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Three-Phase Delta Network: Not all Voltage Sources are 120V?

  1. Feb 22, 2016 #1
    Using the Delta Netowrk from this image: http://www.belden.com/images/B23_WyevsDelta.jpg

    Between Y-X, there should be 120V.
    Between Y-Z, there should be 120V.
    Between X-Z, there should be 120V.

    But wait!

    If we assign values to make the above statements true...

    Call X = 0V, and Y = 120V, so from Y-X is 120V.
    If Y-Z should be 120V, and Y is already 120V, then Z should be 240V. This is so from Y-Z is 120V.
    If X-Z should be 120V, and Z is 240V, then X should be 360V.

    But that can't be, since we already said X is 0V to make Y-X = 120V. From what I know, if X is held to be 0V and Z is 240V, then from Z-X is 240V!
    If X is made to be 360V, then Y-Z is no longer 120V!

    What am I doing wrong?
  2. jcsd
  3. Feb 22, 2016 #2


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    120V will be the rms value of voltage and not the instantaneous value. Instantaneous values will be different at each instant.
  4. Feb 23, 2016 #3

    jim hardy

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