Re: Geek Caps and My calcs.

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi Ry,

Tesla list wrote:

> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<rblaisdell-at-juno-dot-com>
>
> So if Instead I use my 12kv potential tranny rated at the same 1.5kVA
> overun on the amps a little to get 2.0kva would make the cap a little bit
> more robust, due to the lower peak to peak voltage.
>
> Though I ran these numbers through "javammc" and it still comes out
> questionable, because the voltage rating is not double the input peak to
> peak I suppose, because when I put 15caps in the number in series it goes
> to say that it is excellent.

The temperature rise of the cap is where the reliability rating comes from.
It pulls in
power dissipation and cap dissipation factors which include many elements
(cap energy,
breakrate, cap resistance at Fres, etc.. - it's not simple reliability
equation soley
on voltages). As Terry mentioned, it may be best to look at the rms
current. I'd bet
the rms current drops considerably between a 10 vs. 15 cap srtring. JavaMMC
will
identify the rms current for you. Keep an eye on it and you should see a
relationship
between reliability (temp rise) and current.

> Will keeping the cap strings cooled via say a hi-flow fan or in dry-ice
> make them more robust?
> It seems that a cool cap is a better working cap since losses due to heat
> are offset.

If the outside feels warm, the inside is hot! They heat up on the inside
and dissipate
heat to the outside.  Cooling a cap won't doing anything for the internal
heating which
is going on. Preventing it from heating is needed. Meaning to design it to
handle the
current, which is the only way I know to keep caps cool.

Take care,
Bart