1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Formula for delta star in capacitors

  1. May 15, 2014 #1
    1. The problem statement, all variables and given/known data

    How to find out the equivalent capacitance using delta star conversion?


    2. Relevant equations

    Delta star conversion formula of capacitors

    3. The attempt at a solution

    Using the formula of resistors but not coming.What is the formula of delta star in capacitors?
     
  2. jcsd
  3. May 15, 2014 #2

    Curious3141

    User Avatar
    Homework Helper

    The slow way to do it is from first principles.

    The quick way is to use the AC impedance of a capacitor, which is ##\displaystyle \frac{1}{j\omega C}##, which can be treated like a resistance, then apply the delta-star conversion formula to it and see what you end up with. Remember to convert the final impedance you get back to a capacitance by reversing the formula.
     
  4. May 15, 2014 #3

    UltrafastPED

    User Avatar
    Science Advisor
    Gold Member

    The delta-star transformations work for more than simple resistance - they work for any impedance.

    So just convert the capacitances to impedances ... and use the formulas for resistors.

    Then convert the impedances back into capacitances.
     
  5. Apr 19, 2017 #4
    Hi Curious3141,
    quick run down.... C1 across b and c, C2 across c and a, C3 across a and b.
    I'm trying to derive the formula for Ca in terms of C1, C2 and C3.
    If these capacitors were resistances the formula would be Ra=(R2R3/R1+R2+R3) (I think ?)
    there for if capacitors.. 1/ωCa=(1/ωC2*1/ωC3)/(1/ωC1+1/ωC2+1/ωC3). (??)
    How do I convert this back to capacitance so I just have Ca=.......???
     
  6. Apr 19, 2017 #5

    gneill

    User Avatar

    Staff: Mentor

    Looks like it's just a bit of algebra. Logically, you know that ω should ultimately play no role in the capacitance values you obtain, so it should cancel out along the way. Might as well just eliminate it from the start (or choose a convenient working frequency such as ω = 1). That may make things less cluttered looking.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Formula for delta star in capacitors
Loading...