I want and declare that the revised number is now the real "phase constant". That is what you are claiming and it just is not so.


In considering the physical system:

You can have an oscillating source drive one large output to the right or to the left. You can also have it drive two smaller outputs to the right, two smaller outputs to the left, or one small output to the left plus one small output to the right.

The fact that the source parts may or may not be coupled together is not what I am focused on. For the single-phase transformer, the source parts are coupled together and the forces are in phase. My position is that the single coupled source can also provide a set of outputs that are opposite in phase. This would be the same outputs you can get from source parts that are physically opposite in phase but can also be coupled together to work in phase.

Looking at the outputs instead of the source configuration makes it obvious that the coupled source, whether it is made of 0? displaced parts or 180? displaced parts is capable of delivering either two outputs with a 0? displacement or two outputs with a 180? displacement. Whether or not you want to call these phase differences is a matter of definition preference. If you use the technically correct definition of phase you can have two phases present at the output and a load that requires two phases with a 180? displacement can be served by the single-phase center-tapped transformer.

To try to use the fact that the source is single-phase, and to try to redefine the physics or try to redefine the math to force a fit to a label that is limited in scope does not make sense. The voltages are what they are where they are.

A ?180? phase displacement doesn't result in different phase,(i.e.,wt is still the same) unless you insist sign (or polarity) is necessary to define phase.

The physics and the math both show you are wrong and further support the fact that you are just making this up.

 

[mivey]

I know it has been a lot of posts, but did I miss where someone said the reference must be based on the physical, except for the group talking about the physical connection of an oscilloscope?

Yes, you missed it. That was pfalcon's premise.

 

[mivey]

...1) It minimizes measurement errors

Maybe

...2) It's inclusive.

Unsubstantiated

So it's called single-phase because that's what it is.

Of course it is single-phase. But it is capable of delivering two phases displaced by 180?. We don't use the name "two-phase" for those two phases because by convention we reserve that name for a quadrature phase system. That does not mean that the two phases do not exist.

The typical argument in this thread has been: Because I can hook up like this, see it like this, use it like this, mathematically describe it like this, then it isn't anything else but this.

Except, yes it is something else. Something else with properties that allow you to do what you want to do. To the best of my knowledge, barring a few typographical errors, I don't know of anyone that has made any false postings.

I seem to read that some think the two 180? displaced phases do not exist because they are not really displaced. That is what I take issue with. I contend that both voltage output options exist and are usable as such and that the displacement really does exist.

Just because we ground the neutral, which makes it the most logical and convenient place to reference, doesn't make that the definitive reference.

Of course not. It is just one of several choices we can make.

... All the other reference points are just as valid. All the other reference points show graphs that are just as real, just as accurate, just as correct. And most of those graphs show sections of the secondary coil to have <0 or <180 depending on whether your hot probe is left or right of the reference probe. A fact that ought to intuitively tell you that the direction you place your probe matters to the display and not the circuit. And yet...

While most circuits don't care, it does matter to some circuits.

 

[rattus]

Sorry, but there's no reason to loose the generality. You have simply identifed the special case where φ₀ = 0. So:

V1n = 170(sin(wt))
V2n = 170(sin(wt +/- 180)) = -170(sin(wt))

A ?180? phase displacement doesn't result in different phase,(i.e.,wt is still the same) unless you insist sign (or polarity) is necessary to define phase.

Alright, then let phi0 be zero. Now the phases of the V1 and V2 are:

phi1 = (wt)

phi2 = (wt +/- 180)

They are clearly not equal. The angular positions of the two waves are not the same. We have a phase displacement or phase shift. They are out of phase. You have shown V2 is the negative of V1 but that does not prove your point.

Maybe there is something I missed. Tell me if I am wrong.

 

[T.M.Haja Sahib]

But not what you requested in #700 assuming you gave the subscripts (V1n and Vn2) in the order you intended.

I'm well aware of that. But whether the voltages are displayed in Y-T format or X-Y format is irrelevant to the simple point that you cannot connect the probes in the way that you have asked in post #700.
If you want to look at the two voltages of the 120-0-120 system simultaneously, as indeed you would need to do to determine their phase relationship, the only way to connect the probes and not cause damage is as I did for post #404.
That is V1n and V2n.
Not V1n and Vn2.
Regardless of display mode.

gar
I request your comments for above with respect to your post #714

 

[rbalex]

It is no such thing because you have shifted the phase...

I have reduced a periodic function - properly. Either you don't understand that or you simply refuse to accept mathematically valid substitutions because you don't like them.