HF transformer losses less with reduced magnetization path

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Hi all,

I have two Metglas C cores forming a high frequency transformer O
core. I found that wrapping primary and secondary windings on the
same bobbin as opposed to wrapping them on separate bobbins on
opposite sides of the core has a profound improvement in transformer
core efficiencies. I am aware that doing so would reduce the
leakage inductance significantly, but that shouldn't affect core
hysteresis efficiencies (up to 10% more efficient) I would think
since
I'm recycling flyback currents anyway. Perhaps covering half the
transformer with windings instead of most of it reduces core eddy
currents, but as these cores are laminated composites I believe the
eddy currents are low as it is. Either way, with a reduced
magnetization path the coupling is better. I just don't quite
understand what core loss mechanism is subdued in doing so. Any
ideas?


Thank you,


JT