Battle of the Phases

[mivey]

By the way, who says engineers (real or fake) know everything anyway?

Reminds me of a story:

We designed a substation and we were arguing with the contractor about its construction. We showed him on our design plans that it would work and he was disagreeing. He finally had enough of us and said (paraphrasing): "You can build a craphouse on paper but it don't mean you can crap in it".

As it turns out, he was right and we were the engineers with 60+ years of experience. You can always find yourself in error.

 

[rattus]

102 and counting:

102 and counting:

Yeah, let's forget the key facts when they don't fit. Let's forget that both sources are actually coming from the same physical device. Because if we do this, then we can arbitrarily change the phase of one source relative to the other. Afterall, it is common practice by real engineers to arbitrarily change phase instead of using a minus sign.

Rick,

Why does it matter that these voltages derive from a common transformer?? Would it matter if these voltages derive from separate transformers? Separate generators?? Just treat the panel as a black box where we don't know the nature of the sources. Then you can't make that argument. You and others keep coming back to this argument which makes no sense. Give us a logical argument to support this idea. I have never heard one.

V1n and V2n, as defined, are 180 degrees out of phase. It is as plain as two traces on an oscilloscope. What you see is what you get.

 

[Rick Christopherson]

You can always find yourself in error.

This forum contains enough high-powered knowledge in its participants, that I am quite humbled by it. I know that one misstep in what I state will result in getting my hat handed to me. What I resent is when one member makes it a habit of belittling others under the guise of being an engineer, when that appears to not be true. Under any other discussion, I would never storm in here and pretend I know everything because I am an ?Engineer?. To the contrary, I am fully aware that there are a lot of people here that know far, far more than I do.

 

[Rick Christopherson]

Why does it matter that these voltages derive from a common transformer??

Actually, it does matter. However, this is an argument that I couldn't care less about. I have personally stated in public print, in one of the most commonly referenced electrical articles on the internet, that the two sources are out of phase. I stated it as a matter of convenience for the audience so they could better understand the concept. However, in a circuit analysis situation, it is not what I would ever state, and I would not change the phase of one half of a center-tapped transformer.

By the way, the only reason why I am in this discussion is because you said there was no neutral in the center-tapped delta system that I drew answering a different question before this thread was separated from the original. You never did respond to this.

 

[rattus]

Which is it?

Which is it?

Actually, it does matter. However, this is an argument that I couldn't care less about. I have personally stated in public print, in one of the most commonly referenced electrical articles on the internet, that the two sources are out of phase. I stated it as a matter of convenience for the audience so they could better understand the concept. However, in a circuit analysis situation, it is not what I would ever state, and I would not change the phase of one half of a center-tapped transformer.

By the way, the only reason why I am in this discussion is because you said there was no neutral in the center-tapped delta system that I drew answering a different question before this thread was separated from the original. You never did respond to this.

Just the facts, Rick. Just the facts. Don't give us the run around. If you can't come up with some logical answer just say so.

As for the neutral, I did respond with a definition. Furthermore you should read mivey's post #54.

I repeat for the nth time, "There is a neutral in the 120/240 subsystem, but not for the delta as a whole."

 

[crossman]

Rattus, another point could be made with the delta. If we did not ground anything, and there were no connections between the conductors I am proposing other than those in the windings themselves, , it would be entirely feasible to centertap the midpoint of ALL THREE xfmrs of the delta arrangement. Each of these "neutrals" could be used to feed loads between any other conductor of the system. There would actually be three single phase systems with their own neutral. (again. I am saying no ground connections which would cause short circuits)

And, as I look in the codebook, the definition of neutral point includes "midpoint of a single-phase portion of a three-phase delta."

Anyway, on this point, maybe it is semantics. But, the neutral is defined by the single-phase portion of the delta system, not the delta system as a whole.

I understand what you are saying.

 

[coulter]

... Third, I am glad you mentioned "vectors", although that term is obsolete. The preference today is "phasors". ...

I would not agree with that. You consider the term "vector" obsolete. You have a preference for blanket use of the term "phasor". And likely can find some references to agree with you. For the model limits you picked, what you propose will work fine. However, I find this methodology limiting.

That is not my preference. My preference is vector = non-rotating phasor, phasor = rotating vector.:roll: (You [pural] are susposed to see some wry humor here)
Why is that? Beause other models, with different limiting conditions, extend to multi-phase, rotating fields, sequence analysis, ... - which is what I work with. I don't do houses (except mine - DIY forever!)

Polar notation: Yes, using "magnitude/phase angle", my convention is to consider the magnitued to be unsigned. I won't insist anyone else follow my convention - but it does make it easier (for me) to do the math.

Paper fight: Enough already with the credentials wars. As far as I can tell, my stack of paper can beat up your (pural) stacks.:roll: Well except charlie's, he has a pretty high stack. And, I never noticed that I was one bit better at engineering the day before I got the paper than I was the day after.

carl

 

[Rick Christopherson]

Just the facts, Rick. Just the facts. Don't give us the run around. If you can't come up with some logical answer just say so.

As for the neutral, I did respond with a definition. Furthermore you should read mivey's post #54.

I repeat for the nth time, "There is a neutral in the 120/240 subsystem, but not for the delta as a whole."

I'm sorry. What part of "I don't care about this discussion" wasn't clear to you. There are no facts to give because I don't care what you want to call the system. Unlike other discussions, this one truly is a matter of semantics. Call it what you like as long as you don't change the definition. I don't care.

As for the Neutral, you are backpedaling to cover your mistake. You were more concerned about ridiculing me than you were about getting the facts straight. The diagram I drew clearly represents a system that contains a neutral in its proper form. You criticized the diagram, not the words, and for that, you are wrong, and you know that you are wrong. If I had stated this in text-only, you could have gotten away with saying I mis-spoke my intent. However, because this was graphical, you cannot claim I made a mistake in my words. The only mistake in this issue was when you incorrectly tried to correct me.

 

[crossman]

As far as I can tell, my stack of paper can beat up your (pural) stacks.:roll: Well except charlie's, he has a pretty high stack.

You guys are making me feel bad. I ain't nuthin' but a scummy construction worker.

 

[bcorbin]

You guys are making me feel bad. I ain't nuthin' but a scummy construction worker.

You've got nothing to feel bad about Crossman...there are some pretty "scummy" Engineers out there. And there are also a bunch of guys without the paper who still know what they're talkin about more than I do.

 

[coulter]

...Why does it matter that these voltages derive from a common transformer?? ... Just treat the panel as a black box where we don't know the nature of the sources. ... Give us a logical argument to support this idea. ...
V1n and V2n, as defined, are 180 degrees out of phase. It is as plain as two traces on an oscilloscope. ...

Yes it does matter to fit the model I use. No, not quite that plain to me.

edited to add: I left off the xfm primaries - and yes I knew everyone knew that

carl

 

[coulter]

You've got nothing to feel bad about Crossman...there are some pretty "scummy" Engineers out there. And there are also a bunch of guys without the paper who still know what they're talkin about more than I do.

I'd agree with all of that. with the exception i would probably say, "technically incompentent in some areas" instead of "scummy"

carl

 

[Rick Christopherson]

Paper fight:....

You can bet your "tail" that I know that there are people on this forum that know so much more than I do, that they could make me look like a fool in a matter of seconds. I am not professing anything other than that. I am publicly challenging the credentials that Rattus has already challenged that I poses. This is an issue that he brought up, but has yet to answer himself.

You guys are making me feel bad. I ain't nuthin' but a scummy construction worker.

No, Crossman. I respect you because you admit to what you do not know and you are willing to learn.

 

[rattus]

Rattus, another point could be made with the delta. If we did not ground anything, and there were no connections between the conductors I am proposing other than those in the windings themselves, , it would be entirely feasible to centertap the midpoint of ALL THREE xfmrs of the delta arrangement. Each of these "neutrals" could be used to feed loads between any other conductor of the system. There would actually be three single phase systems with their own neutral. (again. I am saying no ground connections which would cause short circuits)

And, as I look in the codebook, the definition of neutral point includes "midpoint of a single-phase portion of a three-phase delta."

Anyway, on this point, maybe it is semantics. But, the neutral is defined by the single-phase portion of the delta system, not the delta system as a whole.

I understand what you are saying.

It really is a non-issue, but there seem to be conflicting definitions. No question that the 120/240V subsystem carries a neutral.

Certainly, in a 3-wire delta system, there is no neutral.

 

[rattus]

You can bet your "tail" that I know that there are people on this forum that know so much more than I do, that they could make me look like a fool in a matter of seconds. I am not professing anything other than that. I am publicly challenging the credentials that Rattus has already challenged that I poses. This is an issue that he brought up, but has yet to answer himself.
No, Crossman. I respect you because you admit to what you do not know and you are willing to learn.

I did? I don't remember any such thing. If I did, I withdraw my challenge.

 

[coulter]

... This is an issue that he brought up, but has yet to answer himself. ...

Well, perhaps no response is a sufficient answer.

The fight certainly detracts from any technical understanding I can get. Just a suggestion.

FWIW - When someone takes a swing at me, my inclination is to swing back - hard. I'm working on weaning myself - Now I try to limit my responses to a humurous poke - and sometimes I make it.

Got to go to work - no more till way later

carl

 

[Rick Christopherson]

I did? I don't remember any such thing. If I did, I withdraw my challenge.

Yes, you did. Here it is.

Rick, I don't think you have the credentials to tell anyone else how to solve a problem, and I see no evidence that you understand AC Circuits. If you did, you would see a valid solution, and you would realize that using a different method would not change the outcome. Other statements from you lead me to believe you aren't a whiz at Physics either.

This posting was made 2 days ago....are you claiming that your memory is that bad?

 

[rattus]

Yes it does matter to fit the model I use. No, not quite that plain to me.

edited to add: I left off the xfm primaries - and yes I knew everyone knew that

carl

Carl, No one is saying that your first diagram is the way it is. If that were the case, V12 would indeed be zero.

However, your second diagram is indeed the way the world is wired, but look closely. Isn't it obvious that these voltages, MEASURED RELATIVE TO THE NEUTRAL, are inverses of each other? That is, 180 degrees out.

No one is pretending we can change the polarity markings merely by claming a phase inversion. These markings merely indicate the way the transformer is wound.

 

[rattus]

Not quite:

Not quite:

Yes, you did. Here it is.


This posting was made 2 days ago....are you claiming that your memory is that bad?

That statement was in response of your offer to educate the rest of us. I had offered valid solutions which you either ignored or misunderstood.

I could have said it differently, or not said it at all, but I did not challenge you to show your credentials. If you are still offended, consider that statement withdrawn and let's get on with a meaningful discussion.

 

[coulter]

...Isn't it obvious that these voltages, MEASURED RELATIVE TO THE NEUTRAL, are inverses of each other? That is, 180 degrees out. ...

Yes. I believe I acknowledged that in post 67.

... For the model limits you picked, what you propose will work fine. However, I find this methodology limiting. ...

carl