Anna Conda
Banned
Anywhere you have a Tx with low leakage, by default it has high coupling and reduced proximity effect in the wires, this is why single layer wound Tx's with sandwiched layers of pri-sec-pri-sec etc work so much better than other constructons...
Having the same winding with more than one layer rachets up the proximity effects, whether ETD49 or planar...
True litzendraht wire takes each strand from the middle to the outside (and back again) in a defined length (e.g. 5cm) which guarantees uniform current density, crappy imitation litz does not do this and runs hotter. The graph above by andre shows hardly any variation in current density for the 0.1mm wire on its own (look at the scales), for typical engineering work you would live with 10% to 50% current density reduction at the centre of the wire.
The theory predicts that for really oversized wires (and/or very high freq) you get reverse currents in the wire that are compensated by other currents at the periphery, giving really large losses, and this is proven by experiment, notice in high power RF the wires are copper tubes...this is the reason...
Having the same winding with more than one layer rachets up the proximity effects, whether ETD49 or planar...
True litzendraht wire takes each strand from the middle to the outside (and back again) in a defined length (e.g. 5cm) which guarantees uniform current density, crappy imitation litz does not do this and runs hotter. The graph above by andre shows hardly any variation in current density for the 0.1mm wire on its own (look at the scales), for typical engineering work you would live with 10% to 50% current density reduction at the centre of the wire.
The theory predicts that for really oversized wires (and/or very high freq) you get reverse currents in the wire that are compensated by other currents at the periphery, giving really large losses, and this is proven by experiment, notice in high power RF the wires are copper tubes...this is the reason...