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Re: Sizing capacitors



Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi,

At 11:53 PM 6/16/2006, you wrote:
Thanks, Terry!  Very helpful as usual.  I suppose my
doubts about the transformer <==> capacitor
formulation come about because it seems to me that a
capacitive load on the transformer is going to have a
crummy power factor, thus rendering the transformer VA
incompatible with the coil Watts value.

Is that true?

Yes, but power factor really only concerns nice sine waves. In a Tesla coil charging DC capacitors, the waveforms are distorted. The power factor will be pretty low in any case. A clamp on RMS ammeter would tell you the current which should be 1.67 amps for 200VA.

In other words, to use 290nF would mean
200W effective power from the transformer, but the VA
would be higher, right?  If I'm way off, just shut me
up! :-))  Otherwise, what I guess I was asking was
this:  How would one go about choosing a cap for a
given VA, or otherwise so as to avoid exceeding some
rated peak current.  Again, this is a PT and probably
can take a few times its rated 200VA...guess I'm just
interested in "getting the math" instead of surviving
on "rules of thumb" as I have for years now.

It would have to be modeled with a circuit simulator like MicroSim:

http://hot-streamer.com/TeslaCoils/Programs/1-91pspstu.exe

A model like this could be modified to do it (needs MicroSim to open):

http://drsstc.com/~sisg/files/SISG-coil/MicroSim/SISG-terry-Small.sch



Regarding "resonance" and "DC"...duh!  My brain was
obviously already in bed when I went off on LTR/STR.
I'd actually *love* to know how those values were
computed for NSTs, etc., but if you recall sending it
to the list or posting it somewhere, I'll just look
harder :-)

http://hot-streamer.com/TeslaCoils/Misc/NSTStudy/NSTStudy.htm

Cheers,

        Terry



Good night (for me!) -
Aaron, N7OE

--- Tesla list <tesla@xxxxxxxxxx> wrote:

> Original poster: Vardan
> <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>
>
> Hi,
>
> At 10:14 PM 6/16/2006, you wrote:
> >I've built coils before using caps that were
> obviously
> >"way STR" (e.g., 30nF on a 15kVA pig), and so never
> >bothered to really understand how one sizes a cap
> to.........