Well, what we think of as single phase isn't. It's actually two phase. Trader 4 posted a link to an IEEE paper in another thread. Here:
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I work with irrigation which mostly relies on three phase power. We sometimes tap power off grain bin sites which many times have "single" phase 240. We'll use a transformer to produce 480 and add a phase converter for the third phase. The converter adds one phase to the two already there to run three phase motors. It never occurred to me to think of "single" phase as actually two phase until Trader posted the link. It has to be or phase converters wouldn't make our irrigation systems run. Granted, none of this probably matters to Joe Homeowner wiring a garage light or a stove.
I just found where I actually said the joke, and, well, it's pretty clear to me that I was joking. Oh well. It's still my fault if nobody got it.
Here is the exact quote that was snipped out prior. Notice I first explained that the ground is the return path for the three 120-degrees-out-of-phase hot wires, and then I added the one sentence (with a smiley) that got me in trouble:
Apologies > I was always of the opinion that the ground was the second set of three wires.
It's not a paragraph, it's part of the same paragraph. And the part you referr "This paper will describe the modeling and analysis of the single-phase cen ter tap transformer serving 120 Volt and 240 Volt single-phase loads from a three-wire secondary."
The transformer is single phase on the primary side. The loads it drives a re single phase 120v and 240v loads. No one is saying anything different. Ho w can you ignore the elephant in the room where the author immediately befo re explicitly addresses the exact core of the issue:
"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. "
He explicitly says that TWO PHASES ARE PRESENT and they differ by 180 deg. That from an IEEE engineer presenting a peer reviewed paper at a power engineering conference.
Or an app note from an electrical eqpt manufacturer:
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"The two legs, represented by Phase A and Phase B, are
180 deg apart.
Or this white paper from another electrical eqpt manufacturer:
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Note the reference to Phase A and Phase B in the foot note to the diagram and that they are 180 deg apart. And that the diagram is clearly labeled Phase A and Phase B.
Are all of them among the confused, who know very little? I have a degree in Electrical Engineering. Other than this disagreement, is anything I've posted in these two threads incorrect? Good grief.
What exactly is your definition of phase? Because it's derived from one primary phase, you can never have more than one phase? In electrical engineering, science, math, the most basic meaning of the word phase is to express the relationship between two periodic waveforms. In this case, in a split-phase 240/120V service you have two different waveforms, they are 180 deg out of phase wit h each other and you can see it on an oscilloscope. It's every bit as real a s seeing 3 phase waveforms on a scope. The 3 phases are seperated by
120 deg, the split phases service is seperated by 180 deg. That is EXACTLY what the IEEE engineer is saying.
I don't think it really matters whether we're calling the 120 VAC lines coming into our house "single phase power" or two separate phases. Or, precisely what to call it certainly doesn't warrant the amount of time being spent arguing over what to call it.
What matters is that we understand how the wiring in our houses (including the electrical panel) works, and I don't think that part was ever in question.
Wish I could remember the details. And the people on this list are glad that I can't. But, I remember hearing one time, how the theologians of earlier generations used to write commentaries on this or that. Commentary on the parable of this or that. One theologian wrote a summation of the gospel, in such simple terms he figured it would be the do all and end all, of writings. Shortly after he published it, a lot of people wrote commen- taries on his summary.
Nestork did excellent job of shutting down the thread, and then someone has to get in one last word. And, others will write commentaries on Stormin Mormon and his religious take on the matter. Sigh.
"singlephase" distribution transformer connection as single phase because from the primary side of the transformer these connections are single phase and in the case of standard rural distribution single phase line to ground. However, with the advent of detailed circuit modeling we are beginning to see distribution modeling and analysis being accomplished past the transformer to the secondary. Which now brings into focus the reality that standard 120/240 secondary systems are not single phase line to ground systems, instead they are three 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 the secondary phases are separated by
180 degrees instead of three phases separated by
120 degrees."
Aristotle says that 4,126 angels can dance on the head of a pin.
Confucious says that incoming power in the USA in the twenty first century will be single phase.
Jesus said if thy brother offend thee, and strike thee on the phase, turn the other cheek.
Billy Graham says he's getting old, but that does not phase me very much.
Thank you. Good to see someone looked at the link and realizes what it says.
That link is from the highest credibility source you could possibly get, but aaddresses the very core of the issue:
"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."
I supplied other links to references from electrical eqpt manufacturers tha t clearly show and describe 2 phases, 180 deg out of phase with each other as well:
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So far, the other side has no references.
I'm still waiting for the definition of the meaning of phase from those that deny that the two hot legs on a split phase 240/120V service are 180 deg out of phase with each other. That is what started all this. They appear to be hung up on the fact that it's derived from a single primary phase. How it's derived doesn't change what you get, what you can see on a scope, how it drives a load, etc. You brought up an example of generating an additional phase via a transformer. Earlier I brought up another, very common example too, open delta three phase.
For most 3 phase loads, 3 transformers are used to step down from the primaries. They have 3 transformers, one connected to each of the 3 utility primary phases. So far, I think everyone agrees with that. Three phases in, three phases out. Now, for light 3 phase loads, to save the cost of an additional transformer, by using a center tap transformer, the utility can supply 3 PHASE POWER, using only two transformers, connected to only TWO of the utility primaries. The utility calls that 3 phase power. The customer calls it 3 phase, the 3 phase motors run on it, you can see 3 phases on a scope. Yet it's derived from only TWO of the utility primary phases. Two phases in, three phases out. Following the arguments of those on the other side, then that should only be called two phase power. Yet there it is,
It does warrant a response when you have some people here saying that anyone that says the you have two legs, two phases, 180 deg out of phase, "know very little or just enough to confuse themselves". And the village idiot questioning my degree in electrical engineering. I take offense to that. I've provided a link to an IEEE peer reviewed paper presented at a conference of power engineers.
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"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. "
That's from an unimpeachable source, the IEEE. I've also provided links to eqpt manufacturers, etc.
The other side, nothing but flapping gums.
That is correct. But when you start baseless personal attacks and are incapable of even defining the word "phase", then what do you expect?
Well, I *thought* I understood electricity, in that without a "loop", there would be no current.
What I *think* is the real answer, albeit it's hard grasp because the earth itself is so huge, is that there *is* a loop with the power company.
The loop starts with electrons being pulled from the ground, which then go over the three hot wires where one of those three hot phases is sent to your transformer primary, where the second lead of the transformer primary goes into the ground, which completes the circuit.
The fact that the earth is so huge that this completion of the circuit isn't even noticed back at the power company doesn't mean there isn't a loop.
It's just that the loop is one huge chunk of conductor (namely, the earth itself).
But, it's my understanding that this still completes the loop.
For example, if I lifted the transformer primary wire so that it no longer contacted the ground, that would immediately stop the current that flows back into the ground, hence breaking the loop.
Even though the ground is so big that even all the nuclear power plants in the world pumping electrons into the ground couldn't change its potential, that doesn't mean that the ground doesn't complete the circuit.
If the power company chose any other conductor other than "the" ground, then they would have to have a wire for each phase distributed.
Since the power company chose to use "the" ground as "their" ground, the way I understand it, "my" ground is connected to "their" ground, so, the electron that flows into the primary of my transformer came from the ground at the power plant, and it goes back into the ground at my house, to (theoretically) make it back to the power plant.
Of course, the ground is so big that it's like pouring a glass of water into the ocean, where that molecule eventually will make it around the earth - but the immensity of the ground should not be construed as implying there isn't a loop from the earth at the power company to the wires to my transformer primary to the earth at my transformer.
At least that's how *I* understand the typical mains power in the US.
Which one you call A and which B is arbitrary. What matters is that you wind up with the phases alternating on the breaker slots, vertically. That way with a double pole breaker, you get 240V. If they didn't alternate, you'd get 0v.
Most of the current doesn't have to flow back via the earth. You have a transformer that is connected on one phase of the primary. It serves several houses. Further down the street, there is another transformer, it is on a different phase. Even further down, there is another transformer on the third phase. The other sides of all those transformers are all tied together on the primary neutral. If those loads are equal, then the sum of the currents in the neutral is zero, you have a balanced wye configuration and the only net current flow is in the 3 primary phase wires.
He has a legitimate question. It's not clear to me why sometimes the neutral service wire is insulated, like he has. I know it's also many times uninsulated as well.
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