Why is residential wiring known as single phase?

[K8MHZ]

Are you familiar with the dot notation. Would help if I added that?

Maybe....

A graphic representation would be better for me....

But, if you start with the systems I know, single phase center tapped, and 3 phase wye, I should be able to figure out the actual direction of the windings on other systems, right? Then when I see it on the hexaphase system, hopefully it will make some sense to me.

Thanks.

Also, I did some snooping around about hexaphase systems and found one schematic using one three phase wye and one three phase delta on the secondary to get six secondary phases. I thought that was intriguing.

 

[ronaldrc]

I see it as post 1 = post 2



Roger

This group would never over complicate anything.

It took them 650 post to finally get it through my thick skull, That
I am not smart enough to undersatand what they are talking about. :roll:

I am just an under educatied Electrician.

 

[rattus]

Just a follow-up. There is no argument that mathematically an inversion can appear as a phase shift. That's why it is perfectly fine to say they are "equivalent", and you'll get no argument from me.

Where you're going to get an argument from me is when you say it is a phase shift instead of just being equivalent to one. If it truly was a phase shift and not just a mathematical equivalency, then the setup I described above would show the noise on both positive peaks.

Everyone knows that an ideal xfrmr does not add any delay. Maybe we should say that the fundamentals of V1 and V2 are out of phase by 180 degrees, but why complicate things? This trivial point does not answer the original question.

 

[K8MHZ]

Everyone knows that an ideal xfrmr does not add any delay. Maybe we should say that the fundamentals of V1 and V2 are out of phase by 180 degrees, but why complicate things? This trivial point does not answer the original question.

Isn't there a 30 degree shift between the primary and secondary of a Wye-Delta transformer?

I swear I heard that somewhere....

 

[rattus]

Yes but,

Yes but,

Isn't there a 30 degree shift between the primary and secondary of a Wye-Delta transformer?

I swear I heard that somewhere....

That is right, but the 30 degrees is not due to a time delay. With a wye/delta, we have three single phase xfrmrs. There is no delay in any one of them.

 

[rbalex]

Isn't there a 30 degree shift between the primary and secondary of a Wye-Delta transformer?

I swear I heard that somewhere....

Yes, there is; in fact, depending on the connections there can be any of six phase shifts (without playing other games with the windings) - it's irrelevant to the discussion.

And besides the ground up side of your avatar should be on the right

 

[K8MHZ]

That is right, but the 30 degrees is not due to a time delay. With a wye/delta, we have three single phase xfrmrs. There is no delay in any one of them.

Maybe I was thinking about time difference, which would not necessarily mean the difference was due to a delay, correct?

 

[gar]

120211-1343 EST

Relative to the original post I will describe the normal US residential arrangement as a "single phase system" as a way of giving it a name, and I can accept calling it "single phase" for a shorter name. The argument for using this name is that at the input side of the distribution transformer there are only two terminals thru which power is supplied and thus at this point it is single phase.

I choose to describe the output from the center tapped secondary as two phases and I usually would call them phase A and phase B. Others disagree with this concept. But I suspect that many electricians will describe the two hot lines as different phases so that they have a convenient name to apply to the wires.

The DOT notation on a schematic is very important as a unique means of identification of transformer phasing. K8MHZ I have never seen an electrical engineering drawing where transformer phasing was defined by the direction of the swirls of the schematic drawing of a transformer.

Whether a center tapped secondary is fabricated as one single coil with a center tap wire soldered to the mid-point of the coil, or is made from two identical coils makes no difference.

Thus, consider the two coil secondary approach.
Label one coil X1 - X2 with the dot adjacent to X2, and
label coil two X3 - X4 with its dot adjacent to X4.

Note, when talking about phase it is only relevant to a sine wave. The assumption is that the sine wave is continuous from -infinity to +infinity in time. Practically it does not have to exist for that long of a time.

Connect X1 to X3, but do not connect X2 to X4.
What is the voltage difference between X2 and X4?
Very near zero because the two voltages are in phase. Virtually no phase difference.

Connect X2 to X3, but do not connect X1 to X4.
What is the voltage difference between X1 and X4?
Very near 2 times either X1 - X2 or X3 - X4 because the two voltages are 180 degrees out of phase. Big sparks fly if X1 is connected to X4. This is one reason an electrician must understand the phase relationship.

Next get a phase sensitive voltmeter like what I use with an LVDT. Get your phase reference from the primary of the transformer. Now measure the voltage from X2 to X1 and assume it is +120 V. Do the same from X4 to X3 and the result will also be +120 V. Measure from X3 to X4 and the result is -120 V.

Use an ordinary non-phase sensitive voltmeter and the above readings are all just 120 V.

You can put any names you want on the above voltages and use some other name for phase, but the measured results will be the same.

To confuse things more in a three phase system with a delta primary, only 3 phases at the input, without center tapped secondary windings from each phase, and a Y secondary I really have 6 phases available. These are V_AN, V_BN, V_CN, V_AB, V_BC, V_CA. Is this real useful, probably not, but they are 60 deg apart, and none are the same phase.

.

 

[K8MHZ]

Yes, there is; in fact, depending on the connections there can be any of six phase shifts (without playing other games with the windings) - it's irrelevant to the discussion.

And besides the ground up side of your avatar should be on the right

If you take note, the vast majority of the posts in this thread are irrelevant to the OP's first post.

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

So, to actually be relevant, we should only be addressing two things. One, the fact that 'every sparky' does not subscribe to the two phase debacle, and two, there are not two phases in a standard single phase residential panel.

All else is superfluous.

The crux of the biscuit is that single phase residential panels are called single phase because of the existence of only one phase, hence the use of the term 'single' to indicate the phase used in the panel and some, if not several or perhaps up to as high as many, of us sparkies know we are working with only one phase.

And furthermore, the picture in my avatar is of a cover / receptacle combination that does not belong to me. It was on the wall of a recycling facility that I visit from time to time. There is no physical way to put the ground up side on the right. That is something you will have to take up with the manufacturer, whom I am sure has long since gone out of business due to excess expenditures on engineers that liked to drag out simple issues by injecting every conceivable notion of conjecture into a discussion supported by page after page of math followed by an even longer counter to the conjectures by other engineers supported by page after page of different math.

:lol:

 

[rattus]

Maybe I was thinking about time difference, which would not necessarily mean the difference was due to a delay, correct?

The 30 degree shift stems from the phase angles of the L-L voltages as opposed to the angles of the L-N voltages on the wye side. It is clear when you view the wye phasor diagram.

 

[gar]

120211-1600 EST

K8MHZ:

When you consider a sine wave continuous in time, then phase shift and time delay become equivalent measurements with an appropriate scaling factor.

See http://en.wikipedia.org/wiki/Phase_(waves) which I have previously referenced.

.

 

[K8MHZ]

The 30 degree shift stems from the phase angles of the L-L voltages as opposed to the angles of the L-N voltages on the wye side. It is clear when you view the wye phasor diagram.

I'm sure it is.

 

[K8MHZ]

120211-1600 EST

K8MHZ:

When you consider a sine wave continuous in time, then phase shift and time delay become equivalent measurements with an appropriate scaling factor.

See http://en.wikipedia.org/wiki/Phase_(waves) which I have previously referenced.

.

OK, so was I right or was I wrong????

:?

 

[zbang]

And furthermore, the picture in my avatar is of a cover / receptacle combination that does not belong to me. It was on the wall of a recycling facility that I visit from time to time. There is no physical way to put the ground up side on the right. That is something you will have to take up with the manufacturer, whom I am sure has long since gone out of business...

FWIW, those four-direction covers are often used for event/temporary wiring. I've seen new-looking ones recently, but can't for the life of me remember who makes them.

 

[zbang]

Are you familiar with the dot notation. Would help if I added that?

I was wondering if the dots would show up, they tend to clear up a lot. Very common in audio diagrams.

 

[Besoeker]

Maybe....

A graphic representation would be better for me....

But, if you start with the systems I know, single phase center tapped, and 3 phase wye, I should be able to figure out the actual direction of the windings on other systems, right? Then when I see it on the hexaphase system, hopefully it will make some sense to me.

Thanks.[/quote]
I know that the 120-0-120 residential systems are generally two windings connected in series producing the equivalent of a centre tapped winding.
The hexaphase has a star connected arrangement of centre-tapped secondaries.
To that extent my diagram is a graphic representation. It shows six windings drawn at at 60deg intervals. The phase relationships of each is shown.

But, for consistency, maybe this will help.

Also, I did some snooping around about hexaphase systems and found one schematic using one three phase wye and one three phase delta on the secondary to get six secondary phases. I thought that was intriguing.[/QUOTE]

 

[Besoeker]

Thanks.

I know that the 120-0-120 residential systems are generally two windings connected in series producing the equivalent of a centre tapped winding.
The hexaphase has a star connected arrangement of centre-tapped secondaries.
To that extent my diagram is a graphic representation. It shows six windings drawn at at 60deg intervals. The phase relationships of each is shown.

But, for consistency, maybe this will help.

Also, I did some snooping around about hexaphase systems and found one schematic using one three phase wye and one three phase delta on the secondary to get six secondary phases. I thought that was intriguing.

It's a system commonly used on higher power systems and is called 12-pulse.
It employed to get lower harmonics in the supply.

 

[Besoeker]

I was wondering if the dots would show up, they tend to clear up a lot. Very common in audio diagrams.

I wondered that too but I was willing to give it a go.

 

[Rick Christopherson]

Everyone knows that an ideal xfrmr does not add any delay. Maybe we should say that the fundamentals of V1 and V2 are out of phase by 180 degrees, but why complicate things? This trivial point does not answer the original question.

If it is such a trivial point, then you would have no problem retracting the statement that resulted in this discussion. We both know it is not a trivial point and you are just playing games and trying to deflect away from the question posed to you.

Quit playing games.

Either defend your original statement or retract it.

 

[John120/240]

Ok, lets see it takes two hot legs to make single phase ? One hot & neutral is only one leg of

single phase ? Three hot legs is three phase ? Please make corrections where needed.