I invented a 2-phase DC battery pack

Page 4 of 5  
On Tue, 3 Dec 2013 22:36:50 +0000 (UTC), snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) wrote:

We run 3-phase down most streets, too. In many places, each house has its own transformer. Three-phase makes distribution simpler but split-phase gives the flexibility that you have, using more than one phase, in a simpler manner.

Irrelevant.

Wrong. Except in rural areas, the 3-phase HV *is* distributed on each street with, at most, a few houses on each transformer. In rural areas they may only have one phase on the pole but there is a transformer there, too.
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On 12/3/2013 4:36 PM, Andrew Gabriel wrote:

It is what I attempted to convey it too few words.
If I remember right, there are bathroom outlets that are connected the same.

How does the EU get involved.
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Rules for bathroom sockets in the UK are that it must be from an isolating transformer, and restricted to (IIRC) 25W (usually restricted by a very slow acting self reset thermal fuse, or just a self-reset thermal switch on the isolating transformer). It's intended for shavers, electric toothbrushes, etc. The isolating transformer is to prevent risk of electrocution in an environment which is likely to be wet, and the person and appliance is also likely to be wet. The output is isolated and not connected to ground (which would defeat the whole object).
There's always a 120V socket and a 240V socket, simply because if you have an isolating transformer there anyway, the cost of providing an extra voltage output is negligable.
This rule has been relaxed in the latest regs to allow ordinary socket outlets providing they are at least 3 meters from a bath or shower (IIRC - haven't got the regs to hand just now). This allows for having a shower in a bedroom, for example, and having standard sockets in the rest of the bedroom.

EU has rules requiring that all member states allow free movement of people and products across borders. This prevents the UK from insisting that construction site tools must all operate on a special voltage only found in the UK, as a carpenter from, say, Italy won't have 110V tools, and thus would not be able to take up a job on a UK construction site.
In practice all UK construction sites are still 110V and all UK construction workers tools are 110V, but in theory an Italian carpenter could now turn up on site and request a 230V supply for his tools - that used to be illegal. At one point in the negotiation of this change, 110V construction site tools were to have become illegal in the UK - they were only saved because they result in far fewer construction site electrocutions than is the case in other EU countries which use 230V tools.
--
Andrew Gabriel
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On Tuesday, December 3, 2013 2:57:16 PM UTC-5, bud-- wrote:

two

y

two


No, that is most certainly *not* what the discussion was ever about. I never said it was commonly called two phase. No one else ever said it was called that either. Like the IEEE engineer that delivered the paper at the power engineering conference, I simply said that in fact from an electrical engineering perspective, there are two phases present. The references I've cited from electrical eqpt manufacturers, etc, say the same thing. They explicitly talk about two phases being present. Are they all nuts too?
I'd also point out that this whole thing started when a poster pointed out that one hot on a split-phase service is 180 deg out of phase with the other. That is what krw said was wrong, that they are not 180 deg out of phase, they are "opposites". That is about as dumb a thing as one can imagine. I've given probably 10 references now, including about as credible a refernce as you can get, a paper delivered at an IEEE c onference of power engineers, where the author/speaker, says there is a 180 deg phase relationship, that you do have two phases. He's the author of a whole bunch of very technical papers on power engineering, all published by the IEEE, a peer reviewed group. Is he and the IEEE nuts too?
http://ieeexplore.ieee.org/xpl/articleDetails.jsp?reload=true&arnumber4520128
"Which now brings into focus the reality that standard 120/240 secondary sy stems are not single phase line to ground systems, instead they are three w ire systems with two phases and one ground wires. Further, the standard 120 /240 secondary is different from the two phase primary system in that the s econdary phases are separated by 180 degrees instead of three phases separa ted by 120 degrees."
http://www.samlexamerica.com/support/documents/WhitePaper-120240VACSingleSp litPhaseandMultiWireBranchCircuits.pdf
Page 2: Explicitly talks about split-phase consisteing of two phases, A and B and that they are 180 deg opposite each other.
http://www.behlman.com/applications/AC%20basics.pdf
Says the same thing.
And I'd also note that none of those references say it's called two phase either. Just that there are in fact two phases present.
It's properly called "split-phase", everyone agrees on that. When you spli t something, can you give us an example of a case where you still have just one of those things? In quantum physics I guess, but not in the everyday world. The argument that because it's commonly referred to as single phase doesn't change what's there. It's like saying that because you call something Kleenex, it's not also correct that when you analyze it, it's a soft paper tissue. Or that because water is called water, when you correctly analyze it, it's not H20, made up of hydrogen and oxygen. From the power company's perspective, split-phase originates from one of their 3 primary phases. So, I'm guessing, that is the historical reason that it's frequently just called single phase service, to distinguish it from the other common power source, 3 phase.
And I'm still waiting for someone on the other side of this to provide their definition of the engineering term "phase". How can people make post after post, yet no one can define a very basic term? Good grief. Or to address the simple excercise in phase, where I go from what you all say is a true two phase service to split-phase, just by changing the phase difference? Split-phase either has two phases present, or else something magical happens at 180 deg, as you slowly change the phase from 90, to 120, to 179, to finally 180. How can there be two phases at every other possible phase angle, but not at 180?
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On 12/4/2013 2:49 AM, snipped-for-privacy@optonline.net wrote:

As I have responded twice already, the author is suggesting a change from how "distribution engineers" view this - that is in the first (missing) sentence. The author suggest a change to view split-phase as two phases. Where did anyone agree with him?
This source ("distribution engineers") supports my view.
Maybe we need an english teacher, not an engineer.

Thats the one with a 2-wire circuit, hot and neutral, with the hot labeled "Phase A"

For my amusement I looked at a major transformer manufacturer. http://www.eaton.com/ecm/idcplg?IdcService=GET_FILE&allowInterrupt=1&RevisionSelectionMethod=LatestReleased&Rendition=Primary&dDocName=TB00900004E
Eaton defines "Phase: Type of AC electrical circuit; usually single-phase two- or three-wire, or three-phase three- or four-wire".
I would define a meaningful use of "phase" as using the "imaginary" axis in a phasor representation. Split-phase uses just the "real" axis.
Eaton has no single phase transformers with 2 phases on the secondary.
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On Wednesday, December 4, 2013 4:01:53 PM UTC-5, bud-- wrote:

ference of power engineers, where the author/speaker, says there is a 180 d eg phase relationship, that you do have two phases. He's the author

too?

rE20128

y systems are not single phase line to ground systems, instead they are thr ee wire systems with two phases and one ground wires. Further, the standard 120/240 secondary is different from the two phase primary system in that t he secondary phases are separated by 180 degrees instead of three phases se parated by 120 degrees."

It's isn't a question of viewpoint. It's very basic electrical engineering. He clearly says that you have two phases present and that is how it needs to be correctly analyzed using electrical engineering. He doesn't say, "There really aren't two phases present, but let's pretend there are". He's saying there are two and that is how it needs to be modeled, analyzed, etc., which he does in the paper.
The fact that it's called split-phase, single phase whatever doesn't change electrical engineering. Which is why I've asked a dozen times now for your definition of the electrical engineering term "phase".

Which source is that? I don't see a cite.

Good grief. Did you even look at it? The first diagram is a 2 wire circuit. That's what you're looking at? The second diagram is split-phase 240/120V, which is what we're talking about. It shows 3 wires: PHASE A, PHASE B, and a neutral. It states:
"The two legs represented by PHASE A and PHASE B, are 180 deg apart."
I've given you several other sources that describe split-phase that say the same thing, ie that there are two phases present.

RevisionSelectionMethod=LatestReleased&Rendition=Primary&dDocName=TB0 0900004E

Sigh.... I was hoping for an engineering definition, which clearly that isn't. I'm surprised you even posted that. It's kind of like saying Planters and everyone else calls peanuts a nut. Then arguing with someone who has horticulturists describing it as the legume, Arachis hypogaea L, and saying it just isn't so.


Phase in basic electrical engineering terms is simply the relationship between two periodic waveforms, expressed in degrees. One complete cycle is 360 degs.
In the case of the power company, they generate 3 phases at the generating station. They differ by 120 deg. You have 3 phases, you can see it on a scope. At your house, they take one of those 3 phases, and via a center tap transformer, create split-phase 240/120V service. It has two phases, that differ by 180 deg. You can see it on a scope. When you split something, do you know of any examples where you stil just have one thing? The industry may refer to it as single phase, because it originates from a transformer connected to just one of their primary phases, but that doesn't change what it really is.
And where is the answer to the exercise in two phase power? I've asked that 6 times now too:
Those on the other side of this agree that two phase existed 100 years ago. They have no problem with it being called two phase, that was two phase according to them. So, that system had two phases, let's call them A and B and a neutral. Phase B was 90 deg off from phase A. Everyone OK so far?
Now, instead of having phase B be off by 90 degrees, let's make it off by 120 deg. How many phases are there now? I say two. Let's change it again, so phase B is off by 220 degrees. How many phases do we have now? I say two. Let's change it to being off by 170 deg, how many phases do we have now? I say two. And now, let's change it to be off by 180 deg. How many phases do we have now? I say two. And if it they agree that it is indeed still two, then it is in fact electrically identical to split-phase 240/120V service, so you have two phases there too.
Note that the above view of phase is 100% consistent, from a piece of paper, to circuit analysis, to the 3 phases at the generating plant, the two phase system of old, the split-phase of today. The alternate view is apparently that something magical happens at 180 deg phase difference.
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On 12/5/2013 10:30 AM, snipped-for-privacy@optonline.net wrote:

He says that is how he thinks it should be viewed, which is a change from how "distribution engineers" currently view it (first sentence).

Which I supplied, below.

Your IEEE cite, first sentence in the context of the abstract.
The author has a different view from "distribution engineers". Did "distribution engineers" change their view? Not in the abstract.
Third repetition.

Any english teachers around?

Of course. It has a single hot wire that is "phase A". It is a way of referring to the wire.

I supplied one, below.

But I supplied one, below.

It is kind of like your other references (not IEEE) that use Phase A... as a label for the wires.

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On Thursday, December 5, 2013 2:42:38 PM UTC-5, bud-- wrote:

onference of power engineers, where the author/speaker, says there is a 180 deg phase relationship, that you do have two phases. He's the author

s too?

berE20128

ary systems are not single phase line to ground systems, instead they are t hree wire systems with two phases and one ground wires. Further, the standa rd 120/240 secondary is different from the two phase primary system in that the secondary phases are separated by 180 degrees instead of three phases separated by 120 degrees."

He never uses the word "think". It's not an opinion piece. He says they have been "treated" as single phase because they originate from a single phase on the primary side, but in reality two phases are present.

That isn't an engineering definiton of phase by any stretch of the imagination. It's not even at a high school level.

He explains that the reason it's been viewed that way is because it originates from one phase of the primary. He then clearly explains how in fact there are two phases present. Which is why I've asked 15 times now for YOUR definition of the electrical engineering term phase. You can't give your own definition? Neither can anyone else on the other side of it. Instead you come up with one reference at an embarrasing level, from the glossary of a transformer catalog? That's your engineering? On my side I have a engineer who has written many highly technical papers that have been peer reviewed and published by the IEEE. He says there are two phases present and I'm sure if you asked him, like me, he could give you a definition.

Why are you deliberately looking at what is the wrong diagram instead of the second one which is the one that obviously is split-phase? Now you're resorting to basically lying instead of dealing with the issue.

And the above, which you did not respond to, is the section, complete with diagram, of EXACTLY what we're talking about. It says there are two phases, A and B present. Yet you keep harping back to the circuit that has nothing to do with the discussion. Unbelievable.

e

=1&RevisionSelectionMethod=LatestReleased&Rendition=Primary&dDocName =TB00900004E


The fact is I have multiple references, including the IEEE. I can give you the engineering definition of phase. I don't have to go look in the glossary of a transformer catalog. Hmmm. IEEE engineer paper delivered at a power engineering conference, published by the IEEE, vs an unbelievably dumb defintion from a transformer catalog. Which one should we believe?

is

Do capacitor manufacturers that sell caps call them two phase? Yet the current and voltage are out of phase in a cap too. You can see it on a scope. Just like you can see two phases present on a split-phase service.
Still waiting for an answer to the question of why two phase is two phase when it was 100 years ago and delivered via two hots and a neutral, one hot 90 deg off from the other. If it were 130 deg off would it be two phase? 160 deg off, still two phase? Then explain to us why if I make it 180 deg off, suddenly there are no longer two phases present? In my world, the IEEE world, at least two others here now who agree, there are still two. And at 180 deg, that two phase service looks electrically exactly like split-phase. In your world apparently something magic happens at 180 degrees and hence it can't be explained.
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On 12/6/2013 8:03 AM, snipped-for-privacy@optonline.net wrote:

Of course it is.
It is his opinion of how split-phase should be viewed. He contrasts it with the view of "distribution engineers".

That is the viewpoint of "distribution engineers".

That is his opinion He wants to change how "distribution engineers" view split-phase.

I didn't know phasors were taught in high school. [Note: these are not the same phasors that are used as weapons in the 21st century.]

The way "distribution engineers" view it.

In his opinion.

I did, 2 posts ago, and pointed that out in my last post.

That is not my definition. Perhaps if you learned to read...

In his opinion.

Still need - an english teacher for the paper, and also to tell trader I put up a definition of "phase".

Why can't you figure out if the piece says a single phase 2-wire circuit has "Phase A" it is a label.

And it is still there.

And it is still there.

Multiple references that use "phase A" as a label. And an IEEE paper that supports my view ("distribution engineers").
And two posts ago I put up a definition of phase.

I believe the "distribution engineers" in the paper. I didn't see where anyone supported the opinion of the author.
And a definition not from a transformer catalog.

>

Oooh... an new idea. Capacitors are 2 phase. One terminal is 90 degrees out of phase with the other?
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On Friday, December 6, 2013 3:44:48 PM UTC-5, bud-- wrote:

conference of power engineers, where the author/speaker, says there is a 1 80 deg phase relationship, that you do have two phases. He's the author

uts too?

umberE20128

ndary systems are not single phase line to ground systems, instead they are three wire systems with two phases and one ground wires. Further, the stan dard 120/240 secondary is different from the two phase primary system in th at the secondary phases are separated by 180 degrees instead of three phase s separated by 120 degrees."

as

It's as much opinion as it's opinion that water is formed from 2 hydrogen, one oxygen atoms.

It's not his opinion of how it should be viewed. He clearly states that two phases are present and that is how it has to be correctly analyzed, modeled, etc. If there were not two phases present, it would be really dumb to analyze it that way to come up with a correct and meaningful answer. And it would be pretty dumb for the IEEE, the most credible of sources, to publish a technical paper as an opinion piece. This is something anyone who has taken a first course in EE knows.
He's clearly saying that while it's been called single phase, there are in fact two phases present on the secondary side. He further says that distribution engineers have treated it as single phase, BECAUSE IT's SINGLE PHASE ON THE PRIMARY SIDE OF THE TRANSFORMER. He doesn't say that distribution engineers insist that there is only one phase present at the service panel in the house.
You apparently can't understand the difference betwen engineers casually referring to something from a limited perspective with an accurate engineering analysis of a circuit. It;s like bitching because a hortoculturist calls a peanut a legume and insisting that because it's commonly called a peanut, that's all there is to it and it's just the "opinion" of the misguided hortoculturist.

It's not a viewpoint issue. You can't magically create a phase that does not exist. And that is why you can't give your own basic definition of the engineering term phase. Funny thing. Those of us on the side of the IEEE paper can define it and define it consistently.
In fact, with regard to magic, that is what is required to make your world work. I'll get back to that later.

Just as much as it's opinion that water is made of 2 atoms of hydrogen, one water.

He said no such thing. He said that for it to be correctly analyzed in electrical engineering you have to recognize that two phases are present. And he presented that paper at a room full of power systems engineers, did they toss

I was referring to the crap definition from a tranformer catalog glossary. Is that what they used to define engineering terms where you went to school?
Regarding your phasor obfuscation, who in their right mind uses "phasors" to define phase? Phase is the beginning, the origin, you need to define that before you ever get to phasors. But if you want to draw a phasor diagram of the split-phase service, repersenting the two hot legs and their phase relationship, you have two at the panel, one for each leg, 180 deg apart. At the primary side of the transformer, you have just one.

This from the guy who uses a glossary in a transformer catalog to define phase in electrical engineering terms.

Yes, just like Planters and everyone else views a peanut as a nut. It's a commmon reference. It can be explained where it came from, why it's commonly called that. But it doesn't change the fact that when in scientific terms, it's really a legume. Your argument boils down to exactly that. Because it's commonly called single phase, that's all there can be, just one phase.
On the other side, we can tell you why it's called single phase. It's because it's single phase on the PRIMARY side of the transformer. That is where the distribution system engineers stop looking, stop caring, etc. That doesn't change the fact that there are two phases present coming out of the transformer. It's defined in electrical engineering. You can see it on a scope.

It's the only source you've cited with a definition.

Phase is not a matter of opinion. And it's not this one IEEE engineer at a power conference with an IEEE published paper. I've given you references from electrical equipment manufacturers. Not a glossary definition of phase from a catalog. Actual white papers on split-phase complete with CIRCUIT DIAGRAMS. And they say the same thing, that two phases, 180 deg different, are present.


Still need any kind of teacher for bud to help him learn. I post a detailed reference and he's incapable of realizing that the second example they talk about, where they call it split-phase and say there are two phases present, is the relevant one. Instead bud covers that up and lies, pretending that the first single wire example is all that is there.


You're just losing all credibility now. Sure, the first single wire circuit is labeled as having one phase, "Phase A". So what? That is entirely consistent with everything I've said, what the IEEE engineer says, the other references I've supplied, and those in this thread that agree with me have said.
It's the SECOND circuit that shows split-phase and describes it. It says there are TWO PHASES, Phase A and Phase B and that they are 180 deg apart. Good grief. It could not be any clearer. Yet you won't acknowledge it and instead just keep going back to the single wire circuit, with one phase that is above. Split-phase is NOT a single wire circuit.

All your credibility is gone. They don't just use Phase A as a label. They use both Phase A and Phase B. All these references talk about two phases being present and that they are 180 deg apart.
Behlman:
http://www.behlman.com/applications/AC%20basics.pdf
"The two legs, represented by Phase A and Phase B are 180 deg apart." They go on to say that since they are 180 deg apart, wiring them L-N gives 120V, L-L gives 240V.
Samlexamerica:
http://www.samlexamerica.com/support/documents/WhitePaper-120240VACSingleSp litPhaseandMultiWireBranchCircuits.pdf
"Phase of hot leg 2 (phase B) is in the opposite direction, ie 180 deg apart from hot leg 1 (phase A)."
It's as clear as can be to anyone that will look and learn.

No distribution engineers made any statements in that paper.

Which of course is a lie. I've given you many references, two I;ve posted, yet again, above. They all say two phases are present.

I'm curious. Do you have a degree in electrical engineering? If you do, I'd be embarrassed if I had to go to an tranformer glossary when asked to define phase.
And I'm still waiting for an answer to these simple excercises. They are very easy to answer for anyone that understands electrical engineering:
#1
Those on the other side of this agree that two phase existed 100 years ago. They have no problem with it being called two phase, that was two phase according to them. So, that system had two phases, let's call them A and B and a neutral. Phase B was 90 deg off from phase A. Everyone OK so far? Let's make the voltage from either phase to neutral 120V.
Now, instead of having phase B be off by 90 degrees, let's make it off by 120 deg. How many phases are there now? I say two. Let's change it again, so phase B is off by 220 degrees. How many phases do we have now? I say two. Let's change it to being off by 170 deg, how many phases do we have now? I say two. And now, let's change it to be off by 180 deg. How many phases do we have now? I say two. And if it you agree that it is indeed still two, then it is in fact absolutely electrically identical to split-phase 240/120V servic e, so you have two phases there too.
#2
We have 3 phase power coming from a power plant. Everyone agrees that is three phases. So, you have Phase A, B, C and a neutral. Phases A,B, C differ by 120 deg. Let's make the phase to neutral voltage 120V. Now lets eliminate phase C. We have Phase A, Phase B and a neutral. How many phases now? My answer: two. Let's run that into a house panel. So, we have two phases. Instead of 120 deg apart, make them 170 deg apart, or 250 deg apart. How many phases now? My answer: two. Now make them 180 deg apart. How many phases now? If your answer is two, which is should be, then what you have is indistinguishable from split-phase 120/240v service. There is no electrical difference, no test you could perform at the panel, no difference in voltages, current flow, nada.
And if your answer is just one phase, then explain the magic that just happened.
Note that the above treatment of phase is 100% consistent, from a piece of paper, to circuit analysis, to the 3 phases at the generating plant, the two phase system of old, the split-phase of today. The alternate view is apparently that something magical happens at 180 deg phase difference or else because distribution engineers commonly call something single phase, that no further analysis that shows electrically what is going on is required or even allowed.
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On 12/10/2013 9:48 AM, snipped-for-privacy@optonline.net wrote:

I haven't seen anyone recently write an engineering paper about what water was made from.
The IEEE paper is the authors opinion. It is not the same as the view of "distribution engineers".

Would that be like your source that shows a single-phase 2-wire circuit with the hot wire labeled "Phase A"? And then a split-phase circuit with "Phase A" and "Phase B"?
You have to label them something.

I agree.
The primary is single-phase. So is the secondary.

I did give a definition. At least 4 posts ago. It uses phasor math. It seems to have disappeared.

Did anyone agree with him.
And what is the point of what he said. I have no idea because I have not read the paper that was abstracted. Perhaps you have.

My definition used phasors. (It seems to have disappeared).

Phasors (or the math behind them) are used to analyze multi-phase circuits.

Both on the "real" axis which is trivial and does not require phasor math.

I thought Danny might be reading.

Distribution engineers are not concerned about power delivery up to the customer? News to me.

The 2-wire example shows "Phase A" is used as a label.

They said there was a "Phase A" with only 2 wires?

So I can not conclude they have been convinced by the paper.

I said (still quoted above) my definition was not from a transformer manufacturer.
I defined "phase" by use of the tool that is used to analyze multiple phases - phasors. (My definition seems to have disappeared).
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What you label them may depend on context. An electrician might label three wires L1, L2 and N.
Fred
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On 03/12/2013 9:58 AM, Andrew Gabriel wrote:

Any supply with two voltages which are not in phase can be considered 2 phase (3 or 4 wires). "Balanced" 2 phase, mathematically speaking (where for equal loads on each phase such that the sum of the currents is 0), will have a phase difference of 180 degrees - as in the 3 wire 120/240V system. This is not generally called 2 phase in North America where it is commonly used. "2 phase" generally refers to the 2 phase 90 degree shift system (sum of currents will not be 0) which, for motors, has the advantage that, as for 3 phase, a rotating field with ideally no pulsations is produced. Such motors are not common-no advantage in general with respect to 3 phase motors. They have been used as control motors in the 40's-80's.
With regard to comparative practices in distribution-this is a kettle of fish with pros and cons either way which were determined by (sometimes poor) choices made over 100 years ago. Practice depends on the past as well as factors such as housing styles, lot sizes, peak and average demands, price of copper, etc with compatibility with the past being a major factor. While, in many places 3 phases are run down each street, in many areas only a single phase is used. In my district a single HV phase is run underground supplying several pad mounted transformers- each feeding a few houses. Heavy air conditioning loads are not a concern.
--
Don Kelly
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On Wednesday, December 4, 2013 6:12:42 PM UTC-5, Don Kelly wrote:

Thank you. That's consistent with what I've been saying. It's also what the paper delivered at the IEEE conference on power engineering that I've cited says. The only part I would disagree with is that there is no reqt that it be balanced. If it's not balanced, you still have two phases,, 180 deg off, you also have current flowing in the neutral.
This is not generally called 2 phase in North America

I agree with that too. I've said from the beginning that the 240/120V is commonly referred to as split-phase.
"2 phase" generally refers to the 2 phase

Those arguing the other side of this, accept the two phase system that was used 100 years ago for awhile as being two phase. I've presented a simple learning exercise that no one will address. With that two phase distribution system, we had two phases, A and B and a neutral. B phase is 90 deg off from A. Everyone I believe here agrees that two phases are present. So, let's change the phase to being off by 120 deg. Still two phases? I think we agree the answer is yes. Make it 280 deg off, it's still two phase? So, if we now make it 180 deg off, how many phases are there? I think you and I agree there are still two, unless some magic happens. And if the power source voltages are 120V, then at that point what you have is identical to 240/120V split phase at the panel. You could not tell them apart. Neither can the electrons. That is what is there, no matter what anyone calls it.

Agree with that too.

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On 12/03/2013 11:07 AM, bud-- wrote:

Only when the centertap is your reference point.
Maybe a 240V-only appliance (no neutral) is adding to the confusion?
I've seen a cable that gets 120V/240V form two small generators (which each produce only 120V). Do you think that makes a difference in how many phases you have?
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On Tuesday, December 3, 2013 3:06:36 PM UTC-5, sam E wrote:

You mean the centertap that is tied to the neutral and earthed? The zero potential point for all 120V loads? THAT reference point? It's the most logical reference point when analyzing the system in question. It's not like someone is talking about using Mars as a system reference point.

No confusion here.

Not much to go on there. But depending on the number of conductors, and how it's tied together, if at all, whether the generators are running in synch or not, then sure it makes a big difference in how many phases are present.
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The above post and other replies indicate that knowledge is more important than jargon. In terms of poly phase jargon, think of a symmetrical 4-phase system with neutral. What we call 2-phase really is a subsystem of two adjacent phases. Two opposite phases give you an Edison system. You can get other such combinations.
In principle, as long as you have at least two phases other than completely in-phase (three or four wires) or completely out of phase, you can use transformer combinations to give you any phase combination you like. The Scott T-connection happens to be the one that converts between 3-phase and 2-phase (adjacent phases of a 4-phase) system.
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On 12/3/2013 6:28 PM, Salmon Egg wrote:

The specific question is whether in US distribution, split phase 240/120V has "2 phases", phase A and phase B? Is the centertapped secondary "single phase"? When "phase B" is negative "phase A" does it make sense to talk about 2 phases?

Relatively small 480/277V to 208/120V wye transformers sometimes use 2 transformers with a Scott connection. The transformers operate at true 2-phase.
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You are in fact exactly correct.
If you have three distinct conductors that are not connected to each other, it is defined as a 2 phase system.
Between any two conductors there is just one phase. Hence if any one of the three conductors is labeled as "Neutral", the other two are Phase 1 and Phase 2. (If there are 40 conductors, there are 39 phases.)
The magic about 180 degree phase shift is not really magic. No matter what the phase relationship is, there is a single phase between any two conductors. Of course with a two phase system the voltage between the two non-neutral conductors will be greatest if the phase relationships to neutral are 180 degrees different. It will be minimum of course if the phase relationships are 0 degrees.
The same significance for a three phase system occurs of course with 120 degree phase relationships.
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On Wednesday, December 4, 2013 12:25:53 AM UTC-5, Floyd L. Davidson wrote:

Thank you. There are now at least 3 of us here that agree.
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