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Re: Test of 6" coil

Subject:     Re: Test of 6" coil
      Date:  Thu, 29 May 1997 18:56:08 -0500
      From:  Chuck Curran <ccurran-at-execpc-dot-com>
        To:  Tesla List <tesla-at-pupman-dot-com>
References:  1


Tesla List wrote:
> 
> Subject:  Test of 6" coil
>   Date:   Tue, 27 May 1997 11:51:05 -0400 (EDT)
>   From:   Esondrmn-at-aol-dot-com
>     To:   tesla-at-pupman-dot-com
> 
> I finally got my 6" coil set up this weekend to try some new tests.
> Based on
> tests with my small 3" coil, I used two toroids this time.  The 40"
> mounted
> on the coil, with a 14" tall x 20" wide hollow cylinder made from
> aluminum
> roof flashing for a spacer with the 33" toroid sitting on top of this.
> The
> idea here is to get the discharges to go up and out and stay off the
> strike
> rail.  I also made up a new switch system for the resistive bank in
> parallel
> with the welder.  It is now variable from one 2000 watt element (about
> 22
> ohms) to 3.3 ohms with all elements in the circuit.  There are 6 total
> elements.  This is all an attempt to get the primary back in to
> synergistic
> tune which I lost last year when I rebuilt the primary set up and
> replaced
> all the interconnect wire with 3/8" copper tubing.
> 
> I had the rotary speed set down quite low for this first test.  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:
        That must have created several interesting ah, comments when you
found
that it had failed.  That's really a kick in the head to loose two of
those.  Just for information, I received one of the CP caps, .025
mfd.-at-20,000VAC on 12/28/95 with the 1/2-13 threaded studs which I
believe makes it part of the first special order Scott put together.  I
ordered direct since I joined the list just after the first order went
out.  I have run this in my 8" coil for some pretty long runs at 450 BPS
maximum, with no failure yet.  This year I have at most 25-30 seconds of
run time on it (sad to say it) with my brand new Plastic Capacitor's .05
mfd -at- 30,000VAC cap, running in parallel. I would be happy to give you
an update in 2-4 weeks when I have accumulated some decent run time.  
Just for information, the Plastic Capacitor's case is a rectangle which
I prefer--cleaner installation.  I place my capacitor's on a 1/2" thick
sheet of acrylic plastic, which is something CP does recommend by
default--their case has a 10,000 VAC max rating stamped on it.  Did you
have your cap on an extra layer of insulation?  Hope CP stands behind it
for you.

Chuck Curran
Cedarburg, WI