On Jan 16, 4:23 pm, firstname.lastname@example.org wrote:
Unbelievable. People are actually replying and answering this stupid
without apparently even realizing that the question already answered
itself. Did it not state: ""The two insulated wires each carry
120 volts, but they are 180
degrees out of phase "? Beyond that, it wants a yes or no answer to
that is mutually exclusive, ie "In phase or out?" How the hell do
you guys answer
that with a yes or no?
The problem some of you are having is understanding the difference
what something may be commonly called by those in the trade and the
concepts and definitions of systems, phase, etc.
And in the case of 240V service in your house, the answers you seek
Q What is the phase relationship of the two hots?
A They are 180deg out of phase with each other
Q Does it matter how that phase difference was achieved?
A No, from an electrical engineering perspective, we just need to look
at the voltage waveforms and current flow on the service cable. Plot
on a graph paper and you have your answer.
Q Is this commony called a two phase system?
A No. Probably because it's created by a transformer that uses one of
phases generated by the power plant.
On Mon, 17 Jan 2011 06:47:54 -0800 (PST), email@example.com wrote:
It was defined to me some 30 years ago, but what I came away with was
that it is "in phase" if the voltage and current reach peak and 0 at
the same instant. That is what I understand a single phase
transformer does. (Ignore capacitance and inductance)
What you are talking about is the relationship between voltage and
If I put capacitance or inductance in a linear system, it changes the
between the voltage and current. So, as you put it, they don't reach
zero at the same time. When plotted, the current and voltage are out
phase by a certain number of degrees. Whateve that shift is, you can
it in degrees.
The phases under discussion here are pure voltage waveforms and are
present without even having a load. With a
240V service, you have identcial sine waves which are mirror images of
each other, between either hot and neutral. Take a sine wave and
it by 180deg, ie one half cycle, and that is exactly what you have.
have two voltage waveforms that are 180 deg out of phase with each
Hook up an oscilloscope and you can see it. Yet some are arguing
then just becomes "it's just a negative", it's a case of plus and
and can no longer be described as two phases which are 180 deg out of
Yet, there they are on an oscilloscope. Maybe someone can tell us
I can see these two distinct phases on those 3 wires of the 240V
service with an oscilloscope.
With 3 phase, I could do the same thing on that service and see 3
phases, each seperated by 120 deg. Why is it that in the latter
case, those on
the other side of the argument here say there are 3 phases present,
but in the former,
there are but one, not the two on the oscilloscope? Posters dpb,
Jeff and David and myself
would describe both those services, their phases, in a consistent,
Usual disclaimer: I did not just say, nor have I ever said that a
is called a two phase service.
I have no idea where I read that thing about electrons just jiggling
in an AC circuit. Curiosity got the best of me so I snooped a bit.
These popped up: http://tinyurl.com/4pgadee
OK, that's interesting; thanks. I'd never read that explanation. (I'd
sooner trust the BPA article than that online forum that seems to have a
lot of clueless, unscientific types posting to it.)
So what they're saying is that, basically, even though electricity moves
at [about] the speed of light, electrons actually move very slowly.
But that doesn't change the fact that in both DC and AC, *current*
flows, almost instantaneously in both cases. It's just that current
doesn't necessarily coincide with electron motion.
(I have no idea now how electron and current flow actually works, but
again, that's at the quantum physics level. Us boneheaded electricians
can still go on thinking that AC currents flow, not "jiggle".)
Comment on quaint Usenet customs, from Usenet:
To me, the *plonk...* reminds me of the old man at the public hearing
It seems to me that the problem is with the GFCI, or more likely with
As mentioned elsewhere, the GFCI looks for an imbalance between the
current in the hot and neutral. If those don't cancel it is presumed a
current is flowing in the ground, and it shuts down.
My guess is that there is a fault in the grounding somewhere in the
garage and that the lamp draws enough current so the mismatch is large
enough to trip the GFCI.
I don't know much about these, so that is just supposition. If it
were me, I'd look at the neutral connections. Perhaps sub in a regular
outlet and look at the voltage drop between known good ground and
neutral. But I really don't know, but it is clear that it isn't the light!
*If it is a very old GFI he may be right. Inside of a garage there are
large temperature and humidity variations as well as fumes from gasoline and
other things that get stored there. The insulation inside of the GFI may
have degraded and there may be some internal leakage with a large load.
Change the GFI and see what happens. I suggest installing a GFI that is
rated for outdoor use. It will have a "W" or "WP" on the label.
FYI..in our latest exchange he said that he has already swapped out
the GFCI and it didn't help.
His final answer was "I no longer do much work that requires a high
wattage worklight, so I gave up chasing the problem. My underpowered
incandescent rough duty bulb is enough."
What are you going to do...
You can test a socket say, by plugging in another device. How about a
less than 1500 watts.
You can also try measuring resistance to ground on either line input
on the plug. It should be megohms or higher.
Try also working the switch. Its possible to buy breakers
with GFI's, but they are usually in the main household box.
Heck, I bought a 500 watt single tripod lamp at my local hardware for
It has a two position switch for brightness. They get some nice deals.
Also make sure ground is connected to the metal stand, but that's just
a safety issue.
On Jan 18, 7:51 pm, firstname.lastname@example.org wrote:
It may be critical to the convention of what that 240V service is
called, but it doesn't alter the fact of how many distinct voltage
are present. Going back to your example of the simple circuit with
balanced loads connected across the 240V hots, yes, in that case,
you have only one phase.
I cannot hook up an oscilloscope and see anything but one sine wave.
As soon as you introduce the neutral, now I can see TWO different sine
waves relative to the neutral, one being 180deg out of phase with the
other. That circuit can now be described as having two phases.
Suppose I take a black box that consists of various linear circuit
and is powered by a 120V AC outlet. Inside that box, I have a common
I ask students in a first year electrical engineering course lab
graph the voltages at circuit points A, B, and C relative to the
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?
Do I need to know exactly how the voltages were generated, whether
it came from a wall outlet, battery/inverter, trnasformer etc to
of those questions?
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?
If your answer is that there are 3 phases present, then continue to
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 two phase.
It's like I said earlier. If I went around telling people my
son is a homosapien, or if I referred to water as dihydrogen
oxide, it would be unusual and cause much
confusion, because a lot of people wouldn't even know what
it means. But that doesn change the fact that technically those
definitions and terminology are correct.
Also, Bud's argument asking to find a center tap transformer
manfacturer that calls their transformer two phase doesn't prove
anything. I could just as well ask to find a capacitor manufacturer
says their capacitor can generate a 90deg phase shift.
This makes no sense at all. Why do I neeed 2 seperate secondaries?
You are getting all hung up on where the power comes from. The mere
presence of two voltage waveforms that are of different phases in a
readily visible on an oscilloscope, is all that it takes to have two
On Jan 22, 3:30 pm, email@example.com wrote:
In other words, you won't answer a few basic, straightforward
questions about phase that go directly to the core of the discussion,
do so is impossible without contradicting yourself. I think those of
us on the
other side of this have answered and addressed all your questions/
with no problem.
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