On Saturday, November 16, 2013 4:28:26 PM UTC-5, Mark Lloyd wrote:
I agree. They are hung up on the fact that in an electrical
power distribution system, it isn't referred to as two phase.
But it is called "split phase", and when you split something,
well it seems you wind up with more than just one.
I would not call the electrical service two phase, as I
think someone here might have, but in
fact you do have two AC waveforms present that are 180 deg
out of phase with each other.
You could make the more general case of a "box"
that you put a sine wave into and get various sine waves
out of. They can each be described in terms of their
frequency, amplitude, and phase relationships to the
original and each other. You could have one, two, three,
10 different phases, all derived from one input.
Are they going to say that if one of them is 180 deg
out of phase with the input, that it's not correct to
say that? You can only call it the "opposite"?
"A split-phase electricity distribution system is a three-wire
single-phase distribution system."
Everyone working with power will call this a single-phase system.
Talking about 2 phases tends to confuse things. People working with
power are not likely to talk about 2 phases in what is clearly a single
phase system. I have most often heard the 2 different hots referred to
A "phase" that is always simply the negative of the other "phase" (the
same as 180 degrees out of phase) is meaningless.
Talking about phase relationships is entirely reasonable.
There is a specifically defined 2-phase system. It is not 180 degrees apart.
On Sunday, November 17, 2013 1:16:58 PM UTC-5, bud-- wrote:
You left out what follows:
"The two halves are 180 degrees apart with respect to center point."
It's also split phase. When you split something, do you still
only have one? Cite me an example.
Only if you don't understand the issues.
People working with
It's no more meaningless than a phase difference of 120 deg, 90 deg
or any other difference. It is what it is. If you didn't have a
180 deg difference, you couldn't support 120V and 240V with those
And that was what started this when it was stated
that the two hots on a 240V circuit have a 180 deg
phase difference. It of course is true. You can hook up
a scope and see it. But KRW insists that it can't be
called a 180 deg phase difference, it has to be called
"opposite", which makes no sense.
I agree with that. But again, the post that started all this did not call it a "2 phase system". The observation was simply made that the two hots in a 240V connection are 180 deg out of phase with each other. Actually, I think the
poster made the error of saying they were 120 deg apart, but that was
No, it's not meaningless. That's what it is. It's off the opposite
side of the transformer so *is* a negative.
When there is a phase relationship, it is. In the case of an Edison
connection there isn't, between the two legs. They're opposites. If
you cut the power to the transformer, both legs will disappear
together. There will not be a pi difference. If there is a line
distortion, it will appear at the SAME time on both legs, but opposite
WRT each other. There will not be a phase difference. Saying there
is, is often slang but it just adds confusion, as you point out.
Saying that there are two phases (in an Edison circuit) confuses the
issue completely. There simply aren't. There is a reason they're
known as "legs", not "phases".
Right. The only useful two-phase system I've seen has them 90degrees
On Sat, 16 Nov 2013 10:50:51 -0800, firstname.lastname@example.org wrote:
I'm pretty sure I learned, long ago, that they're 120 degrees
out of phase with each other.
The reason, IIRC, has to do with the fact that they generate
electricity with three coils. And *those* three coils are wound
symmetrically (i.e., in a Y or delta) which makes them 120 degrees
out of sync.
So, each of the three wires coming out of the power company
(which are the three wires on the poles along the street) are
120 degrees out of sync (if I'm correct).
You only get *two* of those wires going into your house.
But they're still 120 degrees out of sync (AFAIK).
Besides, if they were 180 degrees out of sync, what would
the third wire be on that pole?
On Sat, 16 Nov 2013 20:04:33 +0000 (UTC), Danny D'Amico
Nope. If you must assign a phase relationship (though it's
technically wrong) it would be 180 degrees. The phases in a
three-phase system are 120 degrees apart. Remember, a circle is 360
degrees (what happened to metric?).
Yes, the generators are three-phase, as is the distribution system.
So far, so good.
Nope, you only get one, and that one is split in half, using a
center-tapped transformer (center goes to ground/neutral).
You only see one of the three. Your neighbor might be 120degrees from
you (on another leg of the three phases) but you can't see that.
I was always told that base 60 allowed the Babylonians to
divide by the most numbers (1,2,3,4,5,6).
As I understand it, the Babylonians created the 360 degree circle
by starting from pie sections.
BASE 16 didn't work for them:
a) If you split a pie in half (vertically), you get 2 parts.
b) If you split that in half (horizontally), you get 4 parts.
c) If you split that yet again in half (with an "X") you get 8 parts.
d) If you keep doing that, you get 16 parts
e) This goes on depending on when you want to stop.
16 is dividable by 1,2,&4.
But, if you split into 12 parts instead of 16, you can now divide
by more things, i.e., you can divide 12 by 1,2,3,4,&6.
If you keep dividing, your 12 becomes 60, and now you can divide
by 1,2,3,4,5,&6 (and a few more).
So, the clock, I'm told, became 12 hours and 60 minutes.
How that 60 minutes multiplied by 6 to 360 degrees, I'm told, is just
a matter of having better granularity.
So, if I understand what I really didn't understand, base 60
was merely more dividable by things than any other base the Babylonians
could come up with.
But, I could be wrong because they came up with the Metric system for
a reason ...
If it only happens when you turn it on, it wouldn't be static build up.
That would have dissipated while it was off.
I'm wondering about some kind of misalignment or wearing out in a
two-pole switch. If one side of the 240 is energized ten milliseconds
before the other, AND that side is shorted to the shell, AND the shell
is not grounded but the vent hose _is_, then this could happen.
And that would be dangerous, obviously. Call a pro. Happy Halloween.
“Brigham Young agrees to confine himself to one woman,
This looks like a 3 wire power cord. You need to unplug the dryer and open
up the back where the wire goes in. Look and there will be 3 terminals the
power wire hooks to. It will probably be the middle wire that is the
neutral and there should be a strap going from there to the frame of the
While the dryer is open look around for any black or burnt areas near wires
or the internal electrical parts.
Wrong! Two hots and a grounded conductor (neutral/white). These types of
plugs are often referred as a 120/240. Meaning that it provides both voltages
to the device. The new 4-wire plugs do the same thing, but have a dedicated
grounding conductor for fault purposes.
As per code, a grounding conductor shall "never" carry any current unless
a fault is present; and the only purpose for carrying this current is to
trip the breaker. The other purpose of a grounding conductor is to equalize
the potential of attached devices to ground, thereby reducing, but not eliminating,
the risk of shock.
(it is possible that the service is 110/220)
I could not tell what the other end of that wire is doing, and
assumed that it was not terminated. If, by chance, it is affixed
someplace else, make a jumper wire that will go under that screw
and terminate it on the center terminal.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.