Re: Parallel and Series LCR Circuit Qs

["Jim Lux" <jimlux-at-jpl.nasa.gov> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Hmmm.. what about modelling the spark as a transmission line.  Scaled to a
length so that the propagation takes the right amount of time.  Just as in a
transmission line with an impulse, the source driving it doesn't "see"  past
where the propagation has gotten to.  So, it would appear to have a steadily
increasing C, as the step function propagates down the line....

The series L per unit length would be 1 uH/meter (roughly) and the C per
unit length is 5-6 pF/meter (roughly), so the characteristic impedance would
be sqrt(L/C) or 500 ohms...

The propagation velocity of a spark is around 1E7 m/sec, so your
transmission line would need to be scaled to 30 times the real length
(3e8/1E7), for a scaled L of 10 nH/meter and scaled C of .05 pF/meter
(keeping the impedance the same...).  I'll bet you could work the
series/parallel R in as well....

you could even get fancy and hook up a bunch of transmission lines in a
forked pattern, more representative of real sparks.

This might start to have time domain properties that are realistic in a
simple SPICE type model.

-----Original Message-----
From: Terry Fritz <twftesla-at-uswest-dot-net>
To: jimlux-at-jpl.nasa.gov <jimlux-at-jpl.nasa.gov>
Date: Wednesday, August 09, 2000 11:33 AM
Subject: Re: Parallel and Series LCR Circuit Qs


>Hi Jim,
>
>At 06:24 AM 8/9/00 -0700, you wrote:
>
>>> So the Tesla coil "source" basically needs to be impedance matched to
>>> supply this "load", optimally.
>>
>>Of course, the impedance is time varying too, with the C growing as the
>>streamer grows....
>>
>
>Yes!  I assume the coil should be optimally matched when the streamer is
>longest since that is were every bit of energy needs to be to push the
>streamer that little bit further.  If a coil is matched for a 10 foot
>streamer, it will not mater if the matching is poor at 1 foot.  It will
>have no trouble getting past one foot and on to were every little bit
>counts out at 10 feet or the edge of it's available power where fine tuning
>really counts.
>
>Of course that "may" not be theoretically the 'best' point considering the
>other dynamics going on.  But it is my best guess...
>
>Cheers,
>
> Terry
>