Auto-Transformer Formula help Please..

Discussion in 'Homework Help' started by stinky111, Dec 4, 2011.

  1. stinky111

    Thread Starter Member

    Apr 7, 2011
    39
    1
    Hi All,

    Im studying for a final & am having problems finding the formulas in my notes to solve the question below..

    An auto-transformer is connected to a 230V a.c supply. the secondary voltage is 50V a.c and the load current is 8A. How much current flows to the common part of the winding??

    Appriciate the formula to find the current flowing to common part of winding please guys?? (Final a week away & I have no more lectures beforehand)
    Thx
     
  2. jimkeith

    Active Member

    Oct 26, 2011
    539
    99
    Iout = Iin + Icom

    Icom = Iout - Iin

    Iin = Iout /Eratio

    Icom = Iout - (Iout /Eratio)

    Try this and see if it works
     
  3. EL7819

    New Member

    Apr 15, 2011
    20
    0
    Np/Ns=Vp/Vs=Is/Ip
     
  4. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    This is partly true for the auto-transformer - to the degree that it relates the input primary terminal current to the secondary terminal current but it doesn't tell you what the common current is in the 'shared' part of the winding. Jimkeith's method is correct.
     
    stinky111 likes this.
  5. stinky111

    Thread Starter Member

    Apr 7, 2011
    39
    1
    Thanks JimKeith,
    so am i correct in saying:

    Ratio = vp/vs= 230/50 = 4.6
    Icom = Iout-(Iout/Eratio)
    = 8a-(8a/4.6)
    = 6.26A??
    Thx..
     
  6. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    Correct.:)
     
  7. stinky111

    Thread Starter Member

    Apr 7, 2011
    39
    1
    Thx heaps...
     
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