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Re: Litz Wire

Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>

On 8 Mar 2005, at 7:58, Tesla list wrote:

> Original poster: "Mike Knowlton" <amdx@xxxxxxxxxxxxxxxx>
>  > Hi All,
>  >    I have about 1100ft of 12/36 litz wire, my >understanding is
>  this wire
> is good to about 50 khz. If I >wind a secondary with this and it rings
> at say 200khz, is >this litz any better than a #30 or #28.
>    > Mike
>  >Hi Mike
>  > I built a secondary using Litz wire once (in my early coil
>  >building
> days). No significant difference in performance >or Q was noted over
> using a suitable gauge of solid Cu. >Litz is usually specified as
> being most useful in the MW >broadcast band where the higher frequency
>  > (smaller) coils operate but by the time you approach >500kHz to
>  1MHz > you find that more inductance is better than more Q, at >least
>  for
> disruptive discharge coils.
>  >
>  > Malcolm
>   Hi Malcolm,
>    Do recall what size litz you used, it makes a difference,
> the ideal wire size is #42 from 200 to about 350khz and #44 from
> 350khz to 850khz. See
>     http://www.litz-wire.com/technical.html

I took a micrometer home and measured the wire. #xx has no meaning to
me. We exclusively use metric units here. The wire on that particular
coil was 7-stranded Litz, each strand measuring 0.09mm Cu (enamel
thickness discounted). The resonant frequency of the bare coil from
memory was somewhere around 350kHz. With a 9" sphere topload it
dropped into the 200's somewhere.

>  >>No significant difference in performance or Q was >>noted over
>  using a
> suitable gauge of solid Cu.
> Someone will have to calculate this, I have seen litz make a large
> difference in the Q of an inductor. I hope someone beats me to the
> calculation, but for now let's agree on a common wire size for
> comparison purposes.  How about # 22??   and 300Khz for the resonant
> freq.
>   I'm open to change these numbers if some other coilers
> have better info.
>                                   Mike

The point I was trying to make is that any improvement in performance
you'll make for a sparkgap coil is as good as zero. Typical TC
resonators already have Q's ranging from 150 to 300+ and most system
losses occur in the primary gap (and primary capacitors with lossy

     BTW I did conduct an experiment once which showed Litz with a
comparable Cu x-sectional area did much better than stranded wire and
braid but only a small advantage over solid copper. Each type of
conductor was cut to the same length (about 5m) and inserted between
a resonator base and a good ground. The differences in Q were easily
measured and in some cases starkly contrasting.