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Litz wire is multistranded wire where each strand is insulated from the others along the wire's length, but they are connected together on each end. This is useful primarily to reduce the skin effect, so that more high frequency current can be carried on less copper, saving cost, weight, and volume. Inductive cooking surfaces often use Litz wire.

Does Litz wire require different equations for inductance than regular stranded or solid wire?

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    \$\begingroup\$ In a word ... no. \$\endgroup\$ – Dave Tweed Feb 27 '14 at 19:19
  • \$\begingroup\$ No, the equations are the same. With the lower losses of Litz you might be able to get more turns. \$\endgroup\$ – Spehro Pefhany Feb 27 '14 at 19:33
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I would think there would be a slight difference but very little and that would depend a lot on the operating frequency. Two quotes gleaned from Google and appear to be reliable sources:

"Litz wire is used to make inductors and transformers, especially for high frequency applications where the skin effect is more pronounced and proximity effect can be an even more severe problem. Litz wire is one kind of stranded wire, but, in this case, the reason for its use is not the usual one of avoiding complete wire breakage due to material fatigue."

"Litz wire conductors are beneficial for reducing A.C. losses in high frequency winding"

So this is just to make a point that Litz wire is used to improve effeciency, this would be especially so in SMPS like computer PSU's where the transformers operate at high frequencies. It's not used for inductance reasons as far as I am aware and probably makes little difference.

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Litz wire inductance should be the same for un-stranded and stranded-but-uninsulated wire.

It should also be noted that Litz wire reduces current proximity effect. But.......

EDIT

I sat down and thought about this a bit more and it occurred to me that skin effect (the phenomenon that increases a wire's resistive losses with frequency) must also slightly change the inductance and this effect could be different for Litz wire compared to other types of wire so I'm posting this picture I got from this site here and maybe someone can give a more definitive answer than mine: -

enter image description here

EDIT 2

For a given total conductor cross sectional area, the internal eddy currents in solid wire that drive current to the "skin" must be smaller in Litz wire. Those internal eddy currents don't represent loss but, represent a reduction in inductance therefore, I would say, that at those frequencies where Litz wire is more effective than solid wire, the inductance of Litz wire should be slightly higher.

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