Sounds good..
No I did not use any scripting tools although FEMM does come with LUA.[?] I'm a general all around knuckle dragging novice who bends what might be available to produce possibly incorrect results. I've checked with the Author and the license, whilst 'unusual', does not apply to results from the software.
The basic, approximate, core/winding model was produced in QCAD to get a DXF file which FEMM will import. Then I added the various block labels within FEMM. The concepts behind the program are so far above my head as to be almost inconceivable.
Page 41) of the manual under
2.3.11 Block Integrals describes how to determine self and mutual inductances based on what is effectively, to my mind, stored energy. There does not appear to be a 'reasonable' way of extracting 'leakage inductance' or rather one that I would understand. As a result I 'cobbled' one together...
Overall model was,
One winding section..
There are four 'circuits' involved. This one shows C1/C4. The other side uses C2/C3 which are the same magnitude currents but reversed. Those currents are set to 'cancel' according to turns ratios. Ideally you would expect the result would be that no overall energy is stored. The assumption is that any that is measured would be attributable to leakage inductance and therefore indicative of its value..
Setting Circuit 1/2 to 28/-28 Amps and Circuit 3/4 to -1/1 Amps and running the analysis at the expected switching frequency of 64KHz gives.. Pretty Pictures!!!
Flux Density B,
Field Intensity H,
Energy is B X H so you can see the leakage component is sitting between the windings. Red X Red is Exceptionally RED. It is one of the reasons why you sandwich Primary/Secondary or Secondary/Primary.
Doing the block integrals my assumption is that the indicated inductance, based on such energy, is indicative of the leakage inductance associated with that winding..
For the secondary,
Working out the magnitude as SQRT[Re^2 + Im^2] and dividing by 1A^2 gives 823nH.
It is a value I might be wary of and as a result question my methodology. FEMM does give reasonable answers when checking other things and I would not doubt those results using the described methods. In this case since it is me 'guessing' then the results may not be guaranteed.
For the primary,
Working out the magnitude as SQRT[Re^2 + Im^2] and dividing by 28A^2 gives 11.44nH.
FEMM also takes care of skin and proximity effect although once again I might be using it incorrectly. Putting the values so far back into LTSpice and running a transient analysis lets you do an FFT to determine relative contributions.
Slight danger is how you might, or I would expect to, translate from LTSpice results to FEMM. There must be a DC component for which I have used the 'average' value,
Then for the AC components LTSpice plots RMS whilst FEMM uses peak so they need to be converted,
and put back into FEMM for each frequency of interest then summed to get the overall result. I have just used values for the primary current and assumed the secondary will be proportionate according to the turns ratio.
The block integral is for 'Total Losses'.
Regarding core loss I have just calculated a Bpeak excursion and used the manufacturers data sheet graphs to get an approximate value for that based on Bpeak and the switching frequency. I don't doubt FEMM could give something more accurate but then it depends on the driver and the methodology.
Have fun, take care.
Genome.