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Hello Ed, All
You wrote:
>Original Poster: Ed Phillips <evp-at-pacbell-dot-net>
>
>Example:
>
> The reactance of an 0.1 mfd capacitor at 100 kHz is about about 16
>ohms; if the Q is 100, the ESR will be about 0.16 ohms. If the RMS
>current in the circuit is 100 amps (a pretty high value), the total
>power loss due to ESR would be 160 watts. This shouldn't heat a
massive capacitor very fast. Real high-power experts - comments please.
Why do you say 100 amps of primary current is a lot? I would say this
is pretty low for coiling circuits:
I am presently running:
1.) a 25.5nF cap
2.) a 7.5kV/75mA NST
3.) Primary inductance is:37.85µH
Eq1:) J=0.5*C*V^2
Eq2:) J=0.5 *L*A^2
solving for A:
A = V* SQRT(C/L)
Vgap=7500*1.414 (peak V)
Lpri=37.85µH
A = 10606 * sqrt ((25.5*10^-9F)/(27.85*10^-6H))
= 10606 * sqrt(9.15*10^-4)
= 320.8 Amps
With a 7.5kV 75mA NST, I am certainly not running a high power coil.
My arc length is around 41". My final setup will be running 4500VA worth
of 7.5kV NSTs and a 100-120nF cap into a primary designed to resonate at
~98Khz. A rough calculation leads to around 1.5kA for this design.
So, I would DEFINATELY NOT consider 100A of primary current "big".
BTW:
My arc length pretty much fits John Freau´s calculation of spark length
= SQRT(VA)*1.7. This would be 53" in my case (not quite there yet).
On the other hand 41" is ceiling heigth at the moment (so I don´t know
if the arcs might be longer) and I am not running the max primary cap
possible (which would be around 32nF). And my toroid is too small
(4.3" x 10"). I get multiple streamers all the time. There is no pointed
object necessary to provide breakout. I get a 41" roughly every 15-30
secs of run time. These 41" discharges are white hot.
This once again leads me to believe a low voltage high current design
does NOT lose against a high voltage low current (of the same VA)
design.
Coiler greets from germany,
Reinhard