Why is residential wiring known as single phase?

[petersonra]

188 pages?

 

[rbalex]

120307-1120 EST

If leg A to neutral and leg B to neutral were "in-phase" and of equal magnitude, then you could put the shorting bar between them. That is what you do when you parallel generators. But if they are not "in-phase" then there will be a large current, and obviously you would not short those terminals together.

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Yes - so? I thought we were discussing conventional 120/240V systems.

 

[rbalex]

Vbn=-Vnb

sin(wt+180)=-sin(wt+0): no dropped phis

So do you mean that -sin(wt+0) is not equal to -sin (wt)?

Or do you mean that -sin(wt+0) is not equal to sin(wt-180)?

If he hasn't already; he will tell you that wt+180 isn't equal to wt+0. He just doesn't understand indiscriminate swapping in and out of the Sine argument is invalid.

 

[rattus]

Vbn=-Vnb

sin(wt+180)=-sin(wt+0): no dropped phis

So do you mean that -sin(wt+0) is not equal to -sin (wt)?

Or do you mean that -sin(wt+0) is not equal to sin(wt-180)?

Not at all Jim. I simply mean that the phase of -sin(wt) is NOT (wt). It is (wt + PI) which is apparent from the equivalent expression, sin(wt + PI).

You cannot dump the phase constant through tricky trig or any other subterfuge. That's all. This notion cannot be supported in any textbook or any reference because it is simply false!

 

[rattus]

If he hasn't already; he will tell you that wt+180 isn't equal to wt+0. He just doesn't understand indiscriminate swapping in and out of the Sine argument is invalid.

I can answer for myself Bob!

 

[gar]

120307-12259 EST

Yes the discussion is about 120/240 systems. That does not mean in a discussion you exclude a description that will show the failure a given theory. My shorting bar shows that the leg A and leg B voltages to neutral are not "in-phase".

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[rbalex]

I can answer for myself Bob!

Yes you can. I apologize for that. So you will stop speaking for me too - right?

 

[pfalcon]

Nonsense. There are TWO phases present, nothing mythical about it. We have long agreed though that the TWO phases are obtained by center tapping the transformer--the split phase system--and this system is known as a single phase system.

Mythical isn't exactly the right word here. By definition (1) there is one and only one phase. By definition (2) there are six phases present V_an, V_na, V_bn, V_nb, V_ab, V_ba.
They're all real, they're all usable. But the definitions are not interchangeable.

All voltages in the split phase system do not carry the same phase. In other words, the phase of
sin(wt + phi) is NOT wt except for the trivial case!
And, we CANNOT dump phi with tricky trig!

It's not tricky trig. It's using definition (1) instead of definition (2). Physically there's nothing split about the 120/240V system. Its a 240V center tapped voltage divider. Electrically (in consistence with definition 1) there is a single phase that runs from A to B. As such there is directionality to measurements. As such when you reverse your leads you have to invert the measured polarity of the voltage.

Practical usage on the other hand tends to utilize definition (2) instead. Consistent with definition (1) we would wire a house with V_an and V_nb with independent wiring. But we save an extra wire by using V_an and V_bn. Cheaper. But in doing so we have to use definition (2) or we burn the house down.

AC is very much like a teeter-totter. There is only one board on the teeter-totter (single plank)(def 1). But if you're on the ground walking laps around it, you have to alternate which side you step under or you get bonked on the head (2 seats)(def 2) hence a 1/2 cycle out-of-phase from end to end.

Unfortunately with phase we have only a single overloaded word whereas with a teeter-totter we can refer to the plank or the seats.

 

[rbalex]

120307-12259 EST

Yes the discussion is about 120/240 systems. That does not mean in a discussion you exclude a description that will show the failure a given theory. My shorting bar shows that the leg A and leg B voltages to neutral are not "in-phase".

.

Yes - so? I thought we already dismissed "in phase" and phase as being synonymous long ago. They are no more the same as phase and phasor - even if they sound alike.

Otherwise, you're imposing a definition that hasn't been generally accepted by both sides. If others have, they can deal with it; I haven't. If you want to say that is your definition, that is actually fine; but it doesn't obligate anyone else to accept it. This is why definitions need to be agreed upon early in such a discussion.

 

[pfalcon]

120307-12259 EST
Yes the discussion is about 120/240 systems. That does not mean in a discussion you exclude a description that will show the failure a given theory. My shorting bar shows that the leg A and leg B voltages to neutral are not "in-phase".
.

Actually no. All it demonstrates is that the secondary coil has a potential from end to end. Which it must or you wouldn't be reading any voltage at all on either end.

The issue again goes back to "It's called one phase because there is one and only one voltage gradient being driven from A to B." Your example of putting two independent generators side by side in parallel would actually be two matched single phase coils. Not one phase; but two phases that are matched. (definition 1)

But YOU (and several others) are intent on using definition (2). The timing of voltages as though they were independent. They're not independent; as they're the opposite end of the same phase that creates the potential difference in the first place. But if you're wiring and don't treat them as independent, then you'll get bonked on the head. So by (2) you have more than 1 phase, which is not just acceptable but conventional in wiring houses. It also has nothing to do with the OP.

 

[Besoeker]

Hopefully to you - you said you couldn't read the original.

No. I said it was difficult to read when providing a response because of all the tags/

Only if you include line-to-line voltages; not if you only consider line-to-neutral voltages - then there are only three phases.

Sorry chum.
Six phases, all line to neutral.

1. Vmsin(ωt)
2. Vmsin(ωt+π/3)
3. Vmsin(ωt+2π/3)
4. Vmsin(ωt+π)
5. Vmsin(ωt+4π/3)
6. Vmsin(ωt+5π/3)

 

[rattus]

Yes - so? I thought we already dismissed "in phase" and phase as being synonymous long ago. They are no more the same as phase and phasor - even if they sound alike.

Otherwise, you're imposing a definition that hasn't been generally accepted by both sides. If others have, they can deal with it; I haven't. If you want to say that is your definition, that is actually fine; but it doesn't obligate anyone else to accept it. This is why definitions need to be agreed upon early in such a discussion.

I believe that I have shown that 'in phase' means that the 'phases' are equal. In other words,

wt + phi1 = wt + ph2 where phi1 and phi2 are the starting points of the two waves,
or
ph1 = phi2

If you can't accept this informal description, that means your mind is closed.

 

[rbalex]

No. I said it was difficult to read when providing a response because of all the tags/


Sorry chum.
Six phases, all line to neutral.

1. Vmsin(ωt)
2. Vmsin(ωt+π/3)
3. Vmsin(ωt+2π/3)
4. Vmsin(ωt+π)
5. Vmsin(ωt+4π/3)
6. Vmsin(ωt+5π/3)

So:
Vmsin(ωt+π) = - Vmsin(ωt) and
Vmsin(ωt+4π/3) = -Vmsin(ωt+π/3) and
Vmsin(ωt+5π/3) = -Vmsin(ωt+2π/3)

is false?

 

[rbalex]

I have actual "real world" work to do, but I haven't abandoned the discussion.

 

[Besoeker]

So:
Vmsin(ωt+π) = - Vmsin(ωt) and
Vmsin(ωt+4π/3) = -Vmsin(ωt+π/3) and
Vmsin(ωt+5π/3) = -Vmsin(ωt+2π/3)

is false?

No.
So what?
I gave you six different voltages.
I can express any one of them in terms of any other.
That doesn't alter the simple fact that there are six of them.

 

[Rick Christopherson]

No.
So what?
I gave you six different voltages.
I can express any one of them in terms of any other.
That doesn't alter the simple fact that there are six of them.

And I can give you six voltages for a 3-phase wye system. Does that make it hexaphase also?

 

[rbalex]

No.
So what?
I gave you six different voltages.
I can express any one of them in terms of any other.
That doesn't alter the simple fact that there are six of them.

Yes - so, I showed you that all six can be written in terms of three identical phases - your "hexiphase" system is just a glorified three-phase system. Or are you claiming that every time you can find a different way of expressing a voltage function - a new phase appears?

 

[rbalex]

Yes - so, I showed you that all six can be written in terms of three identical phases - your "hexiphase" system is just a glorified three-phase system. Or are you claiming that every time you can find a different way of expressing a voltage function - a new phase appears?

I should have said "three identical pairs of phases" - but you knew what I meant didn't you? Unless you are mining for objections, of course.

 

[rattus]

The Smartest Man I Know:

The Smartest Man I Know:

Just talked with the smartest man I know. He says in so many words that you CANNOT use trig identities to dump the phase constant!

 

[Besoeker]

I should have said "three identical pairs of phases" - but you knew what I meant didn't you? Unless you are mining for objections, of course.

Six different expressions...........
Different is not identical.