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Parallel Impedance to Series?

  1. Nov 6, 2014 #1

    If I have two brances, branch 1 and branch 2 which are in parallel and each branch has a resistance and inductance, to calculate the equivalent series resistance and inductance, can I calculate the resistance and inductance separately e.g.

    Req = R1*R2/R1+R2 (and same for X),

    or do I have to do it combined E.g.

    Zeq = (R1+jX1)*(R2+jX2)/(R1+jX1)+(R2+jX2), and then convert to polar etc and back to rectangular to find the equivalent R and jX values? The two methods give me different answers?

    Sorry, forgot to add, the values of R and X are in PER UNIT
  2. jcsd
  3. Nov 6, 2014 #2


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    2017 Award

    Staff: Mentor

    And the second one is correct. That should answer if the first one works.
    Note that there are brackets missing.
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