Can "wattage" trip a GFCI?

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In wrote:

...
It's not called that because it is ONE phase coming from the powerco and is split to make two 120Vac lines into the residence. Thus the proper term is "split phase", not 2 phase. Although I hear 2 phase a lot, I know what they'e talking about so it's NBD to me.

Nah, it's just a bunch of egos here wanting to show how much they know and hoping their guesses are right for the most part. This is a useless thread with no useful information due to the interest in egoes rather than fact. It's typical of this newsgroup for the last year or so in fact and does no one any good. Post after post is filled with guesses and by gollies from those who feel the need to confuse, not assist anyone.
HTH,
Twayne`
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Twayne wrote:

Perhaps like your "guesses and by gollies" about power factor correction capacitors, using an oven neutral for a ground and class 2 power sources which were confused and completely wrong.
This thread is excessively about semantics.
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How about this one:
http://www.allaboutcircuits.com/vol_2/chpt_9/4.html
"A pair of dots indicates like polarity.
Typically, the transformer will come with some kind of schematic diagram labeling the wire leads for primary and secondary windings. On the diagram will be a pair of dots similar to what is seen above. Sometimes dots will be omitted, but when “H” and “X” labels are used to label transformer winding wires, the subscript numbers are supposed to represent winding polarity. The “1” wires (H1 and X1) represent where the polarity-marking dots would normally be placed.
The similar placement of these dots next to the top ends of the primary and secondary windings tells us that whatever instantaneous voltage polarity seen across the primary winding will be the same as that across the secondary winding. In other words, the phase shift from primary to secondary will be zero degrees.
On the other hand, if the dots on each winding of the transformer do not match up, the phase shift will be 180o between primary and secondary, like this: (Figure below) "
Continue on in the above reference to the next section where the transformer that has two secondary windings, and keep the above discussion of phase in mind. They may not come right out and say it, but clearly you can have transformer outputs that are out of phase with each other, and hence, two distinct phases exist.
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On Sun, 23 Jan 2011 05:09:04 -0800 (PST), snipped-for-privacy@optonline.net wrote:

You can walk up the stairs, or you can walk down - and two people can walk up and down the stairs - does not make it 2 stairways.
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On Jan 23, 1:09 pm, snipped-for-privacy@snyder.on.ca wrote:

You can try to side step with cute posts all you want, but won't answer the simple questions I posed that go to the core of the issue:
Suppose I take a black box that consists of various linear circuit components and is powered by a 120V AC outlet. Inside that box, I have a common reference point. I ask students in a first year electrical engineering course lab experiment to graph the voltages at circuit points A, B, and C relative to the common reference point. I have the circuit designed so that the waveform at point B lags the one at A by 30 degrees and the waveform at point C lags the one at A by 180 degrees. I ask thefollowing questions:
What is the phase relationship between waveforms A and B?
What is the phase realtionship between waveforms A and C?
How many different voltage phases are there in the black box at points A, B, and C?
What is your answer? Is it that there are 3 phases or is that there can be only one, because it's originating from an outlet that has only one phase?
Do I need to know exactly how the voltages were generated, whether it came from a wall outlet, battery/inverter, transformer etc to answer any of those questions?
If your answer is that there are 3 phases present, then continue to the next part. I have another black box that merely consists of the 3 wire 240V service. The common reference point is the neutral, point A is one hot, point B, the other hot.
What is the phase relationship between waveforms A and B?
How many phases are present?
Note the usual disclaimer. I did not just say, nor have I said that the 240V service is commonly called a two phase service.
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snipped-for-privacy@optonline.net wrote:

I have no problem with: in-phase/out-of-phase additive/subtractive polarity or connection positive or negative polarity
To interconnect separate windings you have to know if the connection is additive or subtractive.
I have no problem with "two distinct phases" with regard to the current in the start and run windings for a single phase motor - there is a non-trivial phase angle that can vary over a wide range.
I have a problem with "two distinct phases exist" for a single phase transformer - the voltages on the distinct phases are always exactly opposite polarity. The "two distinct phases" are handled with trivial plus and minus signs (or dots). "Two phases" out of a single phase power transformer is guaranteed to cause arguments. "Two distinct phases" covers any phase angle and can lead to miscommunication.
David N's post that said: "but the 120+120$0 system we've been discussing actually is a 2-phase system, even though it's not really called that. One side is 180̊ out of phase with the other side, so by definition you have a 2-phase system."
It is, as I think almost everyone agrees now, not a "2-phase system". (David more recently writes in another newsgroup it is "truly two phase power".)
David also wrote: "Again: the output of a center-tapped transformer, whatever its use, is in fact 2 distinct and separate phases. But for some reason, it's not called that."
I agree - it is not called that. And I elaborated on why it is not called that. Like that in calculations you don't use 180 degrees out of phase. You use trivial plus and minus signs.
We have no disagreement on the physics, just the terminology. You can certainly use "180 degrees out of phase" or "different phases" if you want. IMHO it is excessively complicated, not useful, and can lead to confusion, miscommunication, and error (as by David).
The people who have objected mostly work with power systems, including multi-phase power systems. You will not likely find anyone in the power industry who considers a trivial 180 degree fixed shift a different phase.
--
bud--

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bud-- wrote:

Actually, I have no objection to saying the "A-leg" is 180 degrees out of phase with the "B-leg" either (though I would state it differently).
I have a problem with making them different "phases".
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On 1/17/2011 6:26 AM snipped-for-privacy@optonline.net spake thus:

[snip]
[snip]
Thanks; I feel vindicated.
To throw out another example, I mentioned push-pull amplifiers in my earlier reply. These are almost always preceded by a stage called a phase splitter or phase inverter, which takes a signal and splits it into two phases, one 180° from the other. Every electronics engineer in the world would agree that this stage produces two distinct phases from a single phase. Which is exactly what our center-tapped transformer does.
Again, just to make it crystal-clear, the electrical industry uses the term "2-phase power" in a very specific way that does *not* include this way of generating two phases. Nonetheless, it does generate two phases, so technically speaking it is two-phase power.
Even if you would get laughed at by the power company for asking for a 2-phase transformer.
'K?
--
Comment on quaint Usenet customs, from Usenet:

To me, the *plonk...* reminds me of the old man at the public hearing
  Click to see the full signature.
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On 1/15/2011 3:25 PM, dpb wrote:

I think you mean: - sin t

That completely sums it up for me. And better put than I could. :-)
Jeff

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dpb wrote:

>> t2=t-pi;

Above is missing one line that somehow didn't get pasted from the Matlab command window...the definition of t2--see above

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Jeff Thies wrote:

I haven't seen one. (Weren't the original Westinghouse/Tesla AC generators at Niagara falls 2-phase?)
I have seen Scott (or T connected) small 3 phase transformers that essentially convert 3-phase to 2-phase to 3-phase (2 transformers for 480/277 to 308/277).

Three phase probably uses significantly less copper to convey a given amount of power.

Three phase motors are probably cheaper than single phase starting at somewhere less than 1 HP.

You combine a 120V transformer winding with another 120V transformer winding that is in-phase to get 240V. In fact, as everyone knows, it is a single winding with a center tap.
You won't find an electrical engineer for power systems who will say 120/240V is not single phase. You are not likely to find an electrician that deals with 3-phase who says 120/240V is not single phase. Wikipedia is not likely to say 120/240 is 2-phase.
--
bud--

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A Scott-T needs two phases to get a third. One split phase won't do it.

Yes. Increased efficiency, too.

Simpler, but I doubt cheaper (volume).

Only because it's not. ;-)
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snipped-for-privacy@att.bizzzzzzzzzzzz wrote:

For a 3-phase transformer, you use 2 transformers in a Scott connection for the primary, and with a Scott connection on the secondaries. The primary is 3-phase. The secondary is also 3-phase. The voltage in the transformers is at 90 degrees - 2-phase. A disadvantage is the transformer currents are not in phase with the voltage so the transformers can't be used at their full rating. It is practical for small 3-phase transformers.

I am too lazy to look up prices (which also requires matching quality). My notes say over a 1/2 HP motor is cheaper in 3-phase. You don't need a winding that is only used to start the motor. And you don't need the start switch paraphernalia and often a capacitor. Motor control is likely more expensive.

Fans of "2-phase" could ask for a 120/240 2-phase service from their utility.
--
bud--

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Simpler, I agree. Whether or not the volume (of single-phase) motors exceeds the difference in complexity is the question. Also, I suppose, it depends on who's buying (in what quantity - inventory costs as well as manufacturing).

;-)
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On Sun, 16 Jan 2011 11:31:08 -0600, " snipped-for-privacy@att.bizzzzzzzzzzzz"

Well, all I know is I can buy 2HP 3 phase motors for considerably lower cost than 2HP single phase here in Waterloo and they are generally smaller as well. When you get to 5HP and higher, the difference REALLY becomes obvious. Not sure how 1/2 HP compares.
Also, lots of decent used 3 phase motors are available CHEAP, while good used single phase are less common (because 3 phase only burn out or need bearings, while single phase can also have starter problems, bad caps, etc - and are also more prone to burning out when starter problems occur.)
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On Sun, 16 Jan 2011 15:23:20 -0500, snipped-for-privacy@snyder.on.ca wrote:

Fractional-HP motors are what I was really thinking about. Certainly above a couple of HP the numbers go the other way. A single-phase 100HP motor would be a rare thing indeed. ;-)

A lot of those things that burn out on a fractional-HP motor are pretty easy to fix, making the motors a lot cheaper (scrap yard cheap).
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On Sun, 16 Jan 2011 15:30:48 -0600, " snipped-for-privacy@att.bizzzzzzzzzzzz"

When a 3 phase motor ends up in the scrapyard because it outlasted the machine it was on, you only need, at worst, a pair of bearings. When a single phase motor ends up in the scrapyard you likely need a $16 starting cap as well as the bearings - and may also need to cleen/repair the starting switch.
The big problem is you need a 3 phase supply to run the 3 phase motor - and outside of industrial plants 3 phase is "relatively" rare.
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On Sun, 16 Jan 2011 16:55:12 -0500, snipped-for-privacy@snyder.on.ca wrote:

$16 is still a cheap motor.

A lot of woodworkers use a three-phase motor as a rotary converter.
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Bud Would you please guide me out of this morass these folks have constructed for themselves. You know how the dry transformers that we install all the time have output voltage selection taps to compensate for the variations in utility input voltage so we still end up with 120 volts for the general purpose receptacles? What do you say we wire one with a conductor off of each voltage selection tap. Do we know have six phase or eight phase. Dam I cant keep my tongue that far out in my cheek without it starting to hurt.
I just thought of another question for the two phase crowd. How many phases on the output of a high leg center tapped phase delta transformer? By there logic it must be four. Dam my cheek is starting to hurt again! -- Tom Horne
"This alternating current stuff is just a fad. It is much too dangerous for general use." Thomas Alva Edison
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On Wed, 12 Jan 2011 20:54:48 -0600, Dean Hoffman

Ok everyone. Without any explanations included. Weigh in on the final answer. In phase or 180 out? You are allowed only yes or no. Is the sentence in question correct?
I vote no.
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