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Thread: May I ask a question about the single vs two phase stuff

  1. #911
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    Quote Originally Posted by jaggedben View Post
    Three phase doesn't have a time delay either. No matter what the setup, a 'shift' in 'degrees' never actually means a delayed start for 2nd or 3rd phases in the real world. It's all just mathematical representation that allows us to do some types of engineering as long as real world waveforms resemble ideal sine waves within acceptable tolerances.

    If the 120/240 service was the only kind of electrical service that existed, and if power factor and three-phase power weren't things needing to be analyzed, no one would ever have bothered to make phasor math part of electrical engineering education. I know that's a lot of 'ifs', but the point is, inversion really is all the math you need to analyze this service with resistive loads. It doesn't 'make sense' to use phasor math if a much simpler mathematical operation produces the same result that meets your needs. If you were programming software, for example,I believe you'd need a lot less computing power using inversion. (Not very important with today's devices, but I remember the TI-88.)

    Now, I totally respect the position that says 'well, I'm trained to do phasor math for all these other applications so it's just natural for me to employ it here as well.' But there is nothing ontologically privileged about phasor math. It doesn't represent what the waveforms 'are'. The 'time delay' discussion pretty much proves that.

    Mind you, I think we're on the same page here. I'm just quibbling with how your putting it. I'm 'just sayin'.
    See, you wanna be reasonable here, ain’t gonna work!

    I seriously wanna explore Wayne’s earlier idea of of -1, instead of our more traditional methods of analysis of the secondary-vectors, phaser math, common reference of the neutral for a dual winding secondary, etc, gonna start a new thread in education forum, mathematics and trig only!

    And another thing to talk about the way the secondary loads could impact the primary. Again a single thread on that would make sense. Windings, flux, currents, etc. To do this we need to consider the primary load’s impact on the POCO side also. This where it can really mess me up. I got no problem doing the simple primary and secondary calcs on a tranny, but distribution line calcs-nope, I am out.
    "Electricity is really just organized lightning." George Carlin


    Derek

  2. #912
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    Winnie (and others), the circuits I were describing are tube based audio. Some may feel they aren’t relevant but a transformer doesn’t know that and acts the same regardless. I think it is easier to see the 180 vs -1 point when considering music. There you have no pure sine waves and R,C, and L are always in play.

    Bottom line. Voltage transformation is proportional to turns ratio. Current transformation is inversely proportional to turns ratio. Impedance is proportional to square of turns ratio. And on a center tapped transformer, the impedance from end to end is four times the impedance from center tap to either end. Does not matter what the transformer is being used for.

  3. #913
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    Quote Originally Posted by Russs57 View Post
    Winnie (and others), the circuits I were describing are tube based audio. Some may feel they aren’t relevant but a transformer doesn’t know that and acts the same regardless. I think it is easier to see the 180 vs -1 point when considering music. There you have no pure sine waves and R,C, and L are always in play.
    You know, I may have started this whole kerfuffle three threads back, and what you say is precisely the issue I brought up. There is no amount of phase shift you can apply to a complex waveform where it is indistinguishable from an inversion. I'm an old analog audio guy, myself; although most people even in audio colloquially refer to the signals in a balanced line as being "180 degrees out of phase", that's not what they are.

  4. #914
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    Quote Originally Posted by jumper View Post
    Hmmmm.





    Both are types of common single phase services.

    Math works both set ups. Two signals combined to create a larger one.



    Where did you get this? This is gold to me.
    I'm in over my head...

  5. #915
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    Quote Originally Posted by Russs57 View Post
    Winnie (and others), the circuits I were describing are tube based audio. Some may feel they aren’t relevant but a transformer doesn’t know that and acts the same regardless. I think it is easier to see the 180 vs -1 point when considering music. There you have no pure sine waves and R,C, and L are always in play.
    I, too, am familiar with audio and the center-trapped transformer used as a phase splitter to drive a push-pull output stage by a single-ended intermediate stage. If you think about it, this truly is a matter of signal inversion, and not a timing offset/delay.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
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    Richmond, VA

  6. #916
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    I find the 240 volt diagram quoted a few posts up to be much prettier than the 208 one.....Although the math major in me is a bit more drawn to the complexity of the 208 one. How to decide?
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  7. #917
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    Sir Besoeker,
    would the 208 volt diagram be like the three phase commercial I am learning for bs7671 training? It looks pretty. But the 240 diagram is what I was taught in 80s... maybe that is why I am having some of the problems visualizing the phase numbers here..lol

  8. #918
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    Quote Originally Posted by jumper View Post
    Hmmmm.





    Both are types of common single phase services.

    Math works both set ups. Two signals combined to create a larger one.
    The 120, the 240, the 208 Volts are RMS values, not peak as shown on the waveforms in the diagrams.
    Si hoc legere scis nimium eruditionis habes.

  9. #919
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    Larry and ggunn, you would think that would put the whole 180 verus -1 one thing to rest. After all, how can that "phase splitter" transformer operate any differently than the transformer supplying 120/240 power to our homes in USA? It is inversion. Doesn't matter if math says it is the same under ideal conditions. Yet some stick to the 180 notion. Doesn't help that audio guys say "180 out of phase". Clearly they know the difference when they are wrapping feedback around things, using compensation networks, and worrying about poles and zeros.

    Now someone made a comment about there not actually being any "time shift" with three phase. I'm picturing a rotating generator shaft and having a little problem with that comment. Might be a chance for me to learn something more out of this thread.

  10. #920
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    But, which one for all those phase questions as part of the tests here? I think the bottom one is what I use but.. not sure..lol..

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