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#127233 - 05/12/01 09:10 PM 180 degrees out of phase
Anonymous
Unregistered


In a thread on proofreading, sparky66wv wrote:
>So you're telling me that when you hook 240V up to an oscilloscope that you will see two
>independent sine waves 180 degrees apart,
Correct.

>or will it look just like a 120V sine wave with twice the amplitude?
No.
>>It's not like one is +120 V and the other -120 V.
>Precisely...that would be 180 degrees out of phase and produce 0 volts.
You are a funny guy!

Of course they cancel when combined! That's why nothing flows on the neutral.

But the potential between them before they are combined is 240 V RMS.


>Got to admit you have something there with the 6 and 9 phase thing, although lag was
>mentioned to be more of a factor there.
Okay.


> Waves 180 degrees apart will cancel each other out assuming everything else is equal.
Yes! And this is why 240 V works so well!

They do cancel... but after going through the load and having their energy extracted.


> Please do not attempt to change the laws of physics to support your arguments.
No, I won't.

The thing is, you have supported my argument without realizing it yet.

You already are quite aware that the two poles of 240 V do cancel and no neutral is needed. And when 240 V is used asymmetrically, only the imbalnce flows on the neutral.

You KNOW this already.
You ALREADY know this.

>Thank you.
YOU are welcome.


> BTW, if you had been as observant as you think you are being, you would have noticed that my post explaining 120/240V systems was cut and pasted from another post. Pardon me for not editing out anything redundant.

It's not that it was redundant, it was overkill for a horse book.


> Oh yes, and I've learned that it is better to let people think you're dumber than you really are rather than the other way around.
Then why are you thinking that I am dumber than I really am??


> Oh yes, and if I had failed to mention the "natural grey" part, you seem like the type that
> would have jumped all over that too.
For a horse book? No way!!!

I think natural grey is being deleted from the NEC. I won't miss it in the least.

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#127234 - 05/12/01 10:44 PM Re: 180 degrees out of phase
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
Let's try to put out the flames on this 180 degree on 1 phase thing, since my Asbestos Monitor is overheating

If looking at it that way makes more sense to anyone, then by all means - feel free to figure it that way. No harm no foul! That wouldn't make any installation dangerous in any way, so as far as potential damage being done by viewing it that way, only Calculus heads and Electrical Engineers get hurt by flying inaccuracies - egos heal quite rapidly, compared to human flesh.

Maybe I could toss in a real quick and dirty reason why the 180 thing is not proper theory, then just leave it at that - as this is really something that doesn't deserve so much attention.

Example:

3 phase sine waves on a scope's display [or in either a wave diagram graph, or using drawn vectors].
3 separate phasors [waves], separated by 120 electrical degrees in generator rotation time.
What are we referring to here??? Think this one out, because it will completely unmask the 1 phase thing.

We are looking at the flow of each individual phasor [or wave] and viewing the current flow in only one relative polarity.
Simply we are looking at only one conductor, but there's an equal, but opposite thing happening on the opposite end of the coil [transformer or generator] that the waveform [current] is coming from. This is happening as well on the remaining two coils in the 3 phase output.
In other words, for the one wave you visualize coming from the coil, it's current is being teeter-tottered - or bounced back and forth through the coil.
When one side of the coil comes out of Peak + direction and hits the zero line, the opposite side of the coil starts at zero line, then rises to peak +
There's no way to place these two items in a 180 degree lag or lead. They are of the same origin. Very simple Calculus here.

If that wasn't true, would we still call this 3 phase?? that would make all 3 phase systems 6 phase.

Take 2 of the 3 phase coils away, and you have 1 phase. The exact same follows on the 1 phase coil - it has only one phase [phasor, wave, sine/cosine, or vector] - regardless of how many wires are tapped off the secondary coil, or how many separate secondaries there are. Primary input is only one stand alone phase - even if derived from 3 phase power. It can only create a single flowing magnetic current in the core - it goes in one direction, stops, then flows the other way.

Polyphase transformers / generators can accomplish what appears to be a six or nine phase output from only having three phase input - mainly because they are polyphase core/coils - with polyphase inputs - not just a single stand alone phasor / vector.

Multi secondaries could easilly produce 6 and / or 9 phase outputs, since coil windings and relative polarity on those coil windings can accomplish leads/lags in secondary output currents - differing from the Peaks or zero crossings times on the other set of coils [set of coils meaning the other 3 phase secondary, which is isolated from it].

Running one secondary through Capacitors would definitely create an offset in peak/zero crossing phase time - compared to another phase.
Delta vs Wye with precise polarity points, wound in a lead/lag fashion can accomplish 6 phase output - hence the 6 phase transformer and motor.
6 phase motors will have 6 coils connected in either double delta or double wye fashion.

The main point of the 6 and 9 phase Rectifier Transformers is to push a "pseudo high frequency" into a DC converter. Thus the converter will need separate "Diode Trios" for each set of 3 phase inputs. If these have sufficent phase time lags/leads with the other sets respectively, the end result of DC entering the input of the filter will have a very much smoother and less choppier DC, due to the Hz leaving a ripple on uppermost peaks being more like 1080 Hz, rather than simply 360 Hz from straight 3 phase, or 120 Hz from single phase.


I invite all critisism on the above text - but please explore all options first [verify your claims with hard evidence from several publications {books}, then use them as quotes when replying with any disputed facts].

Open to all suggestions.

Scott SET
_________________________
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

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#127235 - 05/13/01 04:16 AM Re: 180 degrees out of phase
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
Scott;
allow me a Q please,

Are you describing on any given time line ( what we draw as 0 for sine waves) what can (or cannot)exist simutaniously???


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#127236 - 05/13/01 07:46 AM Re: 180 degrees out of phase
sparky66wv Offline
Member

Registered: 11/17/00
Posts: 2339
Loc: West Virginia
So can I think of the 9V battery that powers my trusty TI30 calculator (circa 1979, still works too!) as an infinitely phased AC source as long as that makes more sense to me? Am I allowed to preach such unorthodox theories to unsuspecting laymen on the assumption that it will make more sense to them too?
_________________________
-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI

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#127237 - 05/13/01 09:44 AM Re: 180 degrees out of phase
golf junkie Offline
Member

Registered: 04/22/01
Posts: 511
Loc: York, NE
...9V battery that powers my trusty TI30 calculator....as an infinitely phased AC source as long as that makes more sense to me?
Actually, if you look at the fourier series for DC there is some basis for this. But, why make anything so simple, so complex?

Am I allowed to preach such unorthodox theories to unsuspecting laymen on the assumption that it will make more sense to them too?

Depends....Is the purpose to educate, or to impress others with your knowledge???

GJ

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#127238 - 05/13/01 01:17 PM Re: 180 degrees out of phase
sparky66wv Offline
Member

Registered: 11/17/00
Posts: 2339
Loc: West Virginia
If this thread had continued at its original location... (proofreading thread) then my questions would appear more logical.

Dspark was the first to mention the "out of phase" idea concerning 120/240V systems.
It was in a thread intended to proofread a document intended for the laymen.

After the "out of phase" thing was mentioned, mainly by my fault, the original intent of the thread digressed to this one.

I mentioned the infinite phase AC to describe DC systems tongue-in-cheek to prove my point of unnecessary complexity to make one sound superior to others.

GJ couldn't have stated my point better.

[This message has been edited by sparky66wv (edited 05-13-2001).]
_________________________
-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI

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#127239 - 05/14/01 03:30 PM Re: 180 degrees out of phase
Anonymous
Unregistered


 Quote:
When one side of the coil comes out of Peak + direction and hits the zero line, the opposite side of the coil starts at zero line, then rises to peak +.
There's no way to place these two items in a 180 degree lag or lead. They are of the same origin.


I agree with that. I wasn't say that either led or lagged the other.

They are simultaneously occurring, 180 degrees apart wave forms.

But they are 180 degrees apart.


May I ask you to describe, if you know (and it appears that it should be knowable, see below), with respect to the input waveform, is one 90 degrees ahead and one 90 degrees behind, or what?

For this scenario, I have my oscilloscope at the transformer and I am displaying all three waveforms in parallel.

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#127240 - 05/14/01 08:59 PM Re: 180 degrees out of phase
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
Steve,
In reference to your Q:
[Are you describing on any given time line ( what we draw as 0 for sine waves) what can (or cannot)exist simutaniously???]

Not too sure exactly what you're describing here [my fault, not yours!! my mind is a little tiny thing ], so let me take a stab at an interpretation:

The current in one coil of the generating device [or xformer] will travel in one direction, stop at zero, then reverse direction, once again stoping at zero. Zero refers to the point on the generator when the rotor's field is at a point where there's no magnetic induction imposed on the coil, so current flow stops.

Best way to visualize the current flowing in a coil is to completely drop the wave thought [don't look at it as a wave], and instead just visualize the current flowing back and forth in a coil.

This will help describe phase displacements and why the currents of a coil are of the same origin.

Use the idea of one coil, place it horizontal [on the "X" axis in nerd talk], then mentally "copy and paste" a copy of that coil in a 120 degree rotation from the X axis.
Copy/paste another copy of the newly placed coil and make it 120 degrees in rotation from the 2nd coil [use a mental protractor for this one ].
You now have the basis of a Delta 3 phase [polyphase] setup.
Now insert a rotating magnet in the center of the delta - make the rotating magnet have a + pole on 1/2 the rotation, and a - pole on the other 1/2 - so they are facing the coils.

Spin the magnet and visualize the way it will cut magnetic fields across the coils.

We now have 3 independent phases [and looking at it in the wave format - even though it's a no-no right now, there's 3 wave forms with a 120 degree offset].

If we remove one coil and rotate one of the remaining 2 coils so that it's 90 degrees from the other coil, we now have a 2 phase system. We will now have 2 independent phases [and waves ] with a 90 degree time lag between them.

If we remove one more coil, that leaves only one coil, and we now have a 1 phase system. Since there's no other phase coils except this one, it's no longer a polyphase system - so there's only one independent phase [and wave ].

Hopefully all this baloney is somewhat in the area of what you are asking.


Dspark,
In reference to your Q:

[May I ask you to describe, if you know (and it appears that it should be knowable, see below), with respect to the input waveform, is one 90 degrees ahead and one 90 degrees behind, or what?
For this scenario, I have my oscilloscope at the transformer and I am displaying all three waveforms in parallel.]

From your description, it appears that you are describing a 3 phase wave form [from the 3 waves on the scope's display].

To have 3 waves and do something with all 3 of them, they could not be 90 degrees offset. One would fall into another when they become 180 degrees offset [one at + peak, another at - peak]. Here, the peak falls into the valley, which cancels the amplitudes of the effected waves.
The one at 90 degrees will still be working, so in this case we would have 2 coils that produce nothing between them selves [each other], but will produce to the coil at 90 degrees.
That would be in fact a 2 phase system, since only 2 phases can produce wave forms [only 2 phases can produce an output current].

This arrangement needs to have a 120 degree offset, so all 3 coils can produce waves [currents].

Take a brief browse over the above text I refered to Steve [Sparky], in this message and see if that also covers your Q.

Once again, I'm not exactly sure if I have addressed your question in the manner that you indended [did I understand it correctly??], so I hope to have explained things here with as much respect to your questions.

Let me know if I'm missing everything here.

Scott SET - the micro brain / tiny mind guy
_________________________
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

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#127241 - 05/14/01 09:33 PM Re: 180 degrees out of phase
Anonymous
Unregistered


 Quote:
Spin the magnet and visualize the way it will cut magnetic fields across the coils.
This is a great way to visualize a delta!


 Quote:
If we remove one coil and rotate one of the remaining 2 coils so that it's 90 degrees from the other coil
Okay!


 Quote:
If we remove one more coil, that leaves only one coil

Okay. This explains why the opposite poles are 180 degrees apart. One is near the north pole of the magnet when the other is near the south pole. I'm fine with all of this. You didn't mention that the magnet is rotating 60 times per second. Anyway, I think it is a great visualization. Now if you would just tell us how to apply it to a Wye configuration, I'd be set.

>>May I ask you to describe, if you know (and it appears that it should be knowable, see below), with respect to the input waveform, is one 90 degrees ahead and one 90 degrees behind, or what?
For this scenario, I have my oscilloscope at the transformer and I am displaying all three waveforms in parallel.]


>From your description, it appears that you are describing a 3 phase wave form.

No, I was not. So please let me try again.

>To have 3 waves and do something with all 3 of them, they could not be 90 degrees offset. One would fall into another when they become 180 degrees offset [one at + peak, another at - peak].
Have you never seen a 'scope that could display waveforms from three inputs in parallel, i.e., as if you had a separate scope for each input?

Given the the primary input (Epri) to a transformer is a single phase and its other terminal is connected to ground, and that the secondary windings are Ea, Eb, and a center tapped neutral and otherwise unloaded.

I wish to compare the phase shift between Ea and Eb. I will see that they are 180 degrees apart. Now I compare the phase shift of Ea with respect to Epri. Are they in sync? 90 degrees apart?


But if you wish, you can forget the 'scopes and relate this back to your example with the rotating magnet... Let's assume that your virtual magnet is being driven by a primary coil... How does the orientation of the virtual magnet map between primary and secondary?

If you tell me this, I think I can figure out the phase shifts myself.

What has me stumped at the moment is that if I actually built this device, I could offset the alignment of the primary and secondary by any arbitrary amount.

But when it is constructed from transformers with stationary cores, I am guessing that perhaps one of the corners on the primary side will have a low to high crossing 0 at the same time one of the corners on the secondary side is doing the same thing. There's the old intuition again.

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#127242 - 05/15/01 03:14 AM Re: 180 degrees out of phase
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
whew! i am blown away! i must point out there is certainly no lack of detail in your responses Scott!

My comment of the time line , that was how i was taught. It's simply a horizontal line, that's all. It's also the 0 ref for polarity, as the wave below and above are opposite each other.
Like you said, goes in one way, stops, goes the other.
The one phase you have taken the time to so delicatly describe (kudos!) would at any 1/60th of a second be either above or below the time line.
Any one wave would exist until the magnet coil turned, the polarity changed, and it appeared again on the opposite side of the time line.
I did not think that an equal and opposite wave could exist simutaineously on the time line, i thought it must wait for the coil(s) to turn.....
I must apologize for the 'wave ' thing here, but it's rather imbedded in the ol' gray matter


Steve, forum knuckle dragger....

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