Re: Lower secondary cself => better performance?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <twftesla-at-uswest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
> 
> Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<Gary.Lau-at-compaq-dot-com>

> The total secondary capacitance Csec occurs in two components - the Ctop
> from the toroid, and Cself, the distributed capacitance of the secondary
> windings.  When a streamer breaks out, the charge from Ctop is there with
> just the metal in the toroid between the Ctop charge reservoir and the
> streamer where it wants to go.  But the charge in Csec is distributed along
> the length of the secondary.  There are many mH of inductance between most
> of this charge and the streamer that wants to drain it.  The streamer is a
> very high frequency, short-lived event, so the intervening inductance just
> won't allow it to be useful in terms of feeding the streamer.  So it is
> desirable to have as large a portion of Csec in the form of Ctop and as
> little as possible in the form of Cself. 

I agree with this, but for arcs to ground. Streamers, maybe except
for an initial forming transient, become part of the whole system.

> I think this is why space wound
> secondaries are sometimes favored, as it minimizes Cself (in addition to
> lowering Rac and raising the Q) of the secondary, though I've heard of no
> direct experimental performance comparisons.  

The self capacitance of a coil depends almost exclusively on its
dimensions. The number of turns or the spacings in the windings have
little effect.

> When streamers occur may be one (important!) instance where the lumped model
> of the secondary may not accurately describe what happens should charge be
> drained from Ctop to a streamer, but "stranded" in Cself.

The formation of arcs that drain all the energy of the terminal have
really no relation with the secondary coil. They are DC sparks.
Streamers that don't connect to the ground appear to transport currents
with the same frequency where the system oscillates, and are affected 
by the dynamics of the two coils system.
 
> I'm not sure that maximizing the theoretical peak pre-breakout secondary
> voltage is useful in maximizing streamer length.  Maximizing the efficiency
> of getting the total energy stored in the secondary to the streamer is.

I can't see a better method than using a large enough terminal to have
energy available, and adjusting the tuning so the capacitive load of the
streamers is taken into account. For streamers, this later condition is
more important, but a large terminal causes the ideal tuning point to
be less sensitive to the streamer loading.

Antonio Carlos M. de Queiroz