[Prev][Next][Index][Thread]

Re: Fw: Arc Impedance Study - Computer Models

Hi Terry, all,

> Original Poster: Terry Fritz <terryf-at-verinet-dot-com>
> 
> At 01:12 AM 10/11/98 -0400, you wrote:
> >Hi Terry,
> >    Nice analysis.  There was one last problem.  What is the best
> >surge impedance for the primary?  This is related to the many turn VS
> >few turn primary which is related to the question: Is it more
> >efficient to transfer the energy to the secondary system with a single
> >soliton like pulse or to let it transfer slowly by sloshing back and
> >forth?  Would a pulse forming network delivering a precise rectangular
> >pulse with a period just shy of one quarter of the secondary resonant
> >period be more efficient?
> >
> >Barry
> >
> snip
> 
> Hi Barry,
>     So... is a many-turn high-inductance primary better or worse than a
> few-turn low-inductance primary.  This is very difficult to measure in real
> coils since changing the primary inductance does the following things:
> 
> 1.  The coupling will change.
> 2.  The primary capacitance will increase.  This will raise the primary
> energy unless the voltage were to be turned down to compensate.
> 3.  The primary circuit resistance will change.
> 4.  The spark gap may act differently depending on how much current goes
> through it.
> 5.  Just visually looking at the coil's streamers after major circuit
> changes over time is not an exact science :-)
> 
> Models, however, can easily test such a change while locking all the other
> variables.  The output of computer models is, of course, perfectly
> repeatable and objective.
> 
> This test assumes only the primary capacitance and inductance changes.
> Coupling, primary circuit resistance, and spark gap effects are locked.  I
> will add a correction at the end for the difference in primary enegery
> larger caps have.
> 
> Primary Corrected               Corrected
> Inductance  Peak Current    Burst Time  Relative Power
> 25%     492         61      3.24
> 50%     622         61      5.19
> 100%        719         61      7.17
> 200%        782         61      8.21
> 400%        814         61      8.91
> 
> So it appears that larger, high inductance primaries are better.  The
> graphs show that low inductance primaries tend to have a single burst while
> high inductance primaries have multiple bursts.  However, more energy is
> being delivered to the arc with the high inductance primaries.  I suspect
> the losses are killing the performance with the larger primary currents.
> 
>     Terry

Agree with your analysis completely. I also have an observation to 
add: I have empirically found that the lower the surge impedance of 
the  **charging**  circuit, the more stringent the quench 
requirements. Speaking strictly about observed performance and not 
single notch quench:
       I run a large cap small Lp coil on quite modest primary 
voltages with a single static and get sterling performance with no 
gap cooling, airflow etc. However, running with a small cap and the 
same leakage-L limited transformer, the same gap does not do the job 
and requires the extras to perform. Anyone else found this? Resonant 
charging systems in particular seem to perform well with the simpler 
gaps.

Observations invited,
Malcolm