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Dragan,

A practical example that some may find interesting:

Thanks for that! It's interesting to compare his results to mine.

As I understand that video, he measured the impedance of his CMC at small
signal level, and then used software to calculate the losses at a high
applied voltage, assuming that the behavior of the ferrite is completely
linear with power changes. This isn't entirely correct, so there is a
source of some error, but at 5mT flux density that error might still be
small.

A few months ago I did a series of loss measurements at high drive levels
on various ferrite types. I applied RF voltage from a transmitter, in
parallel with a dummy load, just like him, but I thermally insulated the
cores under test, measured the heat rise over a certain time, and
calculated the power loss from this. My method also incurs in some
inaccuracies, for example I only have an estimated value for the heat
capacity of ferrite. That's why it's interesting for me to compare my data
to his.

He applied 276V to 11 turns on an FT-240-31, at 7MHz. This results in
about 5mT flux density. He measures in gauss, calculating 50.7 gauss,
meaning 5.07mT. Good agreement there.

He calculated 18W loss for the core, under those conditions. That's a
volumetric loss of 735mW/cm?.

I don't have an FT-240-31 to test, so I tested two sizes of 31-material
beads. My results differ slightly for the two sizes, which may be due to
measurement error, or to material differences between batches. On my
FB-31-6873 I got a volumetric loss of 500mW/cm? for that flux density and
frequency, while for my FB-31-1020 I got 590mW.

At least my and his values are reasonably close. I wouldn't expect much
better agreement, given that both his and my tests aren't entirely up to
laboratory standards.

My measurements are here: