Re: Secondary runners

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Tesla729-at-cs-dot-com>

In a message dated 9/24/01 6:53:09 PM Central Daylight Time, tesla-at-pupman-dot-com
writes: 


>
> Hi List, 
>
>      What besides cupping can cause arcs to race down my secondary. It is 
> happening with one of my smaller coils (1.75 inch by 10 inch winding length).
>
> The coil form is acrylic tube, and the bottom turn of the secondary is even 
> with the bottom turn of primary. The primary is a 30 degree cone type
> primary, 
> with 9 total turns at .5 inches apart. Torrid is 3 inch by 8 inches OD, and
> my 
> capacitors are TDK UHV series Strontium Titanate pulse rated capacitors. The 
> cap bank is right at .01uF, and that is perfect for my 9/30. All I can seem
> to 
> get out of the coil is 12 inch arcs, and with those I get runners. Perhaps it
>
> is because of my single static non-quenched gap that I am using until I have 
> time to make a better one. What do you think? 
>



Rick, 

Your secondary "runners" are what most of us coilers 
refer to as "racing sparks". There are a couple of pos- 
sible causes for this phenomenon, namely over-coup- 
ling of the primary/ secondary coils and / or improper 
tuning. Judging by your description of your coil and 
also due to the fact that you have built more than one 
coil, I would say that your coil is over-coupled. Try 
raising your secondary coil a little higher, say in 1/2" 
increments above plane of the base of your primary coil 
until the racing sparks cease. Often, the secondary's 
bottommost winding has to be elevated slightly above 
the innermost turn of the primary to achieve proper 
coupling. Critical coupling is the point where maxi- 
mum coupling is achieved w/out the racing sparks. 
Hope this helps. 

Sparking in Memphis, 
David Rieben