Re: Test of 6" coil

To: tesla-at-poodle.pupman-dot-com
Subject: Re: Test of 6" coil
From: Tesla List <tesla-at-stic-dot-net>
Date: Fri, 30 May 1997 09:47:35 -0500
Approved: tesla-at-stic-dot-net
Subject:      Re: Test of 6" coil
       Date:  Fri, 30 May 1997 06:29:13 -0700
       From:  Bert Hickman <bert.hickman-at-aquila-dot-com>
Organization: Stoneridge Engineering
         To:  Tesla List <tesla-at-pupman-dot-com>
 References:  1


Tesla List wrote:
> 
> Subject:  Test of 6" coil
>   Date:  Wed, 28 May 1997 13:40:39 -0400 (EDT)
>   From: Esondrmn-at-aol-dot-com
>     To: tesla-at-pupman-dot-com
> 
<SNIP>
>  As I started
> to bring the voltage up on the variac, the welder started growling, the
> spark
> gaps started to fire but weak and erratic - just like last time I tried
> to
> run it.  No spark breakout from the toroid.  I was in the process of
> closing
> the switches one at a time on the resistive element bank to see if this
> would
> make any difference when everything stopped.  The 30A fuse on the
> powerstat
> variac was blown.  I traced this problem to a short in the secondary.  I
> further traced this problem to a shorted capacitor.  My trusty Simpson
> VOM
> measures about 10 ohms across the capacitor.  This is a Condenser
> Products
> cap .025 mfd rated at 20,000 volts AC.  This cap came from the second (I
> think) group purchase.
> 
> At least this cap did not blow up like the last one.  I don't understand
> how
> I can possibly be doing anything to destroy these caps.  This is the
> second
> Condenser Products cap that I have lost.  Anybody have any ideas here?
> Am I
> just having a bad run with C.P. caps???  I will call them today and see
> if I
> can send this unit back.
> 
> Looking at my notes from last July, I did get this capacitor to run good
> in
> the system one time.  I set a new distance record of 80" discharges at
> that
> time.  It ran for maybe 15 minutes and then the primary started acting
> up -
> just like it was this time before the cap finally shorted.  I am
> guessing
> that maybe I don't really have any primary set up or design problem and
> the
> only problem has been bad caps.
> 
> I know there has been a lot of debate about this, but who should I go to
> next
> time?  Plastic Capacitors?  Has anyone on this list had one of their
> caps
> fail?
> 
> Ed Sonderman

Ed,

Well, at least you now know where the "flakiness" in the system was
coming from. :^( 

My suspicion is that the caps you got had some type of latent defect
which caused them to short out. The most probable cause is entrapped air
deep inside the capacitor roll(s). After a period of extended running,
the localized heating and chemical degradation of the dielectric/oil
causes a failure. 

It's certainly worth discussing with CP to see if they'll do anything
for you. You've got absolutely nothing to lose at this point! If they
won't, I'd check out Plastic Caps. The construction technique of the
latter is, in my opinion, superior to that of CP. 

Good Luck!

-- Bert --