[Lowfer] Litz Wire Resistivity

[Lyle Koehler]

The New England Wire and Cable Company has apparently changed its name to
New England Electric Wire. Their Litz wire information page is at
http://www.neewc.com/litz/litz.htm

The formulas they give on the succeeding pages may be correct, but I think
they screwed up their arithmetic someplace in the following example, which
was for 450 strands of #40 wire at 100 kHz:

"The A.C. resistance is, therefore, 1.0344 x 2.70 or 2.79 ohms/1000 ft.

The value of Litz can easily be seen if the above example is compared with a
solid round wire with equivalent cross sectional area, 65.8 mils in
diameter. Using the same operating parameters, the D.C. resistance is 2.395
ohms/1000 ft. However, the A.C./D.C. ratio increases to approximately 21.4
making the A.C. resistance 51.3 ohms/1000 ft."

This says that Litz wire has 18 times less resistance than a solid wire of
the same cross section. I seem to recall that when I went through the
arithmetic, the actual advantage was somewhere around 2 or 3 to 1. And be
prepared for sticker shock if you can't find Litz wire on the surplus market
and have to order a batch of it!

Lyle, K0LR