Re: desirability of high coupling...Re: primary INSIDE of secondary?

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

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

Tesla list wrote:
 >
 > Original poster: "Jim Lux by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
<jimlux-at-earthlink-dot-net>

 > 1) With respect to "efficiency", defined as the amount of energy lost to
 > resistive losses. Is the loss of the primary or secondary higher? The
 > primary cap has more loss (in a percentage way) than the secondary (which
 > has air dielectric, and is very low loss).  I'm not so sure about the
 > primary L vs secondary L, but off hand, I'd just think the primary L is
 > lower loss than the secondary L.  Considering the entire primary circuit,
 > the spark gap is probably the big loss, so high coupling gets the energy
 > out of the primary quickly, reducing the spark gap losses...

This is certainly an important point. Cool gaps lead to more voltage
in the primary capacitor and easier quenching. The gap in a coil with
high coupling works more uniformly and with less heating.

Another important advantage of high coupling is that tuning becomes
less critical, and so the presence of streamers don't detune the system
excessively.

 > 2) There is a huge effect on spark growth and shape from the RF envelope,
 > and the coupling (and relative tuning) of pri and secondary.  It's possible
 > that you don't want too fast a rise of the RF energy in the secondary, to
 > give the sparks time to develop and lengthen?  Consider that a Marx bank
 > with a single impulse is sort of a similar thing to a very highly coupled
 > TC (i.e. all the power is there at the first RF cycle)... Marx banks
 > generate sparks that look very different from a TC.  (Has anyone built and
 > tested a 120 pps reprate Marx with a couple hundred kV output?  At first
 > glance, one might expect the output to look like a TC)

I imagine that a Marx bank, or any other DC HV generator, would not
produce streamers, that require RF current in the channels started
as corona. Arcs with complete terminal discharge look almost the same
for any generator.

 > 3) Part of the coupling thing is the relative resonant frequencies of the
 > primary and secondary (leading to "beats" (aka "notches"))...again, this
 > affects the RF envelope, which probably affects the spark "look".  There's
 > also a change in the resonant frequency of the secondary as the spark
 > develops...

The effects of the envelope on streamer development are still
mysterious,
I think. The detuning when the streamers develop may be not a so serious
problem if the coupling is high. And even with low coupling, the system
may "tune itself" to a certain average streamer length.

Antonio Carlos M. de Queiroz