Transformer Coupling Coefficient vs Leakage

Feb 21, 2011 2 Replies

I have a spice simulation that uses this transformer:



Turns Ration Np/Ns = 1: 278



Primary inductance = 40uH



Secondary Inductance = 3.09H



Coupling Coefficient K = 0.8 (it's a cylindrical rod core transformer)



I would like to change K to 1.0 and add external leakages so that the simulation results are the same.



This is what I tried:



Set K=1.0 Add a primary leakage of (1-K^2) * 40uH = 14.4uH Add a secondary leakage of (1-K^2) * 3.09mH = 1.11H



The results were close but not the same. So what leakage values should I use?



Jason.


hint: so now your total primary inductance is 54.4 uH and you total sec is

4.1uH. Is that right?

Mark

OK...

With the equivalent circuit model I think you're using here, I believe that you want:

1) A series inductor for primary leakage of 14.4uH as you state, but *no* secondary series inductor. (Although if you feel like it you can of transform some or all of the leakage inductance to the secondary.) 2) Change your turns ratio to 1:1/(k*sqrt(Lp/Ls))=1:347 3) Change the primary's inductance to k^2*40uH=32uH.

How's that work?

---Joel

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