Re: Spark gap voltage transients

Hi Alwyn,
          You've hit upon the dilemma in primary layouts:

> Original Poster: "Robert Alwyn Jones" <alwynj48-at-tesco-dot-net> 
> This may be old news to some of you expert coilers. Here it is anyway. 
> I believe the Tesla secondary behaves as an open circuit transmission
line due
> to it distributed structure. In which case presumable the primary will behave
> similarly except that it s a much shorter transmission line and both ends
> appear to be shorted to the transients.  So that when the spark gap fires it
> excites the transmission line characteristics of the secondary and a damped
> osculation will be produced superimposed on what I will call the lumped
> parameter response of the L and C combination. OK so what. Well I had assumed
> that what looks like a damped oscillation in the voltage waveform was due to
> the stray capacitance and inductance of the interconnections and the C.
> Therefore this could be reduced by better connections and a C with a
minimum of
> self-inductance. Yes part of the transient my be due to that effect but the
> dominate one will be due to the transmission line characteristics of the
> primary. I don t think this has any major practical significance to the
> of a system, although it may be possible to minimise the power loss due this
> transient by selecting a particular primary configuration such as spiral or
> helical. 
> In the above I have ignored the power filtering. Particularly in the
> configuration were the spark gap appears directly cross the power input, any
> filtering circuits will be exited when the gap fires and the resultant
> transient may dominate the above effect. Presumable the configuration
with the
> C directly across the input is the preferred configuration for this reason. I

While the cap effectively filters very high frequency gap transients 
it does present the full primary ringing voltage to the transformer
terminals. I wonder just which is the better option?  I've spent a 
lot of time trying to decide. Both camps have blown transformers I 


> have always put a bit of series R in the power supplies lines to reduce the
> ringing of the power filter. A power supply filter trick is to put the R in
> parallel with the L to eliminate its DC effect and reduce its power
rating. The
> value being calculated such that the resonance is critically damped. It
has the
> disadvantage that the filtering performance is reduced. A lossy core material
> has a similar effect but difficult to design.
> Constructive comments anyone.
> Regards Alwyn