Re: Primary AC resistance measurements, Part 3

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Gary,

On 15 Aug 2002, at 11:25, Tesla list wrote:

> Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<Gary.Lau-at-hp-dot-com>
> 
> For those following the primary inductor AC resistance measurements that I
> began 1-2 months ago, I have a new installment on my web site.  See
> http://www.laushaus-dot-com/tesla/primary_resistance.htm
> 
> I discovered that my marginally-performing Litz wire was in fact comprised
> of #30 strands, not #38 as I was led to believe.  Since higher frequencies
> require finer stranding, I think this accounts for what was measured.
> 
> I re-measured the #10 stranded coil and found that the test leads I had
> used for just that coil added significantly to the resistance.  The new
> data still shows that stranded wire is a poor choice.
> 
> Part 2 data showed that a two-layer copper tubing primary had a much higher
> resistance than a single-layer version,  But it wasn't clear if this was an
> artifact of the two-layer construction, or the fact that there were four
> unused turns on each of the two layers.   I built a #14 solid wire
> two-layer coil, but with no unused turns, to compare against the 1-layer
> #14 coil.  The results of this were not at all definitive.  For the 1/4"
> tubing, the 1-layer coil had the lower resistance (over all frequencies),
> while with the #14, the 2-layer coil had the lower resistance (until
> somewhere above 400 KHz). Not sure what to conclude...
> 
> Regards, Gary Lau
> MA, USA

I think it's reasonable to say that if the 2-layer coil works well in 
practice then for reasons discounting its higher ESR it is a useful 
choice. I would like to be in a position to do a direct comparison in 
a running coil with both types and the system set to the same k but 
unfortunately I have nowhere to run coils at the moment. I expect 
that the gap would probably swamp differences between the two but it 
would be good to see a running comparison.

Regards,
malcolm