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Negative sequence currents in an alternator

  1. May 14, 2016 #1

    cnh1995

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    We recently performed one experiment regarding measurement of negative sequence impedance of an alternator(unloaded) in our lab session. The alternator was star connected and we shorted Y and B phases together, leaving R phase open(an L-L fault). How does this arrangement generate negative sequence currents? How is the direction of rotation of magnetic field reversed? Please help. Many thanks in advance!
     
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  3. May 14, 2016 #2

    anorlunda

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    https://en.m.wikipedia.org/wiki/Symmetrical_components

     
  4. May 14, 2016 #3

    cnh1995

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    We measured the open circuit voltage VRY and short circuit current IYB. The ratio VRY/IYB is the negative sequence impedance. How?
     
  5. May 15, 2016 #4

    anorlunda

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    Well, the very definition of impedance is the ratio of voltage to current. The only question is which impedance it is it?

    I suggest that you study symmetrical components enough to solve the homework problem of making an equivalent circuit for a L-L fault. Once you have that, it should be obvious which impedance you are measuring.
     
  6. May 17, 2016 #5
    You should be able to plug and chug, but I'm not able to use a program to give me a quick and dirty answer, and I don't have time to do the calculation by hand.

    See if this can shed any light onto your problem...
    https://cdn.selinc.com//assets/Lite...etrical-Pt1_AR_20130422.pdf?v=20150812-081134
     
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