Formula for delta star in capacitors

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SUMMARY

The discussion focuses on the delta-star conversion formula for capacitors, specifically how to find equivalent capacitance using this method. Participants highlight the importance of treating capacitors as impedances, using the formula ##\displaystyle \frac{1}{j\omega C}## to facilitate the conversion. The quick approach involves applying the delta-star transformation to the impedances and then converting back to capacitance, while the slower method relies on first principles. Key insights include the cancellation of frequency (ω) during calculations to simplify the process.

PREREQUISITES
  • Understanding of AC impedance and its relation to capacitors
  • Familiarity with delta-star conversion techniques
  • Basic algebra for manipulating equations
  • Knowledge of capacitor behavior in electrical circuits
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  • Study the application of delta-star transformations in circuit analysis
  • Learn about AC impedance calculations for capacitors
  • Explore advanced algebra techniques for electrical engineering problems
  • Investigate practical examples of equivalent capacitance in complex circuits
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Electrical engineering students, circuit designers, and professionals working with capacitive networks who need to understand delta-star conversions for capacitors.

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Homework Statement



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


Homework Equations



Delta star conversion formula of capacitors

The Attempt at a Solution



Using the formula of resistors but not coming.What is the formula of delta star in capacitors?
 
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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.
 
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.
 
Curious3141 said:
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.

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=...?
 
Greg Arnald said:
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=...?
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.
 

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