Tesla generators run at microscopic current levels. Its the RF current that
often destroy caps in amps.
Carl
KM1H
----- Original Message -----
From: <ToddRoberts2001@aol.com>
To: <amps@contesting.com>
Sent: Wednesday, March 17, 2010 1:28 PM
Subject: Re: [Amps] Teflon Caps
> Tesla Coil builder sites are good places to read about different
> builder's experiences with high voltage caps.
>
> Their advice is to limit the voltage across each capacitor to no
> more than 5KV. Many of them are using Polyethylene sheet as
> insulation for their high voltage caps and they recommend
> immersing them in oil. They subject their capacitors to tremendous
> peak voltages and currents as most Tesla coils are based on spark-gap
> generators of RF. Their capacitors are all fixed ones though, not
> variable.
>
> Nowadays many Tesla Coil builders have switched to Multi-Mini-Capacitors
> or MMCs. These are strings of 1500 - 2000 volt DC rated polypropylene
> caps wired in series-parallel. They said it is best to use the metal
> foil/film types
> and not metallized/film types.
>
> They say that if the voltage is 5KV or less Corona is usually not a
> problem.
> Also some companies do make grades of Teflon that are highly Corona
> resistant so a lot
> depends on the grade of Teflon used for a high voltage capacitor.
>
> So far I have had good luck building trombone-style high voltage variable
> capacitors for a transmitting loop antenna using a thin sheet of Standard
> Teflon
> wrapped tightly over copper pipes that slide inside slightly larger copper
> pipes
> for the loop tuning variable capacitor. This would probably work even
> better with
> modified-grade Teflon but don't know how expensive that stuff might be.
>
> So far no flashovers or any problems with heating at a calculated nearly 4
> KV RF
> in the loop and 8 amperes of RF current using standard Teflon sheet. Very
> inexpensive to build. Teflon makes very high Q low-loss capacitors needed
> for a
> transmitting loop.
>
> 73 Todd WD4NGG
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