Re: Pool Pig...

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>

Hi Chip,

I think Greg pretty much covered the answer for you.
Also, 7200 volts is a bit toward the low side for high
powered coils as the SG contacts must be brought
quite close to reliably fire and when trying to switch
that much power in that small of a space, proper
quenching becomes quite a challenge, even with
rotary gaps. That's why 14,400 volt pigs are popular
amongst us pole pig coilers. Remember too, that with
double the transformer voltage, the capacitance can be
cut fourfold while maintaining the same energy transfer.
I believe list member Scot D. (aka- bunnykiller) uses 2
seriesed 14,400 pigs to fire his coil at a whopping 28,800
volts. His primary cap is only .057 uFd, I believe, but that's
the same energy available as with .228 uFd at 14,400 volts
and  .912 uFd at 7200 volts!

David Rieben

----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Sunday, November 19, 2006 7:21 PM
Subject: Re: Pool Pig...


> Original poster: G Hunter <dogbrain_39560@xxxxxxxxx>
>
> Hi Chip,
>
> The transformer / cap matching formulas often break
> down when pole pigs are involved for precisely the
> reasons you've just illuminated.  An optimal cap for
> 7200vac at 2 amps is just too big.  It's not a big
> deal.  Smaller-than-resonant caps are the norm at such
> power levels.  Start off with about 50nF and
> incrementally add capacitance until you get decent
> sparks.  Maxwell Labs 30nF 30KV plastic caps go for
> about $100 apiece on e-bay these days.  Try one or two
> of those to start with.
>
> Cheers,
>
> Greg
>
>
> --- Tesla list <tesla@xxxxxxxxxx> wrote:
>
>  > Original poster: "Chip Ford" <chipford@xxxxxxxxxxxx>
>  >
>  > Ok...there are many kinds of transformers out there.
>  > Seems that the
>  > really BIG coils use a pole pig. Such as "The green
>  > monster". His is
>  > a 15kva @ 14400 volts. Using the math KVA = ((VOLTS
>  > X AMPS) / 1000),
>  > I came up with an amperage of @ 1.042 Amps (15,000
>  > watts). Since .001
>  > Amps is equal to 1ma, he has 1042ma. According to my
>  > calculations,
>  > the resonant cap is @ .1919 uf. I think he said his
>  > cap was
>  > .1uf...close but not real close..Now, I think alot
>  > of the line
>  > transformers have a selector switch on them. I think
>  > they are like
>  > 7200, 6400, 5600 volts for the ones around here. So,
>  > if I have 15 kva
>  > transformer @ 7200 volts, it will have an amperage
>  > of @ 2 amps
>  > (2000ma)(15,000 Watts). At this rate, my cap is
>  > gonna be around .75
>  > uf. This is really high and from a few calculations
>  > that I have made,
>  > A secondary coil 12" 81/2" dia. 48" tall will need
>  > over 10000 turns
>  > of #39 awg. wire on it. This pretty much makes this
>  > transformer
>  > unusable. Besides that, where is a hobbest ever
>  > gonna find a cap? Am
>  > I missing something here? Are my calculations
>  > incorrect? Am I looking
>  > at the transformer incorrectly? Please
>  > comment...Chip Ford
>  >
>  >
>  >
>
>