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Burned Secondary...
From: NTesla[SMTP:ntesla-at-ntesla.csd.sc.edu]
Reply To: ntesla-at-ntesla.csd.sc.edu
Sent: Tuesday, September 23, 1997 9:01 AM
To: tesla-at-pupman-dot-com
Subject: Re: Burned Secondary...
At 08:02 AM 9/11/97 -0500, you wrote:
>
>From: Mark S. Rzeszotarski, Ph.D.[SMTP:msr7-at-po.cwru.edu]
>Sent: Thursday, September 11, 1997 2:59 AM
>To: Tesla List
>Subject: Re: Burned Secondary...
>
>Hello Dan,
> You said in part:
>>I made a couple of changes to my system the other day and promptly had
>>several turns weld together on the bottom 1/3 of the secondary. I cut that
>>part off, retuned, and had the rest of the secondary burn the same way. I
>>don't mind this though...Last time I jumped up a level in coiling, it was
>>because I was burning secondaries (arcing through the inside of the form),
>>but it's not that way this time. Here's the system before the changes:
>>
>>I never saw any inter-turn arcing, but pin-point hot-spots shorted the
>>secondary turns in several places.
> Although you did not provide complete info regarding your primary, I
>ran a couple of computer simulations based on what you probably have:
[snip]
> Assuming the bottom turn of your secondary is even with or above the
>bottom turn of the primary, you are not over-coupled. For a coil of this
>size, I would shoot for a K of 0.18-0.22 range. I am curious, however,
>about your operating frequency. Your primary is tuned to around 125 kHz if
>I made the right assumptions about your geometry. Your secondary is
>self-resonant around 300 kHz, and is probably operating with a resonant
>frequency around 180 kHz, if I am figuring the capacitance of your toroid
>right. If this is the case, you will get some rather nasty standing waves
>on your coil, which could explain your results. You may want to go back and
>check your tuning.
>Regards,
>Mark S. Rzeszotarski, Ph.D.
Excellent! Ok, I had two toroids, stacked one upon the other, each one 24"
x 4" if that makes any difference...I like the standing waves idea because
it's only the bottom 1/3 to 2/3 that's burning. If wire insulation was the
problem, (which it still very well may be), I'd expect the thing to be
burning up all over, *especially* at the top, not the bottom.
In fact...DOH! I may have detuned the coil for a test-fun-thing I like to
do that I won't mention on the list, but it has to do with standing on a
big sheet of lucite barefooted. ;) (no flames please...it won't make any
difference ;)
So now, two questions:
1) Would tapping at 10 turns (the usual point) make that much of a difference?
2) Where can I get the simulation program you're using? <grin>
Thanks,
Dan