>>From Esondrmn-at-aol-dot-com Thu Feb 22 14:15 MST 1996
>From: Esondrmn-at-aol-dot-com
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>Date: Thu, 22 Feb 1996 15:51:47 -0500
>message dated 96-02-22 10:44:06 EST, tesla-at-grendel.objinc-dot-com writes:
>>Jim Fosse described his current system, including:
>>>        cap:            0.0137 uF measured 
>>>                        10" by 96" rolled flashing and 0.060" polyethylene
>>>                        in transformer oil.
>>>                        I'm a little woried about blowing this with 15Kv.
>>Jim, I've built 6 similar caps using 60 mil poly, and every one eventually 
>>failed.  For 15 kv, you need 90 mil or better.
>I agree.  I lost two of these.  One at 12kv and one at about 10kv.  What
>voltage did yours fail at?  We need to get the instructions at the ftp site
>for building these modified to alert future builders as to the true working
>voltage.  I don't think they can be used above 9kv safely.
>Chip Atkinson,  If we get a consensus on this, can someone modify those
>Thanks, Ed Sonderman

You're not going to like this, but I was using 9,000 volt neon transformers 
in parallel.  I must admit, though, that the variac I was using was one that 
had the "tap" so that it put out about 140 volts when cranked wide open (do 
we run our coils any other way? :)

So I calculate 10,530 volts rms out of my transformers into the caps.  Most 
of my caps lasted about 1 month of heavy usage.  I did not have safety gaps 
set up across the caps, though I did use one across the transformers.

What I'm seeing is that the poly purchased on the East Coast seems to have a 
higher voltage rating than towards the west...maybe a different regional 

Anyway, I would set the limit for 60 mil poly purchased in Dallas Texas at 
7500 volts input.

I have built one poly cap with 90 mil poly which is on an infrequently used 
15 kv system and it has held up so far.


[ Sorry for not noticing the note to me.  I've been busy here.  Kristian
  Kukkonen maintains the FTP site.  He is at kukkonen-at-alpha.hut.fi
  -- Chip ]