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Re: Why does top capacitance work?
Tesla List wrote:
>
> Subscriber: lod-at-pacbell-dot-net Sat Feb 15 14:25:24 1997
> Date: Thu, 13 Feb 1997 22:26:05 -0800
> From: Greg Leyh <lod-at-pacbell-dot-net>
> To: tesla-at-pupman-dot-com
> Subject: Re: Why does top capacitance work?
>
> Bert wrote:
>
> > Steve,
> >
> > It turns out that adding capacitance to the top actually reduces the
> > maximum output voltage that the coil can generate! However, adding a
> > toroid-shaped top-load can prevent the secondary from starting to
> > break-out with corona/streamers until a higher voltage is reached. This
> [snip]
>
> > -- Bert H --
>
> Bert,
>
> Doesn't this apply only to the very first gap firing, when the power is
> first applied? After that, the first streamer would adversely compromise
> the holdoff voltage of the toroid, acting electrically as a long needle
> that projects from the toroid. The subsequent gap firings appear to only
> build upon the initial streamer, unless the gap rate is so low that the
> ions start to re-combine between gap firings. This results in a large
> number of small streamers.
>
> I am still mystified as to why a large toroid makes a difference. My
> favorite explanation is that the addition of a huge toroid forces the
> operator of the TC to add capacitance to the primary, for tuning purposes.
> More capacitance increases the thruput power, which is always better.
>
> -GL
Greg,
You certainly make some compelling points. I agree that the "root" of a
streamer, once formed, will act as a weakenned area during subsequent
bangs, since it's the area of highest current density and should have
the greatest degree of thermal ionization. The advantage a large toroid
may provide on higher-impedance coils may come from providing a low
impedance energy reserve (i.e., a capacitor to ground) during the time
that the streamer is re-propagating along the weakenned path blazed by
its predescessor. Adding larger capacitance will provide a
proportionately larger reserve of energy once the voltage rises to the
point where reignition occurs. The fact that there seems to be little
benefit on your large coil may be due to it's relatively low impedance -
it doesnt need any help, and adding the toroid merely reduces peak
voltage. Ultimately, it IS power which governs ultimate streamer length.
Certainly your last point is true, although Wysock and Cox's coils tend
to have BIG tank caps, small primary inductance and small top
dischargers -- Adding tank capacitance alone seems to be sufficient for
BIG streamers on larger coils.
Looks like there are still lots of mysteries to be solved! BTW, what do
you do for a living that lets you play with these nice toys?? :^)
-- Bert --