Re: Optimal toroid elevation

To: tesla-at-pupman-dot-com
Subject: Re: Optimal toroid elevation
From: "Malcolm Watts" <malcolm.watts-at-wnp.ac.nz> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
Date: Sun, 28 May 2000 20:28:40 -0600
Approved: twftesla-at-uswest-dot-net
Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

Hi Terry,
               This is a beauty you've raised here:

On 26 May 00, at 13:32, Tesla List wrote:

> Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
> 
> Hi Bart, Jeff, Marco,
> 
> 	There is a subtle detail here you need to be aware of.  
> 
> 	As long as the torroid is raised a few inches above the top of the
> secondary, the program should work fine.  However, if you are setting the
> toroid directly on top of the secondary, it is probably changing the
> secondary coil's inductance.  Try to remeasure the secondary's inductance
> with the toroid in place as in Test #1 below.  It will probably be about
> 10% lower than without the torroid in place.  I did a quick test and my big
> coil went from 75.4mH to 68.9mH  (about an 8.6% drop in inductance)  The
> torroid is messing with the secondary's inductance since it is so close.
> In a normal coil, the little distance between the top of the secondary and
> the toroid provides enough isolation.  However with them in almost direct
> contact, the secondary inductance will change.  Since E-tesla does not
> account for this inductance variation, it will not give the best answer.
> This may also be a problem if you have a corona ring on the top of the
> secondary but I "think" that ring should have a split in it which should
> fix the problem??

I have tried exactly this a few years ago and found that slitting the 
topload had little effect on the resonant frequency - far less than 8 
%.  I think Greg Leyh tried the same thing on his 40kW coil with 
much the same result. I will include this in the next series of msmts I 
am planning.

Regards,
malcolm

<snip>