Re: Capacitor Sizing for Power

["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>



Tesla list wrote:

> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<Mddeming-at-aol-dot-com>
>
> Hi All!
>
>         I just started working up the requirements for my 15/240 NST farm
> coil and decided to try the P=rate*0.5*C*V^2 method. using a SRSG -at-120 BPS. I
> have read that this is a "good ballpark figure" for minimum cap size needed
> to handle the power.
> Now 15KV*240mA= 2700 W Substituting gives us
> 2700=120*0.5*15000^2*C  or
> 2700=60*15*15*1E6*C which reduces to
> 3/15*1E-6=C  or
> 0.20uF=C = 200nF

Almost;
15000 * 0.24 = 3600W
equating down to = 26.7nF

> Using the resonance relationship to calculate the minimum capacitance:
> XL=2*pi*f*L=Xc=1/(2*pi*f*C)
> if R<<XL then Z=E/I ~XL
> XL=15000/.240=62500=377*L or L=166.8Hy
> Xc=1/(2pi*f*C)
> 62500=1/377C or 2.35625*1e7=1/C
> 4.244*1e-8=C or,
> C=42.44nF

Keep it simple;
1/( 2 * pi * Z * f ) = 1 / (6.28 * 62500 * 60) = 42.44nF = common resocap
equation.
Note, this equation does not take into account bps (the other does).

Using the resocap size and running 120 bps, the breaks will occur faster
than the
cap can charge to full voltage. Reduce the cap size, and you decrease the
charge
time. 26.7nF is the size required to charge the cap to 100% Vp. That's all
it is. It
doesn't mean you can't use the resocap size with the transformer. If you
did, you
would still charge to 96% Vp (~20kV). I think the word "minimum" is
confusing. To
me, it is the "maximum" cap size at a rated bps for full charge.

Hope I didn't muddy the waters,
Bart

>
> A difference of 470% is not close in my ballpark. Even doubling the value for
> LTR gives an error >230%
> Am I missing something obvious or am I just brain dead this week?
>
> Matt D.