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skin effect

I have a planar transformer primary winding that has 0.2mm x 10mm cross-section (two windings in parallel, actually, top and bottom of the PCB; ). It is running at ~450kHz (main harmonic skin depth is ~0.1mm). The thickness of the winding should be well utilized (~50% duty cycle). How about the width? How is current distributed across planar transformer winding (width>>skin_depth)?

Little bit of explanation is probably needed. The previous version of the same winding was thicker (~1mm) and had narrow slot cut in the middle (lengthwise) to make the winding look more Litz-like. I respun the board to try differentt MOSFETs and changed the winding size (made it thin) so it may be laser-cut (as opposed to machined). The efficiency went down by 5% or so. Oooops! New winding DC resistance is 4mOhm (AC should be higher, but by how much??) - too thin, oops again. I stacked them up (three in parallel)

- the efficiency did not change appreciably.

Reply to
Michael
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This should give you a clue as to what direction the winding should be = narrow.

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All the more reason planar transformers are a bad idea... they're planar = in the wrong direction. If you could deposit copper foil edgewise you'd = have something pretty handy.

Tim

--=20 Deep Friar: a very philosophical monk. Website:

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Reply to
Tim Williams

If Litz like cannot be used due to profile height, then parallel single mag wire conductors can be used to acquire skin effect based efficiency gains.

So, like 3 or 4 parallel runs of say #28 will give a better yield than a flat circuit trace or larger, single wire run would. Even cutting up a wide circuit trace into several narrower parallel runs increases high frequency efficiency.

You can also use Litz and smash the winding flat with a jig or fixture before putting it inside the planar assembly. You can also configure your own Litz like winding by twisting the three aforementioned mag wires.

Reply to
Pieyed Piper

Makes one wonder if there is not an as yet un-researched technology using flex circuit mounted "foil" winding laminates.

I have seen a "ribbon" wound transformer core before, but not the winding itself.

Reply to
Pieyed Piper

y handy.

"copper foil edgewise" - cutting slot "lengthwise" is the same "flex circuit mounted "foil" winding laminates is not an option - too flimsy for almost 100A peak currents. I still have to find a way of guesstimating what I really need for copper.

Reply to
Michael

Michael schrieb:

Also think about the proximity-effect..

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Jorgen dj0ud

Reply to
Lund-Nielsen, Jorgen

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