Lr Value of Integrated Transformer in LLC Converter

[txbob]

Hi,
Can I measure the Lr Value of an integrated transformer by shorting secondary and measuring the primary inductance or Is the measurement techniques for Lr is same as measuring the leakage inductance of the typical transformer?
Help is appreciated

Bob

 

[FvM]

I don't know what you mean specifically with Lr. You can identify all parameters of LLC transformer by measuring primary and secondary inductance with other side open and shorted. Choose an appropriate equivalent circuit, e.g. T-circuit and determine the values by parameter comparision.

 

[cupoftea]

Also, Page 4 tells you how to measure your LLC txfmr parameters...

https://www.onsemi.com/pub/collateral/an-4151.pdf

 

[txbob]

@cupoftea ...Thank you very much. Thank you for the link .It helped to clear the doubt

 

[FvM]

Allocating the total leakage inductance to the primary side can be useful for some applications but changes the apparent winding ratio of your equivalent circuit.

 

[Easy peasy]

In that On-semi article the leakage all referred to the primary is assumed to be Lr, this is a fairly close approximation, as is assuming you can measure Lp ( Lprimary ) with the sec open - actually this measurement is Lpri ( actually Lmag ) + L'leak, where L'leak is that leakage associated with the pri that does not couple to the sec.

But these approximations get you near the ball park. [ just for completeness the measurement when sec is shorted is L'leak + L"leak, where L"leak is the sec leakage ( that which does not couple to the pri ) reflected to the pri side, there is also the parallel ( shunt ) path of Lmag, to some extent L'leak and Lmag cancel each other to get closer to L'leak ( ~ = Lr ) ].

 

[txbob]

I don't know what you mean specifically with Lr. You can identify all parameters of LLC transformer by measuring primary and secondary inductance with other side open and shorted. Choose an appropriate equivalent circuit, e.g. T-circuit and determine the values by parameter comparision.

Thanks for your reply.I am attaching the detailes for Lr

Allocating the total leakage inductance to the primary side can be useful for some applications but changes the apparent winding ratio of your equivalent circuit.

Wow...Thank you so much. I missed this point for my simulation

--- Updated Jun 29, 2021 ---

Allocating the total leakage inductance to the primary side can be useful for some applications but changes the apparent winding ratio of your equivalent circuit.

@FvM .. measured Lpri is 900uH and measured Llk (Lr) is 326uH, Now Lr is separated in simulation model. That means 36% reduction in inductance corresponding to 6% reduction in Turns ratio for simulation.. Does this make sense?