Just to record a phasor reference

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rattus

Senior Member
You state phase has official definition yet all along you have been arguing for absolute answers in all these threads.
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Yes, it does, but that does not prevent us from labeling the three lines in a wye for example as phase A, phase B, and phase C.

When we say phase A for example, we mean the voltage on line A with a unique phase angle which is different from the phase angles of phases B and C. It all goes back to the official definition of phase which is the argument of the sinusoid describing the waves.

I believe in some texts, 'static phase' is defined as opposed to 'instantaneous phase'. That would simply be the phase angle, and that is what we deal with most of the time.
 

steve066

Senior Member
The simple fact is that if

Nothing can be done with the phasor diagram to change this fact. It is true even without a phasor diagram.

They are inverses. Inverses are PI radians apart! Nuf sed!
So that is true because:


Yes, but the reference is stated to be the neutral, and the voltages are Van and Vbn. So I am completely right.
Which is true because:

I say because I stated that the reference was the neutral. It was my post after all.
 

steve66

Senior Member
And your point is?
I think its obvious. All of your statements hinge on your requirement that we all make the neutral the reference. Its only your own refusal to look at the problem any other way that supports your statements.

Even if we used the neutral as the reference, your statements are still incorrect. But that is a whole other argument.
 

steve66

Senior Member
Two hots and one neutral makes a case for the neutral being a common sense choice as a reference.
In my opinion, common sense would be to look at this as two windings, with the reference on the bottom of each winding.

Then they are simply two windings in series, with both voltages in phase. And Kirchoffs voltage law tells us that the resulting voltage across both windings also in phase.

Its that simple.
 

rattus

Senior Member
I think its obvious. All of your statements hinge on your requirement that we all make the neutral the reference. Its only your own refusal to look at the problem any other way that supports your statements.

Even if we used the neutral as the reference, your statements are still incorrect. But that is a whole other argument.
That is the whole point. We are discussing the voltages on L1 and L2, not the voltage on the neutral. The neutral is the obvious choice for a reference.

The phases of V1n and V2n must be separated by PI radians for Bes's full wave rectifier to work properly. That is why he correctly states that there are 2 phases albeit from a single phase transformer.

Now tell my why my statements are incorrect.
 

rattus

Senior Member
In my opinion, common sense would be to look at this as two windings, with the reference on the bottom of each winding.

Then they are simply two windings in series, with both voltages in phase. And Kirchoffs voltage law tells us that the resulting voltage across both windings also in phase.

Its that simple.
You can look at it that way, but that is not the only way, nor is it the best way. Even so, that does NOT change the voltage on L2 which is properly described as,

V2n = 120Vrms@PI

rather than

V2n = -120Vrms@0

which is awkward

V2n is still out of phase with V1n!
 
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steve66

Senior Member
Now tell my why my statements are incorrect.
Uh, I think I already did that. But here it is again in review:

You said:

The simple fact is that if

V1n = 120Vrms @ 0
then,
V2n = 120Vrms @ PI

Nothing can be done with the phasor diagram to change this fact. It is true even without a phasor diagram.

They are inverses. Inverses are PI radians apart! Nuf sed!
And I said that's not true, if we pick different reference points we have different phase angles, and thats where you started insisting we use your reference points because that is the only way your arguement makes any sense at all.

And then I posted that if we use the bottom of each winding as the reference then all the voltages are in phase, and you agreed, which again proves you were incorrect.
 

rattus

Senior Member
Uh, I think I already did that. But here it is again in review:

You said:



And I said that's not true, if we pick different reference points we have different phase angles, and thats where you started insisting we use your reference points because that is the only way your arguement makes any sense at all.

And then I posted that if we use the bottom of each winding as the reference then all the voltages are in phase, and you agreed, which again proves you were incorrect.
But, V1n and V2n are DEFINED relative to the neutral. Those are the conditions for my argument. Those are the voltages we are discussing. You must accept those conditions before you start nit picking. After all, it is MY post!
 

rattus

Senior Member
More:

More:

I repeat:

If we DEFINE V1n and V2n as,

V1n = 120Vrms@0
V2n = 120Vrms @PI

These voltages will ALWAYS be referenced to 'n'. They will always be PI radians apart. Nothing can be done about it. That is the way transformers work!

If you define to a different reference, that does NOT change V1n and V2n. You are defining a new set of voltages!
 

pfalcon

Senior Member
Location
Indiana
As far as I know, there is no official definition for the term 'phase' as used to describe the lines of a multiphase system. But, it is clear that it means that the voltages on legs A, B, and C carry different phase angles, namely A, B, and C. So there is no difference.
Why is this being dragged off to three-phase again? How about we stick with the phasors?

You had better come up with a better explanation for Rcos and Lcos. Perhaps you could explain a bit further and tell us how I*L*cos is used? I*X[SUB]L[/SUB] makes sense but I*L is just plain wrong. And, the use of trig terms in this expression is wrong as well, plus we are not talking about any currents or inductances anyway.
argumentium ad hominem, an attack on my credibility rather than my statements which iwire has already cautioned us about. But you should know, my math training comes from a Dr of Physics, a Dr of Mathematics, and three Masters in Mathematics. How about we get back to phasors rather than personal attacks?

I have a split phase system in my home, and I am quite sure the phases on L1 and L2 are separated by PI radians. I am sure Tektronix would tell me the same, but try as I may, I cannot change that phase relationship without climbing the pole and rewiring the transformer. Not sure I could anyway since there are only three bushings.
And once again, you're using the overloaded word phase according to definition (2). Which once again by definition (2) L1 and L2 are opposed phases hence argumentium ad nauseaum. Repeating def (2) over and over will never make it apply to "Why we call it single phase?". Definition (1) is required. I believe you are stuck in the proverbial rut. Prove that measuring L1 and L2 relative to neutral can be used to determine how many system (not voltage) phases are present.

Yes, it does, but that does not prevent us from labeling the three lines in a wye for example as phase A, phase B, and phase C.

When we say phase A for example, we mean the voltage on line A with a unique phase angle which is different from the phase angles of phases B and C. It all goes back to the official definition of phase which is the argument of the sinusoid describing the waves.

I believe in some texts, 'static phase' is defined as opposed to 'instantaneous phase'. That would simply be the phase angle, and that is what we deal with most of the time.
Round and round back to three-phase again. When YOU say "phase A" you are using definition (2) which provides no more proof to why three-phase is called three-phase than what you've provided for single-phase. Adding three-phase just adds obfuscation to this thread.

That is the whole point. We are discussing the voltages on L1 and L2, not the voltage on the neutral. The neutral is the obvious choice for a reference.

The phases of V1n and V2n must be separated by PI radians for Bes's full wave rectifier to work properly. That is why he correctly states that there are 2 phases albeit from a single phase transformer.

Now tell my why my statements are incorrect.
We are supposed to be discussing "Why we call it single-phase?". L1, L2, N are all valid reference points. And again, I will tell you why your statements are ... wait for it ... repititious though it is ... CORRECT BY DEFINITION (2) but don't answer "Why we call it single-phase?" once again.
 
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rattus

Senior Member
This thread is entitled, "Just to record a phasor reference", the other thread is closed.

Now I must respectfully ask you, what is meant by I*[Rcos + Lsin]? What is the argument of the trig functions? Is it wt? Phi? (wt + phi)?

Were you trying to write,

V = I[R + jwL] where V and I are phasors?

I don't understand this at all, please explain.

BTW, nothing personal about it, just searching for the TRVTH.
 

pfalcon

Senior Member
Location
Indiana
This thread is entitled, "Just to record a phasor reference", the other thread is closed.
:)
I don't understand this at all, please explain.
BTW, nothing personal about it, just searching for the TRVTH.
the TRVTH is out there :)

... This is supported by the basic circuit concepts:
The resistance/inductance of AN == BN since this is how we build a secondary coil (sorry about the obviousness).
The secondary is not actually a supply but an induced coil or load where each leg is V = I [ R + jwL ].
[ R + jwL ] does not have direction. The direction of I is imposed by the primary coil and is therefore traveling from A to B or from B to A at any given instant.
 

rattus

Senior Member
:)
This is supported by the basic circuit concepts:
The resistance/inductance of AN == BN since this is how we build a secondary coil (sorry about the obviousness).
The secondary is not actually a supply but an induced coil or load where each leg is V = I [ R + jwL ].
[ R + jwL ] does not have direction. The direction of I is imposed by the primary coil and is therefore traveling from A to B or from B to A at any given instant.
the TRVTH is out there :)
The secondary may be modeled as two ideal sources for purposes of this discussion. It is done all the time.

First of all, what happened to I[Rcos? + Lsin?]? And what about the arguments? You conveniently replaced that expression with I[ R + jwL] which you lifted from my response.

And how did the current, I, find its way into this thread?

Yes indeed, the impedance, R + jwL, carries a phase angle, as well as V and I which are also phasors.
 

pfalcon

Senior Member
Location
Indiana
The secondary may be modeled as two ideal sources for purposes of this discussion. It is done all the time.
Because separate sources have separate motive fields and are therefore not single-phase. Therefore that model is outside the scope of establishing correct phasors for a 120/240 system.

First of all, what happened to I[Rcos? + Lsin?]? And what about the arguments? You conveniently replaced that expression with I[ R + jwL] which you lifted from my response.
Not needed. Confused you. Your expression carries the important current element so I can go with that. Holding on the prior expression would drag the discussion off-topic.

And how did the current, I, find its way into this thread?
The current is required to determine the correct phasor direction.

Yes indeed, the impedance, R + jwL, carries a phase angle, as well as V and I which are also phasors.
(R+jwL) does not carry a phase angle. It's the phase deflection imposed on I passing through the secondary coil based on the direction of the current. The phasor direction for the voltage starts with the phase angle of I and is deflected to lead or lag because of (R+jwL).

The primary EMF (supply) drives the current in a unified direction (call it <0) across the secondary coil (load) from A through N to B.
V=I(2*[R+jwL])=I[sub]an[/sub][R+jwL]+I[sub]nb[/sub][R+jwL]=V[sub]an[/sub]+V[sub]nb[/sub]
Because the secondary is a load to the primary and there is only one EMF driving the current: I[sub]an[/sub]==I[sub]nb[/sub]
Because of how we construct secondary coils: [R+jwL][sub]an[/sub]==[R+jwL][sub]nb[/sub]

So now you move your reference point to N.
V[sub]nb[/sub] == -V[sub]bn[/sub] ~= V[sub]an[/sub] < 180
which is where you stop. And which is correct in field practice if all you're doing is working on voltage.

But if you wish to comment about the system phase then you have to continue:
I[sub]nb[/sub] == -I[sub]bn[/sub] ~= I[sub]an[/sub] <180

and your power resolves as:
V[sub]an[/sub]*I[sub]an[/sub]+V[sub]bn[/sub]*I[sub]bn[/sub] == V[sub]an[/sub]*I[sub]an[/sub]+V[sub]bn[/sub](<180)*I[sub]bn[/sub](<180) == 2*V[sub]an[/sub]*I[sub]an[/sub]
which means the power to the system is all single-phase.
 

rattus

Senior Member
I refuse!

I refuse!

Because separate sources have separate motive fields and are therefore not single-phase. Therefore that model is outside the scope of establishing correct phasors for a 120/240 system.


Not needed. Confused you. Your expression carries the important current element so I can go with that. Holding on the prior expression would drag the discussion off-topic.


The current is required to determine the correct phasor direction.


(R+jwL) does not carry a phase angle. It's the phase deflection imposed on I passing through the secondary coil based on the direction of the current. The phasor direction for the voltage starts with the phase angle of I and is deflected to lead or lag because of (R+jwL).

The primary EMF (supply) drives the current in a unified direction (call it <0) across the secondary coil (load) from A through N to B.
V=I(2*[R+jwL])=I[sub]an[/sub][R+jwL]+I[sub]nb[/sub][R+jwL]=V[sub]an[/sub]+V[sub]nb[/sub]
Because the secondary is a load to the primary and there is only one EMF driving the current: I[sub]an[/sub]==I[sub]nb[/sub]
Because of how we construct secondary coils: [R+jwL][sub]an[/sub]==[R+jwL][sub]nb[/sub]

So now you move your reference point to N.
V[sub]nb[/sub] == -V[sub]bn[/sub] ~= V[sub]an[/sub] < 180
which is where you stop. And which is correct in field practice if all you're doing is working on voltage.

But if you wish to comment about the system phase then you have to continue:
I[sub]nb[/sub] == -I[sub]bn[/sub] ~= I[sub]an[/sub] <180

and your power resolves as:
V[sub]an[/sub]*I[sub]an[/sub]+V[sub]bn[/sub]*I[sub]bn[/sub] == V[sub]an[/sub]*I[sub]an[/sub]+V[sub]bn[/sub](<180)*I[sub]bn[/sub](<180) == 2*V[sub]an[/sub]*I[sub]an[/sub]
which means the power to the system is all single-phase.
There are so many errors in this post that I will not even try to respond.
 
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