Why is residential wiring known as single phase?

[Besoeker]

So is a conventional wye system, if you include line-to-line voltages.

It isn't a conventional wye system and no line to line voltages are used. The six phases are 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)

 

[rbalex]

It isn't a conventional wye system and no line to line voltages are used. The six phases are 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)

Yes - so? Then it's still a glorified three-phase system.

We already clarified that

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

are identities, right?

 

[Besoeker]

Yes - so? Then it's still a glorified three-phase system.

We already clarified that

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

are identities, right?

And thus:

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

So, still six phases chum.

 

[rattus]

And thus:

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

So, still six phases chum.

Yes, six phases since phase is equivalent to the argument of the sinusoid which describes the wave in question. Six arguments, six phases! It is a hexaphase circuit albeit from a triphase service.

 

[mivey]

There you go again claiming I said something some voltages were not real.

I made no such claim in my post. I told you what your post sounded like and asked for clarification. I was not trying to confuse you. It was a simple question that only required a simple answer sans the guff. I guess it was too much to ask for.

If you claim that we do generate negative voltages...

Do you deny that an AC signal reverses direction every 1/2 cycle? The positive and negative is an arbitrary assignment we make.

then the negative waveform of -Vnb and the positive waveform of Van start at the exact same time 't0' therefore Vbn and Van have the same phase constant, because -Vnb=Vbn=-Van.

Two waves with a 180? displacement do not have the same phase constant and I challenge you to find where math or physics books support that claim.

when you assign direction by including subscripts then you ignore what the subscripts mean.

I did not ignore the meaning but used them to convey meaning. Do you claim that subscripts do not indicate relative direction?

I said you need to acknowledge when you have performed the inversion.
Ohh, maybe you are using a different dictionary definition of 'inversion'

Inversion: a reversal of position, order, form, or relationship...

I did not start with Vnb then invert it to get Vbn. I started with Vbn so no inversion was required.

The voltage difference between two points has no direction it is simply V.

And you want to accuse me of obfuscation? Do you really see value in discussing the difference between voltage and potential difference?

What part of 'equality' do you not understand?
You ould have written (-sin([wt+])=sin([wt+x]+PI), or sin([wt+x]) = -sin([wt+x]+PI): WOW. Logic, common sense, experience, the opinions of experienced engineers, and the absence of any supported information to the contrary tells me the phase is (wt) when x=phi=0.

So do you now join rbalex in saying that two waves that have a phase difference have the same phase?

The minus sign in front of the function is not part of the amplitude but is part of the phase constant. The amplitude is the maximum distance from the center of oscillation. The direction can be different, but the distance is the length of the path, and we don't have negative lengths.

 

[mivey]

So, still six phases chum.

Well, if two waves that have a phase difference can have the same phase, I guess three can equal six.

 

[jim dungar]

I did not start with Vnb then invert it to get Vbn. I started with Vbn so no inversion was required.

Not that it matters, because eventually the discussion will come back to the fact that Vbn=-Vnb or -Vbn=Vnb.

To get your two waveforms separated by 180? from a single set of terminal B and N requires some type of 'opposite' Two points cannot really have a negative difference, therefore a result containing a negative sign, simply means that the result is opposite the actual difference. Voltage does not really have direction, but we arbitrarily assign one for analysis purposes, thus yielding the equality we have been using for thousands of posts:Vxy=-Vyx.

Lets enter the ideal world that Rattus wants us to be in, at Time t0 spin your 120/240V generator;
Does a voltage appear between terminals A and N at the same exact time that a voltage occurs between terminals B and N?
Do we have to wait 8.33-10msec (60 or 50hz) before two voltages can be sensed?

Now take the wye system, you keep wanting to bring up, at Time t0 spin your 208Y/120V generator;
Does a voltage appear between terminals A and N at the same exact time that a voltage occurs between terminals B and N?
Do we have to wait 2.78-3.33msec (60 or 50hz) before any two voltages can be sensed?

During either of the two examples above: Is the generator ever taking away a (i.e. the equivalent of 'producing negative') voltage between any two points? While mathematically accurate, that does not sound good, so how about; Is the generator ever producing a voltage opposite of what it is designed to produce?

 

[jim dungar]

If you evaluate the phasors in a delta, the sum will be zero.

Thank you for pointing out the obvious: the sum of the voltages in a three phase delta circuit =0.

I know you didn't say it but I'll bet the same things occurs if we sum all the voltages in a wye circuit, or even Besoeker's hexaphase circuits.

So, this is simply another confirmation of the math: Vbn=-Vnb

 

[Besoeker]

Yes, six phases since phase is equivalent to the argument of the sinusoid which describes the wave in question. Six arguments, six phases!

Quite.
It seems so simple and obvious. Yet it is being disputed.

 

[rbalex]

And thus:

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

So, still six phases chum.

Are you saying

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

aren't identities?

Or are you saying every time you can use a different argument for the same function a new "phase" magically appears?

 

[jim dungar]

It seems so simple and obvious.

The relationship Vbn=-Vnb, means equal, two things happening at the same time. This also seems so simple and obvious.

I noticed you never posted oscilloscope tracings from the circuit Mivey posted where he had voltage Van@0 and Van@0 in parallel and in series with Vbn@180 and Vnb@0 in parallel.
At that time I postulated the waveforms for his Vbn and Vnb would have the same 'phase'

 

[Besoeker]

Well, if two waves that have a phase difference can have the same phase, I guess three can equal six.

Droll. And you have a point. To enter this discussion room you need to abandon certain things at the door.

• Logic
• Mathematics
• Circuit design
• Physical implementation
• And, above all, decades of experience in the field.

 

[Besoeker]

The relationship Vbn=-Vnb, means equal,

It also means Vbn ≠ Vnb.
What's the relevance to the discussion?

 

[rattus]

Thank you for pointing out the obvious: the sum of the voltages in a three phase delta circuit =0.

I know you didn't say it but I'll bet the same things occurs if we sum all the voltages in a wye circuit, or even Besoeker's hexaphase circuits.

So, this is simply another confirmation of the math: Vbn=-Vnb

Trying to make a point Jim.

In the ideal wye, yes, but there is no point in summing the phasors in a wye since they are connected tail to tail. There is a point in summing (phasorially) between Va and Vb say. Starting with Vb to N, that phasor subtracts, then from N to Va, that phasor adds. The result is Vab = 208V @ some angle.

I don't see that Vbn = -Vnb is important even if it is true.

 

[rattus]

Droll. And you have a point. To enter this discussion room you need to abandon certain things at the door.

• Logic
• Mathematics
• Circuit design
• Physical implementation
• And, above all, decades of experience in the field.

How long you been at it Bes?

 

[rattus]

What part of 'equality' do you not understand?
You ould have written (-sin([wt+])=sin([wt+x]+PI), or sin([wt+x]) = -sin([wt+x]+PI): WOW. Logic, common sense, experience, the opinions of experienced engineers, and the absence of any supported information to the contrary tells me the phase is (wt) when x=phi=0.

Jim, 'x' should be REPLACED with a numerical value, in this case 0 and PI. There is no point in lugging around this unknown constant. It IS the phase constant.

Remember MINUS sin(wt) is a different function from PLUS sin(wt). That is where you and others have jumped the track to come to an illogical conclusion. Why do I say this? Because it is obvious that the waves are separated by PI radians. Ergo, they carry different phases.

This gives us two phases from a SINGLE PHASE SOURCE. Split phase you know!

I would venture to say that you never heard of it until a few days ago. If that is not the case, then where did you learn it?

I would think a university trained engineer would be more than willing to provide references.

 

[rattus]

Tricky Trig, or How You Have Been Bamboozled;

Tricky Trig, or How You Have Been Bamboozled;

Some on this forum have used a trig identity to show that that sin(wt + PI) is MINUS sin(wt). Well duh! I have always known that. Then the phase of PLUS sin(wt) (which is the other function) is extracted. Well duh again! Then ignoring the NEGATIVE sign, the claim is made that (wt) is the phase for MINUS sin(wt). Here is where the train is derailed.

Fact is that the phase of MINUS sin(wt) is (wt + PI).

We must compare sines to sines, NOT sines to MINUS sines (not signs). Maybe that would read better if I used cosines.

Those who believed this hogwash have been had!

 

[jim dungar]

Remember MINUS sin(wt) is a different function from PLUS sin(wt). That is where you and others have jumped the track to come to an illogical conclusion.

Wow, -Vm*sin(wt) NE Vm*sin(wt)
Could you provide the reference for this?

I am still trying to figure out why you think:

I don't see that Vbn = -Vnb is important even if it is true.

Other than that it proves a waveform and its inverse have the same phase, because they both occur at the same point in time..

From what I can tell:
Your vocabulary, and maybe even your dictionary, is different than mine.
You don't see why physical connections are important.
You don't see why trig identities are important.
You seem intolerant of choosing a reference other than neutral.
You may not understand, or accept, the fact that redirecting or inverting a phasor by 180? is an identical action to putting a negative, or minus sign, in front of the original value. with the result of creating a double negative when you then subtract the 'new' phasor.


Here is a reference for you, it even includes colored pictures. It discusses audio waves, but I think you might agree it is applicable to electricity also. Yes I know it includes phrases that you may not want to hear including 'in polarity' and 'out of polarity'
http://communitypro.com/files/literature/tech notes/POL_​PHASE_​TECH.pdf


communitypro.com/files/literature/tech notes/POL_​PHASE_​TECH.pdf

 

[rattus]

I am still trying to figure out why you think:

Other than that it proves a waveform and its inverse have the same phase, because they both occur at the same point in time..

Yes Jim, their zero crossings occur at the same time, but their peaks and troughs do NOT. That is they have different phase constants. In this case one is wt + 0; the other is wt + PI.

If the phase constants are the same, then they would overlie each other--assuming the same amplitudes. They don't.

If their phase constants are different, their phases are different. That ought to be self evident.

 

[jim dungar]

Yes Jim, their zero crossings occur at the same time, but their peaks and troughs do NOT.

That is because one is the inverse of the other. Not because one waveform is time displaced from another.

Select the 'invert' option on the scope. Does it displace the waveform in time, or simply provide its 'opposite polarity'?

Waveforms are not displaced in time simply by swapping reference points, B versus N. There is only a single voltage between terminal B and N, therefore there can only be a single voltage waveform.

I'm guessing you didn't look at the reference I posted concerning phases and polarities.