CataM
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Here's the diagram from my book (K. Simonyi, Theoretische Elektrotechnik)
View attachment 146698
The x-axis unit r0 is r/δ, wire radius divided by skin depth. R/R0 is Rac/Rdc ratio. Inner inductance is also plotted.
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Yes, I figured out FvM was referring to a single wire afterwards.
I was initially posting about "transformer windings" where it is assumed windings are wound in layers and hence only 1D H field is possible, hence Dowell expression is somehow accurate.
The strange thing is Easy Peasy's claim of 15% rise of their Rac with respect to Rdc with the claimed wire size. Obviously he is hiding some details.
See post #18, it's wire inner inductance and inductance increase due to skin effect, not relevant for the present discussion in the first order, although playing a role for current sharing of paralleled windings. It's simply printed in the book along with Rac.per the above, #22, what are the y axes for the 2 other plots?
Also, just for completeness, if you have a resonant converter with basically sinusoidal current, then harmonics don't come into play, for square wave currents the harmonics add very little, as the first is I/3, 2nd is I/5 and so on, the I^2 R product of these and vector summation amounts to <5% extra losses ...
Yes, I figured out FvM was referring to a single wire afterwards.
I was initially posting about "transformer windings" where it is assumed windings are wound in layers and hence only 1D H field is possible, hence Dowell expression is somehow accurate.
That assumption is incorrect (almost is not correct, it is very far in fact for the example we are discussing) for the case of layers in transformers. Dowell expression must be used and is widely accepted in industry (also by the document you provided in one of your earlier posts).The assumption is that you get almost similar current distribution in a single wire and interleaved single layers because proximity effect cancels out. There are some deviations from the ideal picture, top and bottom layer, also borders. 15% versus 8 % of the no proximity case seems realistic.
Yes, I do agree.But whether Rac in this configuration can come near to single wire or not, you surely agree that it can't be smaller, which was the question of the recent debate.
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