Why is residential wiring known as single phase?

[Besoeker]

I would, if there was a snowball's chance in heck of you suddenly becoming open-minded.

Try it.
What have you got to lose?
I'm not immune to admitting being wrong or not knowing something.
I have prefaced a few post by declaring myself an ignorant Brit.
Not that I'd advise you to call anyone ignorant - just making the point that I'm up front about not knowing something.

 

[T.M.Haja Sahib]

V_msin(ωt) and V_msin(ωt+π) are not in phase.

But load voltages are.

 

[Besoeker]

But load voltages are.

You mean the voltages change their phase relationships from one end of the wire to the other??
In the words of that choleric tennis player from a few years ago, "You cannot be.....etc..."

 

[T.M.Haja Sahib]

You mean the voltages change their phase relationships from one end of the wire to the other??

Have you read the post # 353 ?
What will you say then?

 

[Besoeker]

Have you read the post # 353 ?

Yes. It's nonsense.

 

[T.M.Haja Sahib]

It's nonsense.

No.You may use the same oscilloscope used for demontrating voltage waveshapes of 240V/120v supply here also.You can display both the voltage waveshapes 120V and -120V.Will you please do it?

 

[Besoeker]

No.You may use the same oscilloscope used for demontrating voltage waveshapes of 240V/120v supply here also.You can display both the voltage waveshapes 120V and -120V.Will you please do it?

You just don't get it.

From your post #380:

the two load voltages are in phase.Same is true for any other instantaneous values of Vmsin(wt) and Vmsin(wt+n)...

Let me repeat
V_msin(ωt) and V_msin(ωt+π) are not in phase.
If they were in phase, you could connect both ends of the 120-0-120 transformer together with no deleterious effect.
They're not and you can't. Don't even think about trying it.

 

[T.M.Haja Sahib]

You just don't get it.

You turned down my request to put in your scope the two voltages one from one end to the other and the second in the reverse direction of the 120v single phase supply to see for yourself that there will be 180 degree out of phase voltage wave shapes.Can't you concede to our request?

Let me repeat
V_msin(ωt) and V_msin(ωt+π) are not in phase.
If they were in phase, you could connect both ends of the 120-0-120 transformer together with no deleterious effect.
They're not and you can't. Don't even think about trying it.

Let me bring to your attention that voltages from V1 to N, and N to V2 are discussed here . They are in phase.

 

[jim dungar]

I didn't revert to RMS. It was never anything other than that.

But, as they say, your wish is my..........etc.

Where V_m =120*sqrt(2)
And Im = 120*sqrt(2)

That more to your liking?

I prefer these directions, as the math doesn't need to be tweaked when the neutral is not a common conductor:

 

[T.M.Haja Sahib]

I prefer these directions, as the math doesn't need to be tweaked when the neutral is not a common conductor:
View attachment 6416

Your preferred diagram also shows a common neutral.........

 

[pfalcon]

Nonsense! Some mistakenly call the two legs of a residential service phases. Any extra phases must be provided by a separate generator. You can't deny if you observe V1n and V2n on a scope, you see different phase angles from a single phase transformer.

I certainly can deny that claim. If I see them on a scope I'm looking at the SAME phase angle from two different views.

The subscripts 1n and 2n mean V1 with respect to N and V2 with respect to N, therefore they must be measured with respect to N. If you measure them any other way, you are measuring something different. It can't be any clearer.

Subscripting 1n means from 1 to N not "with respect to". And since voltage is a difference equation it's with respect to both V1 and N, not just N. So yes, it can be clearer.

Maybe in practice, but not in the ideal case. I am making the point that the common winding should not be a factor in this discussion.

Except that reverses the whole point of this thread. IDEALLY, residential single-phase is One phase with One phase angle with Neutral being a Voltage Divider. In PRACTICE this can be ignored and the system can be handled as though it was two separate voltage sources 180 degrees out of phase. Yet in PRACTICE if you tried to use separate sources you'd need far more complicated designs to keep the phases in-sync.

 

[pfalcon]

Interesting reading .......lots of it over my head. So what is the correct terminology for

two hots and one common or neutral ?

I would call L1 and L2 "legs". To call them "phases" implies a two-phase system which carries a separation of 90 degrees.

Agreed.

 

[pfalcon]

Correct.The instantaneous value changes from instant to instant.At one particular instant the voltage vector V1n is 120V and V2n is -120V.So what are the corresponding instantaneous currents in the hot conductors and neutral?Please answer it.

On single-phase residential ideally there is no instantaneous current on N at any time. Power is being transmitted between V1 and V2. N only carries current from unbalanced loads.

 

[pfalcon]

Well........
L1 is at +170V when L2 is at -170V wrt N at the same point in time. They cross zero at the same point in time but going in opposite directions.
I don't see how one can reasonably construe that as being in phase and, if not in phase, it must logically follow that they are out of phase and, if out of phase, it must logically follow that there is more than one phase.

For starters you can't reverse your time rates of change when determining whether they're in phase. Which is exactly what you're doing every time you choose neutral as your reference point for your scope. You're measuring one leg in a "forward" direction and the other leg in the "backward" direction.

 

[kwired]

Deleted due to repetition.

Hate to get too many posts in this thread, especially if one is a repeat:happyyes:

 

[roger]

Deleted due to repetition.

Hate to get too many posts in this thread, especially if one is a repeat:happyyes:

Yeah, I don't think Sahib is really trying, it's because he doesn't want to admitt Bob was right.

There are two ways to handle this.

For me I just accept 'because we do'

The other way takes 600 forum posts.


Good luck!

Roger

 

[K8MHZ]

Yeah, I don't think Sahib is really trying, it's because he doesn't want to admitt Bob was right.



Roger

When I first read Bob's post, I thought he was exaggerating (600 posts, yeah, right!).

Now with close to 400 and no signs of slowing down, this thread reminds me of the Centralia, PA coal fire.

Or the Energizer Bunny.

Just curious, is the moon single phase?

 

[rattus]

Well........
L1 is at +170V when L2 is at -170V wrt N at the same point in time. They cross zero at the same point in time but going in opposite directions.
I don't see how one can reasonably construe that as being in phase and, if not in phase, it must logically follow that they are out of phase and, if out of phase, it must logically follow that there is more than one phase.

Bes, IMHO any voltage obtained by inversion is not properly called a phase. A "phase" must be provided by a separate generator and the phases must drive two or three phase loads. So the open wye is single phase for example.

 

[ronaldrc]

Bes, IMHO any voltage obtained by inversion is not properly called a phase. A "phase" must be provided by a separate generator and the phases must drive two or three phase loads. So the open wye is single phase for example.

Rattus:Thats cute, you should have been a Lawyer.

But don't forget inversion means to change the polarity not shift it in time.

 

[jim dungar]

Your preferred diagram also shows a common neutral.........

Yeah it does, why is that an issue?
Two correct and valid ways to make the math work in order to analyse a single circuit, is that really a surprise?