Re: Capacitor Purchase

>>From Esondrmn-at-aol-dot-comWed Jun 19 21:30:48 1996
>Date: Wed, 19 Jun 1996 19:13:58 -0400
>From: Esondrmn-at-aol-dot-com
>To: tesla-at-pupman-dot-com
>Subject: Capacitor Purchase


>I was just about ready to order another capacitor from Condenser Products
>when David Lawrence said I could buy his.  He was in on the last group buy.
> It is .025 mfd rated at 20 kv, which is what I was going to order anyway.
> David has been too busy to finish his system and graciously let me have his

>Now, all I need to do is clean up the oil mess and hook up the new capacitor.
> I think I will lower it down in the coil mounting cabinet.  The cap that
>blew up was mounted only about 18 or 20" below the primary - maybe this had
>something to do with its demise??  I had raised it in order to shorten all
>the primary interconnects.

>Has anyone else ever ran their coil with the cap mounted this close or closer
>to the under side of the primary?  At 5 to 9 kva?

>Ed Sonderman

Hi Ed,

I just finished a test run tonite with the three 0.04 mfd-at-100kV 
Maxwells  I picked up at Dayton in parallel on my MTC unit. I did not achieve
the record point to point measured discharge of 12 feet at 7000 watts which I 
got two weeks ago from this system with the somewhat  more Tesla 
efficient total of 0.10 mfd  capacitors (polypropelene) I have from Condenser
Products, but I still did not do too badly today at 10.5  feet to a grounded target.
(same input power).  Conditions were vastly different today with pre-thunder
storm humidity hanging thick  in the air.
I had to decouple (raise) my secondary to stop primary to lower secondary
explosive flashovers which had not occurred in the drier air 
pre-tests in the lab earlier at the same coupling (around K= 0.18).  
I dropped below K=0.18, but did not measure the new employed value.  
I was hurrying the outdoor test afraid of rain on its way. 
This of course lowered my throughput power to the secondary and 
certainly is somewhat responsible for reduced output spark length. 
I am running a flat spiral of  1 inch wide  by 100 thousandths thick copper strap
primary.  The primary is only about 7 inches above the capacitors.  I attribute
NO problems to the proximity of these plastic cased caps to the magnetic 
field of the primary at this distance, but I have them at the outside 
of the diameter where the field is weaker.  As a matter of fact, they 
are IN A STRONG FIELD because the routing of the wide copper 
interconnect strap which puts this cap bank in series with the rotary 
break and the primary coil forms a large single turn around the 

I have heard questions from others as well, wishing to know how
far away is safe to put other system components from the tremendous field of
the primary.  The answer will be different in every case because of differing coil 
geometries and field flux shapes and densities.  You can map these fields by 
exciting your complete system, primary circuit gap shorted and supply 
circuit disconnected, with a signal generator as source.  Use a hand held pickup
coil on your O-scope.  I figure that once the field is down 80% or beyond,  you
have found a really safe area to locate other components and still retain some

Ed, I don't think proximity to the primary was your cause of 
capacitor failure given the generous distance dimension you quote to 
your capacitor location.

Aren't these darn things fun?

Happy Coiling!, rwstephens