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Windings loss in an LLC converter?

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Advanced Member level 5
Jun 13, 2021
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Just doing LLC transformer (ETD59 ungapped) for 2kW off 400Vdc to +/-160V….resonance frequency = 100kHz.
Txfmr is Np1_Ns1_Ns2_Np2 = 26_11_11_26
1 primary interleaves the two secondarys
Np1 and Np2 are in parallel. They are the “bread” layers.
Np1 and Np2 are totally 4 strands of 7/0.16mm TEX-ELZ
Ns1 and Ns2 are each 3 strands of 7/0.3mm TEX-ELZ.
We have 3.3W total of windings loss in the primary
We have 1.5W of windings loss in each secondary.

Would you say this is too much windings loss?

are your losses the "DC" losses only ? have you calculated the leakage ?

have you estimated the AC resistive losses @ 100kHz based on current wave shape ?

ETD59 is good for about 6W total losses in still air - all Cu losses + core losses

do you have other cooling ? what is max ambient for full power ? core material ?
Thanks, yes, we have fans. Max ambient is not too clear just yet. Core material N87 ,or 3C96 or 3C90, 3C95.....none of my emails to distys of ferrites have gotten replies yet.
I also need the 1mm gap version of ETD59, as well as ungapped ETD59's.
TEX-ELZ 7/0.16mm appears to be out of stock the world over....ali express none, powermagnetics none, none, ebay none.
Kool mu 77778A7 also looks like being hard to get hold of.

Regarding DC losses am using TEX-ELZ so believe am dealing well with skin effect.
Leakage L of main LLC transformer is around 2.5uH according to FvM help with electromag simulator.

Multiple parallel strands are no equivalent of litz wire and will involve additional proximity losses.

Thanks, the "parallel strands" are themselves Litz wire. They are TEX-ELZ

I dont see that the fact that its TEX-ELZ is going to bring extra proximity loss?

I dont believe its possible to buy proper Litz wire, not as a private individual?
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Regarding proximity loss, and the use of multiple strands of TEX-ELZ, woudl you consider that the proximity loss might be less, due to the insulation between the strands?......

...i mean, please dont get me wrong...i'd prefer something like 50 strands of 0.1mm Litz, but getting hold of that will be all but impossible for a private individual such as myself.
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