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- Mission Viejo, CA
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- Professional Electrical Engineer
Yes so it's still a glorified three-phase system unless you also include line-to-line voltages. THEN you can legitimately call it hexiphase.
Why is residential wiring known as single phase?
- Thread starter TimWA
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The service is three phase. The circuit is hexaphase. That's all.
T
T.M.Haja Sahib
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You mean V1n and Vn2 do not exist?
mivey
Senior Member
Do you think I have said it is not a valid reference? I have continually said that both references are valid.
If there is no neutral connection, then we have a different set of circumstances. Additional voltages are available when we add a neutral connection.
That is correct. But it is just not that the inversion does not create a time delay; neither do any of the other transformer configurations that create a phase shift because they are all the result of physical manipulations of the voltages.
Vbn has not been modified; it is the same as when it was created. The phase constant for Vbn includes PI, the phase constant for Vnb does not.
It will certainly produce different results. But before we digress, we are talking about voltages from different sets of terminals anyway: Van and Vbn are certainly different waves and they can have different fluxes.
That is what keeps baffling me about your position. The way you wrote your post reads as if you think only one voltage is "the real voltage". In this case it reads like you have said that only the "positive increasing" voltage is real. Vab is no more real than Vba but your wording makes it look like you think one is more real than the other. I know you also say both are real, so what do you mean by "We don't really generate a negative voltage"?
Also, "positive increasing" is a relative term. There is nothing that says both windings must be taken as "positive increasing" in the same direction. You can take both to be positive in the same linear direction or both positive relative to their common point and either way is valid. Both are really generated voltages.
They are not clones in every manner because they can have different fluxes.
The positive direction is not dictated by polarity marks so we also have two phasors pointed in opposite directions created at the same time.
Why do you think in order to get V4n that we have to rotate Vn4? The truth of the matter is that V4n is created at the same time that Vn4 is created. Both exist.
The fact that you sum V1n plus Vn4 does not mean that V4n is not there. The V4n voltage exists also.
If the truth be known, you are basing your premise on a voltage that was rotated from its real physical relationship to the primary anyway because the transformer has a 180? phase shift. Do you not see the peculiarity in trying to represent the physical inversion that negates the 180? phase shift as the "really generated" voltage?
First, the voltages Van and Vbn and Vnb and Vna all exist. We do not "rotate" one of them to "create" the other as they are all created at the same time. The voltages are there. We do not "rotate" the voltages because they were there before we connect to them and they will be there after we connect to them.
Second, we can take a potential difference. That does not mean we have to invert one of the voltages and then add them together. It is not (A) + (-B) but rather (A) - (B). We do not have to "invert" B to take the potential difference between points A & B.
mivey
Senior Member
I do not believe that to always be the case. Sometimes it makes life easier, but sometimes it makes life harder.
I mean the voltages in question are V1n and V2n.
Perhaps, but for the split phase and wye systems, it makes sense to me.
- Location
- Mission Viejo, CA
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- Professional Electrical Engineer
So is a conventional wye system, if you include line-to-line voltages.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
There you go again claiming I said something some voltages were not real. Instead of dealing with the facts, it seems you obfuscate by claiming I addressed issues I have purposely skipped over.
If you claim that we do generate negative voltages, 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.
gar
Senior Member
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- EE
120310-0927 EST
rbalex:
In your post 1084 there are three definitions given for phase.
None of these definitions of phase defined "same phase", and none required the function to be a sine wave. IEEE defines phase as the fractional part of a period. Nor does the definition explicitly define a phase difference between the function and an angular or time displacement of itself, or another function of the same period.
Period is not explicitly defined. A definition can be found here http://en.wikipedia.org/wiki/Periodic_function
It seems we need a definition of "same phase", and "phase difference".
Which of the following are of the same phase, and what are their phase differences relative to the first function? And why?
1. f1 = sin (wt + 0)
2. f2 = sin (wt + Pi/6)
3. f3 = sin (wt + Pi/4)
4. f4 = sin (wt + 15*Pi/16)
5. f5 = sin (wt + Pi)
6. f6 = sin (wt + 17*Pi/16)
7. f7 = sin (wt + 4*Pi/3)
8. f8 = sin (wt + 2*Pi)
.
rbalex:
In your post 1084 there are three definitions given for phase.
None of these definitions of phase defined "same phase", and none required the function to be a sine wave. IEEE defines phase as the fractional part of a period. Nor does the definition explicitly define a phase difference between the function and an angular or time displacement of itself, or another function of the same period.
Period is not explicitly defined. A definition can be found here http://en.wikipedia.org/wiki/Periodic_function
It seems we need a definition of "same phase", and "phase difference".
Which of the following are of the same phase, and what are their phase differences relative to the first function? And why?
1. f1 = sin (wt + 0)
2. f2 = sin (wt + Pi/6)
3. f3 = sin (wt + Pi/4)
4. f4 = sin (wt + 15*Pi/16)
5. f5 = sin (wt + Pi)
6. f6 = sin (wt + 17*Pi/16)
7. f7 = sin (wt + 4*Pi/3)
8. f8 = sin (wt + 2*Pi)
.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Wow do you obfuscate; when you assign direction by including subscripts then you ignore what the subscripts mean.
I never told you to invert anything. I said you need to acknowledge when you have performed the inversion.
Ohh, maybe you are using a different dictionary definition of 'inversion'
The voltage difference between two points has no direction it is simply V. If subscripts are used to simply keep track of different potentials then Van=Vna=Vbn=Vnb, for a two 120 windings in a center-tapped transformer. So simply combining any two of them via subtraction will result in 0V.
The equality of Vbn=-Vnb combing two opposite actions (a double negative).
If the subscripts mean nothing than the equality becomes Vx=-Vy.
I don't think so Jim. -Vnb = Vbn which is delayed by PI.
Let Van = 120Vrms*sin(wt + 0)
Let Vbn = 120Vrms*sin(wt + PI)
Their start points are PI radians apart.
Their phase constants are 0 and PI if we believe 'phase' = (wt + phi)
'phi' has been REPLACED by 0 and PI in the above examples.
I see no reason to introduce negative signs in the first place; just confuses the issue and leads to false conclusions.
- Location
- Mission Viejo, CA
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- Professional Electrical Engineer
Com'on gar,
Will I ultimately need to provide what the definition of what "is" is too? You have never accepted any of the formal definitions in the first place - so I have no obligation to provide or accept supplementary definitions. You offered a "personal" definition which I said was fine, but I had no obligation to accept it - which I didn't.
I finally started saying the "phases" of the voltage functions in a conventional 120/240V system are identical - which they are, by any of the three formal definitions.
What is the phase of (-sin(wt))
Well the 'phase' of PLUS sin(wt) is simply (wt),
but MINUS sin(wt) is a different animal, so let us apply a trig identity to remove the minus sign.
(-sin(wt))= sin(wt + PI)
Logic, common sense, experience, the opinions of four experienced engineers, and the absence of any supported information to the contrary tells me the phase is (wt + PI)! Go figure!
Well the 'phase' of PLUS sin(wt) is simply (wt),
but MINUS sin(wt) is a different animal, so let us apply a trig identity to remove the minus sign.
(-sin(wt))= sin(wt + PI)
Logic, common sense, experience, the opinions of four experienced engineers, and the absence of any supported information to the contrary tells me the phase is (wt + PI)! Go figure!
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- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
You are the one inserting negative signs. My formula of Van+Vnb=Vab does not contain a negative sign at all.
Do Vbn and -Vnb start at the same point in time?
Yes, they do, but Van and Vbn do NOT, and that is the issue.
Now, do you think Van and Vbn carry the same phase constant even if they start at different times?
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- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
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.
Phasors:
Phasors:
Phasors are complex numbers, and the preferred way to label a phasor is with a magnitude (always positive) and a phase angle. Tacking a negative sign in front of a phasor is poor form; this should be done only when subtracting phasors.
In evaluating a string of phasors, one traverses the phasors one at a time. From tail to head, one adds (phasorially); from head to tail, one subtracts.
If you evaluate the phasors in a delta, the sum will be zero.
If one evaluates the two phasors in an open wye, one phasor is added, the other subtracted to obtain the line to line voltage.
Phasors:
Phasors are complex numbers, and the preferred way to label a phasor is with a magnitude (always positive) and a phase angle. Tacking a negative sign in front of a phasor is poor form; this should be done only when subtracting phasors.
In evaluating a string of phasors, one traverses the phasors one at a time. From tail to head, one adds (phasorially); from head to tail, one subtracts.
If you evaluate the phasors in a delta, the sum will be zero.
If one evaluates the two phasors in an open wye, one phasor is added, the other subtracted to obtain the line to line voltage.
Jim, just take the expressions as they are. Logic tells me the expressions are OK as they are. Don't fall for this inversion nonsense. There is no need nor justification for it. All we need do is look at the arguments for the sines, one is,
(wt + 0)
the other is,
(wt + PI)
Two arguments, two phases.
Maybe you can provide a reference which supports your position, no one else can.
That was in response to my:
I assert again that there IS one firing pulse every 60deg for this arrangement.
You'd think I might know that considering I designed the firing circuit to do just that.
So I'm sorry, but you were just plain wrong to dispute that.
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