Whether you have 1 phase or 2 depends on the reference point, either the middle of the (center tapped) transformer secondary or one end. It seems normal to use the point that's grounded.
120V, 120V (2 phases, 180 deg. apart))or
120V, 240V (same phase)Some people seem to be confusing this with the single phase at the transformer primary.
That describes a 2-phase system (phases 90 degrees apart, and I don't think anyone here disagrees with that. That they do disagree with is that being 2-phase keeps anything else from being 2-phase. "2" and "phase" are WORDS, and not restricted to a single instance.
And that isn't it. It is an EXAMPLE of a 2-phase system.
It's as if the first truck you ever saw was a propane delivery truck, so you think dump trucks can't really be trucks.
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I'm not sure if it's the way you're supposed to figure it, but
240 * sin(120)is approximately 208. I haven't seen it, but have heard of large apartment buildings wired that way.
Just as if you have a person on the north pole and one on the south pole of the earth. They are standing and extend their right hand past their head. Which one is pointing up ?
If you are a space ship and can see them both. The seem to be pointing in opposit directions. So then which one is point up ?
It's been a long time since I learned to be suspicious of discontinuities like that (like that second phase being fine at 179 or
181, but ceasing to exist at 180). It's one way of knowing when a thing can't be true.
One end of the primary connects to a live wire. What is the other end connected to?
Exactly. And again, since no one will attempt to give a definition of N phase power, I'll give you what I think a sound definition is:
A power delivery method utilizing N sources that are periodic, of the same frequency, that differ in phase.
And then it becomes where do you look, what are you analyzing. If one looks at the primary side of the transformer, then clearly there is only one phase. However if you look at the secondary side, the three wires going into the house, then you have two sources, ie the the two halves of the transformer that are 180 deg out of phase with each other. Which is what that IEEE paper is about, how you have to treat it as such to analyze it. For example, if there is reactive loading on one side of the transformer, purely resistive loads on the other, then the voltage and current waveforms on one side can have a phase difference from the other side of the same transformer. That is what the professor was pointing out, in terms of how it has to be treated and analyzed.
A permit to add lights in your own house. Are you mental?
"one or the other" is not the same as 2-phase.
That's a really unusual battery, that keeps reversing polarity. Anyway, you'd just be getting one phase.
On the secondary side of the transformer, you have 2 voltage sources (both the same voltage). If the phase is the same also, you could connect both together, for more current.
That's true and it also demonstrates that when you treat the transformer as what it is, two voltage sources differing in phase, it's all covered. With phase difference of zero, you would have two voltage sources in perfect sync that could deliver current from both, like you just said. With phase difference of 180, you have two sources that deliver
120V with respect to the neutral, or 240V between the two sources. With phase difference of 90, you have Ralph's two phase from 100 years ago.
In that case, what is UP?
Look in a mirror and point to the right with your right arm. The image in the mirror is pointing to the left with its left arm, but you both are pointing in the same direction. The mirror image is not reversed left-right, it's left and right that are reversed.
As to that transformer, what is your point of reference when measuring phase?
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If you follow the law, in my township you'd need an electric permit for 1 circuit at a cost of $110.
Upon completion of the work, you'd need a one circuit inspection at an additional charge of $125
...if you follow the law, LOL.
I thought it was bad here. We only need permits for gas works, or for buildings which can be seen by neighbours. For some reason this excludes conservatories (which are classed as a temporary building?!?), garages, and sheds, as long as they are only 1 storey high. And no I didn't inform anyone when I moved my own gas main. It's MY gas main.
No people in the trade where there is life on the line use very specific terms. Blurring them to make concepts understandable for new students or homeowners is not what they choose to do.
It really depends on how fast you can flip a battery over doesn't ? See what happens when you start confusing terms.
Actually you mean when you hook your scope up in the center of the single phase winding. I can do the same thing with 2 AA cells and make it look like the plus end of one battery is actually minus.
Oh, please stop with the "life on the line' nonsense, like a discussion about phase is going to kill people. And how about answering the very simple questions I posed to Ralph:
Let's take your second example of what you say was the old two phase power, ie 90 deg phase difference, three wires with a common return. I changed the phase difference to 70 deg by rotating one of the windings on the generator. Are there still two phases there? Now I change it to 179 deg, are there still two phases there? I change it to 181, are there still two phases there? I change it to 180 deg, are there still two phases there? And how is the latter any electrically different than the
3 wire 240/120V service going into a home? Describe how I could tell from the panel in your house which of the two power sources I had supplying it, 240/120 from pole a transformer or two phase from Ralph's generator that I changed to 180 deg phase shift. How are they electrically different, how do they behave differently?
Yes, how very unreasonable to hook up a scope using the system neutral, the system reference point. Is that like an unfair magic trick? And no, it's not hooking up the scope backwards. Connect the ground clip to the SYSTEM NEUTRAL. Connect one probe to L1 you get one sine wave. Connect the other probe to L2, you get the inverse, 180 phase difference sine wave. Which of course is exactly what the power source is, two sine wave sources that are 180 out of phase with each other.
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