Re: Primary AC resistance measurements

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

Original poster: "D.C. Cox by way of Terry Fritz <twftesla-at-qwest-dot-net>" <DR.RESONANCE-at-next-wave-dot-net>


Gary:

If you provide me with your shipping address I will donate the 50 feet of
copper ribbon so you might complete your experiments.

Best regards,

Dr. Resonance




----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Wednesday, June 26, 2002 7:27 AM
Subject: Primary AC resistance measurements


> Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<Gary.Lau-at-hp-dot-com>
>
> Hey All:
>
> The thread several weeks ago about the observed heating of inner primary
> turns got me to wondering about the actual AC resistance of primary coils
> wound with different conductors and what would be the best choice.  I have
> access at work to a very nice instrument that can measure an inductor's AC
> resistance over any range of frequencies.  So I constructed four
> identically dimensioned test primary coils, using these conductors:
> 1. 1/4" copper refrigeration tubing, the standard for Tesla Coil primaries
> 2. #7AWG-equivalent Litz wire, 259 strands of #38AWG enamel-insulated
wire,
> about 1/4" diameter overall
> 3. #10AWG stranded wire, 105 strands of #30 tinned copper
> 4. 1/2" wide by .008" thick copper ribbon
> And I plotted the AC resistance from 40 KHz to 800KHz.
>
> The performance of the Litz wire was marginally better than copper tubing
> to poor, depending upon frequency.  And yes, I'm sure that it truly is
Litz
> wire and that all strands were stripped and tinned together at the ends.
> The AC resistance was only slightly lower than 1/4" tubing below 120KHz,
> and rose to more than 3 times the resistance of tubing at 800KHz.
>
> The performance of the copper ribbon was quite good considering that the
> thickness was only 8 mils, probably less than the skin depth.
>
> And not surprisingly, the performance of the stranded wire was terrible.
>
> The conclusion is that the 1/4" copper tubing that we use is a very good
> choice.
>
> Graphs, data, and photos are on my web site at
> http://www.laushaus-dot-com/tesla/primary_resistance.htm
>
> Regards, Gary Lau
> MA, USA
>
>
>