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Re: Variacs, HV Jell, and LTRS Caps / oil for MMCs / Etwas trost

Hi GSTCs, Terry,

TF> Also, I am working on a new MMC cap design that will require 
    that they be submersed in oil.  
Be careful as the mineral oil will be perhaps somewhat aggressive 
to the housing of the caps! I destroyed my homebuild LDPE/oil-cap
before applying the first volt because the PS I used as 
compression plate and cover of the box got brittle due to the 
mineral oil and cracked all over.

TF> I am running them above their ratings (in the "enhanced"
    mode :-)) taking advantage of the fact that "I know things" :-))  
    Since oil is such a mess, I was wondering if mixing mineral 
    oil and say paraffin would produce a jell that could be heated 
    to flow but would solidify like grease when cooler?  The jell 
    would not be a dielectric but more of an insulator and mounting 
    medium to put the caps in nice PVC cases.  The advantage would 
    be it would not run, spill, leak, etc.  If this works, I can 
    make a 5.6nF cap for about $25!!  If it doesn't, I don't want 
    to have to clean up a bunch of oil :-))  This will test if the 
    manufactures ratings really do mean anything in Tesla coil 
    applications.  I am running just over the edge in voltage and 
    current but theoretically they should hold up very well.  
I think a fan should do the job. Just make a top and a bottom plate
and let the air blow through the rows.

TF> My present MMC runs soooooo cool I think it may be a waste 
    of money to over design these things too much.  More 
    exploration of their limits is called for.  Since I have all 
    my stuff modeled, I can predict RMS currents and voltages very 
    well so as to push the rating of the parts "gently"...
Still a problem is to tell how long a cap will last if it blows
not in the first hour or so. If it will be stressed over the limit
the 'time to death' will become shorter at least exponentially
with the 'overstress' because of the weakening of the dielectric.

Stefan
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