Why is residential wiring known as single phase?

[rbalex]

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.

At the very best, all you've done is accuse your colleagues in "oscilloscope-land" of refusing to accept that "single-phase" is indeed "single-phase." I don't know about the other three, but your head is apparently stuck so far up your oscilloscope, you can't tell the difference between synchronism and phase. I cautioned you a long time ago against letting a model color your understanding.

My last post to mivey has an alternate "real world" experiment that doesn't rely on an oscilloscope to illustrate the difference - you should try it, as well.

 

[rattus]

At the very best, all you've done is accuse your colleagues in "oscilloscope-land" of refusing to accept that "single-phase" is indeed "single-phase." I don't know about the other three, but your head is apparently stuck so far up your oscilloscope, you can't tell the difference between synchronism and phase. I cautioned you a long time ago against letting a model color your understanding.

My last post to mivey has an alternate "real world" experiment that doesn't rely on an oscilloscope to illustrate the difference - you should try it, as well.

''

Technically, according to the definitions of phase, we have two phases, but convention dictates that we say single phase--no argument there. And, I don't see how synchronism has anything to do with the issue.

You have yet to answer any of my questions in a direct manner. I would have expected better from a Professional Engineer.

 

[jim dungar]

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".

There is that nasty 'appearance' concept again.

Given the two unconnected windings, do they have an angle associated with their individual output voltages V1 and V2?

 

[Rick Christopherson]

Technically, according to the definitions of phase, we have two phases, but convention dictates that we say single phase--no argument there. And, I don't see how synchronism has anything to do with the issue.

You have yet to answer any of my questions in a direct manner. I would have expected better from a Professional Engineer.

There you go, just as I predicted you would do. You blew off the original contention, tried to deflect away from it, tried to trivialize it; so you could then continue to repeat it.

You do not technically have a phase shift. You have an inversion that you can mathematically represent as a phase shift. The physical action you took to go from V_n2 to V_2n is reversing polarity, which is an inversion, not a phase shift.

You didn't answer my original question. But then again, I've learned to not expect that from you.

 

[rattus]

There is that nasty 'appearance' concept again.

Given the two unconnected windings, do they have an angle associated with their individual output voltages V1 and V2?

You won't hear me using the term "apparent".

Yes, I had omitted the "n" for simplicity.

V1 = Vx1x2 = 120Vrms @ 0

V2 = Vx4x3 = 120Vrms @ 180

 

[ritelec]

Every sparky knows he's working with 2 phases in a standard residential panel, and better not get them mixed up! If I have to be careful with tandem breakers, and not getting my multi-wire legs on the same phase etc., how does "single phase" apply?

There are two ways to handle this.

For me I just accept 'because we do'

The other way takes 600 forum posts.

The "DEAD ANGELO FACTOR" ...whatever you think it's going to take....double it.


Coming up on 1200.......................:lol:

 

[rbalex]

''

Technically, according to the definitions of phase, we have two phases, but convention dictates that we say single phase--no argument there. And, I don't see how synchronism has anything to do with the issue.

You have yet to answer any of my questions in a direct manner. I would have expected better from a Professional Engineer.

I knew you would eventually get back to Post 2 as the "default"; it's the only rationale the ?oscilloscope - jungle ? can offer for refusing to accept that "technically" a "single-phase" system indeed has a "single-phase." The fact is there was a reason for calling it "single-phase" that predates oscilloscopes. Even the proper definition you originally offered confirms that. That's why you had to try to change it.

Since evading direct questions is your ?stock-in-trade?, it?s not too surprising you routinely accuse others of doing it. I have answered every one of your questions directly at least once - I've usually even referenced them for you. Originally, I thought your problem was math and reading comprehension; now I'm beginning to think reading retention is also in the mix.

 

[jim dungar]

You won't hear me using the term "apparent".

No you used the word 'seen'. Evidently that means something different to you then appear. Which thesaurus are you using?

Yes, I had omitted the "n" for simplicity.

V1 = Vx1x2 = 120Vrms @ 0

V2 = Vx4x3 = 120Vrms @ 180

If the windings are not interconnected, what are you using as your reference for the angles?
Based simply on the above angle assignments, doesn't the connection of X2&X4 provide 'two out of phase voltage with a common node'?

 

[rattus]

If the windings are not interconnected, what are you using as your reference for the angles?

Based simply on the above angle assignments, doesn't the connection of X2&X4 provide 'two out of phase voltages with a common node'?

First question: x2 and x3

Second question: No, draw polarity dots at x1 and x3, they are in phase. The common node is NOT a neutral.

 

[rattus]

There you go, just as I predicted you would do. You blew off the original contention, tried to deflect away from it, tried to trivialize it; so you could then continue to repeat it.

You do not technically have a phase shift. You have an inversion that you can mathematically represent as a phase shift. The physical action you took to go from V_n2 to V_2n is reversing polarity, which is an inversion, not a phase shift.

You didn't answer my original question. But then again, I've learned to not expect that from you.

The definitions of phase and phase difference make no distinction between a delayed or advanced wave and an inverted wave.

 

[pfalcon]

''
Technically, according to the definitions of phase, we have two phases, but convention dictates that we say single phase--no argument there. And, I don't see how synchronism has anything to do with the issue.
You have yet to answer any of my questions in a direct manner. I would have expected better from a Professional Engineer.

You have that backwards. Technically according to the definitions of phase you have ONE phase; but convention through use is to call them separate phases.
They only appear 180 out because you're measuring one leg in the direction of power flow and the second leg against power flow.

You don't have to have two legs to do that. You can use a dual trace and measure AB against BA. Instead of two |120|V phases that appear out you'll get two |240|V phases that appear out. It's the same principal each time except the physical probes overlap the section of coil being displayed.

Too bad we don't have peeps with quad trace scopes. Then they could display AB, AN, BA, BN all at the same time. Give it a shot. Try to create a proof that says AB, BA is only a single phase that doesn't prove AN, BN is single phase. Try to create a proof that AN, BN is two phases that doesn't prove AB, BA is two phases.

The target circuit is a simple ac circuit with a center-tap voltage divider. No more, no less.

BTW, by ANY definition let alone that of phase, it requires that there be two distinct separate entities to have two of something. AN, BN is nothing more than the left and right HALF of AB. A single solitary source of power.

 

[Besoeker]

so what is wrong with the second arrangement.
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.

There's nothing wrong with your second transformer arrangement. It just wouldn't work with the rectifier arrangements I've posted which need the positive half cycles to occur at different points in time.
Of course you could connect the windings as in your arrangement #2 and drive one or two full wave rectifiers.
My point with the half wave, two diode rectifier was to demonstrate that it required the two voltages to 180deg apart to produce the waveform gave.
If they are 180 deg apart, they can't be in phase. Not the same phase means there has to be more than one phase.
I'm sure you know all that.

 

[pfalcon]

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.

Tis NOT equivalent to a center tapped secondary. When you load a center tapped secondary you alter the power flow across the entire secondary. When you load two separate end-to-end transformers they don't affect each other the same way.

 

[pfalcon]

There's nothing wrong with your second transformer arrangement. It just wouldn't work with the rectifier arrangements I've posted which need the positive half cycles to occur at different points in time.
Of course you could connect the windings as in your arrangement #2 and drive one or two full wave rectifiers.
My point with the half wave, two diode rectifier was to demonstrate that it required the two voltages to 180deg apart to produce the waveform gave.
If they are 180 deg apart, they can't be in phase. Not the same phase means there has to be more than one phase.
I'm sure you know all that.

How about you build your rectifier out of two transformers 180 out then load one transformer with a substantial capacitive or inductive load ahead of the rectifier circuit?

 

[Besoeker]

How about you build your rectifier out of two transformers 180 out then load one transformer with a substantial capacitive or inductive load ahead of the rectifier circuit?

Draw what you want me to consider with numerical values and I'll consider it.
Seem fair?

 

[jim dungar]

First question: x2 and x3

I said they were unconnected, so you have arbitrally chosen reference points based on how you will physically be connecting them.

Second question: No, draw polarity dots at x1 and x3, they are in phase. The common node is NOT a neutral.

Now you are assigning their phase angles based on the physical construction of the windings, not on how they are connected.

How about a little consistency?

 

[ronaldrc]

Every sparky knows he's working with 2 phases in a standard residential panel

Are you sure, who have you been talking to?

http://forums.mikeholt.com/showthread.php?t=143211

 

[K8MHZ]

Are you sure, who have you been talking to?

http://forums.mikeholt.com/showthread.php?t=143211

Getting the OP to answer that could put us into and endless loop, looping back just ahead of the infamous Post #2, which, so far, has underestimated the outcome by about 50 percent.

Do we have enough bandwidth?

 

[rattus]

I knew you would eventually get back to Post 2 as the "default"; it's the only rationale the ?oscilloscope - jungle ? can offer for refusing to accept that "technically" a "single-phase" system indeed has a "single-phase." The fact is there was a reason for calling it "single-phase" that predates oscilloscopes. Even the proper definition you originally offered confirms that. That's why you had to try to change it.

Since evading direct questions is your ?stock-in-trade?, it?s not too surprising you routinely accuse others of doing it. I have answered every one of your questions directly at least once - I've usually even referenced them for you. Originally, I thought your problem was math and reading comprehension; now I'm beginning to think reading retention is also in the mix.

Firstly, you should show a little more respect for your elders.

Secondly, I ask you to answer this simple question, directly, no references to other posts, no condescending remarks, just the facts.

How can two diametrically opposed phasors be in phase?

 

[jim dungar]

There's nothing wrong with your second transformer arrangement. It just wouldn't work with the rectifier arrangements I've posted which need the positive half cycles to occur at different points in time.
Of course you could connect the windings as in your arrangement #2 and drive one or two full wave rectifiers.
My point with the half wave, two diode rectifier was to demonstrate that it required the two voltages to 180deg apart to produce the waveform gave.
If they are 180 deg apart, they can't be in phase. Not the same phase means there has to be more than one phase.
I'm sure you know all that.

Your specific half-wave rectifier works because AC current is bi-directional. One diode is connected to work in the forward direction, the other is connected to work in the reverse direction. Being able to connect those diodes in the manner of Van and Vbn while the windings are physically connected Van and Vnb, is certainly an advantage to you.