T
T.M.Haja Sahib
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Can't we try X-Y mode of operation in your scope?
Why is residential wiring known as single phase?
- Thread starter TimWA
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You'd still have the problem of the two grounds.
I thought maybe you could use a isolation transformer. But that won't work either because like you said
the scope commons are all tied togethet.
When you hook scope channel#2 up you would cause this scope to flat line. But it shouldn't smoke it, that is
with the isolation transformer. It would be the same thing as touching the red and black lead together on the #2 channel.
They do make special scopes you can do this with.
But I don't think its unecessary, most on here realize it would show two sines in sync ,peak and trough also in sync.
the scope commons are all tied togethet.
When you hook scope channel#2 up you would cause this scope to flat line. But it shouldn't smoke it, that is
with the isolation transformer. It would be the same thing as touching the red and black lead together on the #2 channel.
They do make special scopes you can do this with.
But I don't think its unecessary, most on here realize it would show two sines in sync ,peak and trough also in sync.
Yes, you can get scopes with isolated inputs and I have used them on occasion.
Tend to be a bit pricey and somewhat limited bandwidth.
Why?
Why?
Well you can. Hook probes A and B on L1 say, ground clips to neutral. Then invert trace B. But why would you want to do this in the first place?
Why?
Well you can. Hook probes A and B on L1 say, ground clips to neutral. Then invert trace B. But why would you want to do this in the first place?
T
T.M.Haja Sahib
Guest
Because Bes does not admit the existence of voltages V1n and Vn2 as he does with V1n and V2n!
Ronald, the signal you see on the screen goes through amplifiers anyway, so why quibble about another inversion?
As for showing V1 and V2, these are NOT inverted. What you see is what is there. The voltages on L1 and L2.
To prove, by sleight of hand, that you have actually got two phases from one winding maybe?
Maybe above I should have said deflection plates?
I'm really not that familiar with scopes.
If I'm in error please correct me.
So how come Besoeker gets to make up terms like anti-phase and I can't use physics terms like apparent?
Van and Vbn are NOT in anti-phase. They are the two ends of a teeter-totter and your scope is sitting in the middle.
They move together, they lead together, they lag together, and they are just the two ends of a 240V gradient from one end to the other. With effort you can distort one leg or the other but not without impacting the other leg in a reactive manner. Because in the end, they are just one single phase of 240Vac running between Van to Vbn no matter how you cross your eyes to look at them. This is a classic voltage divider not a phase inverter.
So show me this on your scope. Lets add points to the secondary coil. A(V1 @ -120), C(V3 @ -60), N(N @ 0), D(V4 @ 60), B(V2 @ 120). I've added C & D at the quarter marks. For convenience I've noted the voltages in reference to a center-tap ground defined at 0V. Per your scope NC, NA, CA are <180 while ND, NB, DB are <0.
Now remove that ground tie on your scope, cause it's really there to keep you from getting shocked on the case, and put the reference lead on point C. Like magic, NC does a flip-flop and is magically in-phase with NB according to your scope. Yet nothing in the circuit has actually changed. Except your scope now reads 60/180 with only CA being <180.
So how come Besoeker gets to make up terms like anti-phase and I can't use physics terms like apparent?
Van and Vbn are NOT in anti-phase.{/quote]
Yet this how Van and Vbn appear when measured on a common time base.
I'd call that anti-phase.
You can call it bushels per acre if you want.
Don't remember saying that. Refresh my aging memory.
Modern scopes use deflection plates, but they are driven by sophisticated amplifiers, and that is where the invert switch is located.
For that matter, they may be using flat screen displays today.
Oh, I'm flexible and adaptive enough to accept anti-phase. Or we can go with bushels per acre if my acceptance is not acceptable.
As anti-phase, this how Van and Vbn appear when measured on a common time base.
Neither I, nor Jim, nor Rick, nor Rbalex, nor any of several others have disagreed that, to use your words, the two legs appear to be in anti-phase on your scope. Neither do I, and I presume the others as well, disagree that it can be used in that manner for many, many purposes. And as Mivey and I finally came to agreement in a prior thread, unless there is a compelling need to understand otherwise then feel free to call them opposing phases.
The question on this thread was "Why is residential wiring known as single phase?". The question was undoubtedly asked for the same reason you keep defending, and no one is really questioning. When metered or scoped it appears to be two opposing phases. And when used it works like two opposing phases. So why, when it quacks like a duck and looks like a duck is it not called a duck?
To properly answer the question you have to investigate the things that make single-phase different from two opposing phases. There are real differences. But your scope setup will never show them. The test I gave you in the prior post establishes a different time base. It shows a different result. It demonstrates that when you change test conditions then you see different results. But the question isn't "What does residential wiring appear to be?" or "How can residential wiring be used?" rather it asks why it's called what it's called.
I believe I'm the one that started using the term apparent in the other thread. That was worth maybe 100 posts all by itself as peeps objected to its usage. Apparently borrowing a scientific term from a different science is considered taboo. :ashamed:
mivey
Senior Member
The different pulses are available because AC has no set positive direction. We can choose to use whichever direction we need to provide a positive pulse.
One problem is in what we call a phase. There is no clear use anymore, but what is clear is that the circuit has three voltages, two small and one large, and these can be used in either direction because AC is bi-directional. There is no set "correct" direction. The positive direction is a choice we make when using the voltages. The "technique" is the direction choice we make and does not change the fact that the voltages produced can be used either way. It also does not change the fact that the physical forces in the transformer are working in phase (there goes the use of "phase" again).
But the physical forces in the single winding are the exact same as those you get from two sources that are physically displaced by 180?. That shows that there is a disconnect between the creation method and what we take from the source, not a dependence as you suppose.
"In phase" again being dependent on definitions and assumptions. You will find that the "power waveforms" in Besoeker's circuit are not "in phase". In Besoeker's circuit, the power flows to the load on opposite halves of the AC cycle for each half of the circuit.
In the residential circuit, the "power waveform" will naturally be "in phase" because real power flows to the load on both halves of the cycle. That would also be the case whether the sources had a 0? displacement or were physically displaced by 180?. No difference. AC is bi-directional and a circuit like Besoeker's makes it clear that the voltages can be used either way and that they do not have to be the same for both halves. Our assignment of direction is the issue.
There is no "forward" and "backward". Our assignment of these designations is the whole problem. AC is b-directional and there is no "correct" direction. Each voltage can be used with either direction providing providing a positive "push of force".
At best that use of the word "phase" is slang anyway in light of the only technically correct definition of "phase". There are really just too many uses to reach a consensus on the term. What we should be able to agree on is the physical nature of the voltages. In the winding halves, the "forces" are synchronized with normal loads. In using the "forces" provided, we can use them synchronized or not, as Besoeker has shown (and the forces in the windings would not be synchronized either). As pfalcon recognizes, the forces in the source vs the usage of the forces is the "line in the sand" so to speak.
But don't forget inversion means to change the polarity not shift it in time.
There is no time shift in a 3-phase generator either. All voltages begin at the same time.
mivey
Senior Member
Unless I missed something, you should not have a double "?". You have u ? v = u ? (? 180). I think it should be (modifying your post):
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