40 mil LDPE and 5kv Transformers?

From:  Joshua Resnick [SMTP:seraphim-at-WPI.EDU]
Sent:  Thursday, April 09, 1998 1:21 PM
To:  'Tesla List'
Subject:  Fwd: 40 mil LDPE and 5kv Transformers?

>From:  richard hull [SMTP:rhull-at-richmond.infi-dot-net]
>Sent:  Wednesday, April 08, 1998 8:22 PM
>To:  Tesla List
>Subject:  Re: 40 mil LDPE and 5kv Transformers?
>At 08:09 AM 4/8/98 -0500, you wrote:
>>From:  Steve Falco [SMTP:sfalco-at-worldnet.att-dot-net]
>>Sent:  Tuesday, April 07, 1998 5:55 PM
>>To:  tesla-at-pupman-dot-com
>>Subject:  40 mil LDPE and 5kv Transformers?
>>I am building some capacitors using .040" LDPE.  I was originally
>>planning on building two units and putting them in series to get an
>>adequate voltage rating. 
>>But now I find that the H&R trannies I am using really only put out half
>>the voltage they are spec'd for, i.e. really 2.5 kv each (without
>>resonating caps), rather than 5 kv (with resonating caps).  So, I am
>>wondering if a single layer of .040" LDPE will hold with two trannies in
>>series (5 kv total voltage applied).  This would let me use 1/4 the
>>amount of plastic, which is worth considering.
>>If I assume 400 volts per mil of LDPE, then 0.040 * 400 = 16 kv which is
>>slightly more than 3 times the applied 5 kv.  So, there would appear to
>>be a reasonable safety factor, even allowing for peak voltage.
>>Any opinions out there?  Will one layer take it or should I go for
>>multiple series caps?
>>	Steve Falco
>Series caps are always best, but the .040 poly whould do OK provided you
>hold your power down to under 2KW.  I have successfully used .040 up to
>7.5KV when holding power under 1KW.  I suggest a flat plate design for lower
>Richard Hull, TCBOR

I have two H&R's in series with my coil. My cap is 9 layers of 6mil poly
per dialectric sheet. The cap is an interleaved flat plate type.  I would
not recommend using one 40 mil layer. When coupled to a larger cap, between
.08uf and .1uf, the transformers have a resonant rise. This rise can be
detrimental,I really think that one 40mil layer is just below the safety
margin. You want this rise effect because it helps the gap to break down at
the lower H&R voltages. I found that the best gap is  a vacuum quenched RQ
gap with close spacings between the pipes. My cap is .12uf and at full
power (140v) variac input to the H&R's with 6 series gaps, the pipes need
to be set just less than an eigth of an inch apart.  Don't let this bother
you, the H&R trannies really perform despite what has been said about them.
My coil produces 5' sparks and runs at 77kHz.  Just go all the way on the
cap and make it BIG.  

    /\/\ ((____)) /\/\/\/\                     Joshua Resnick
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