Re: max cap size? (fwd)

---------- Forwarded message ----------
Date: Tue, 12 Oct 1999 15:16:35 EDT
From: FutureT-at-aol-dot-com
To: tesla-at-pupman-dot-com
Subject: Re: max cap size? (fwd)

In a message dated 99-10-12 05:34:24 EDT, you write:

> i.e. each panel is 0.01uf and I can stack these together, (parallel), in
> any combination from 0.02 to 0.09uf.
>  is there a 'best' value to use or should I go for as high a value as
> possible? and why?
> I am nearly ready for first light.

> Kindest Regards,
>  Robin Copini in Oz >>


That will be a great coil.  A larger capacitor will give longer output
sparks provided the pig is able to charge the cap enough.  Your pig will
easily be able to charge a 0.09uF cap at your break rate, and should 
give you 15 foot sparks or so.  Is this the kind of spark length you're
looking for?  The larger the cap, the more power the coil will draw, and
the longer the sparks will be, since there will be a larger energy 
throughput occuring.  But if the cap is too large, there might not be
enough power available to charge it, and also, the coil may break
down from the monstrous bang size.  

I did a series of tests which showed that for the absolute max spark
length for a given input power, a low break rate is best (100 to 120 bps).
My tests were done at low power (200 to 1500 watts), so I don't know
if the results will hold at higher power levels.  I saw a 20% reduction in
spark length for a given power input when I increased the break rate
from 120 to 240 bps.  It is possible however that the sparks although
longer, might not be as bright at the lower break rate.  If a lower break-
rate is used, then the cap has to be larger to keep the power input the
same, unless you increase the cap voltage in some way....for instance
by using a higher voltage transformer, or by gaining voltage through
resonant charging.

Ideally, a coil should be designed starting from the desired spark-length, 
"backwards" through the toroid size, secondary size, bps, cap size,
and transformer size, etc.

John Freau