Re: Parallel and Series LCR Circuit Qs

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

Can you set an epsilon for the line?   Maybe segments of line separated by
ideal perfect line with L/C = 1....

----------
> From: Tesla list <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: Parallel and Series LCR Circuit Qs
> Date: Thursday, August 10, 2000 6:03 PM
> 
> Original poster: Terry Fritz <twftesla-at-uswest-dot-net>
> 
> Hi Jim,
> 
> 	I played with this a little today.  I would think a low value (~100 ohm)
> resistor but the 220k ohm of the streamer really is dominant.  
> 
> I have trouble with the arc speed.  The "per length" values are easy but
> MicroSim like to calculate the propagation speed down the line as:
> 
> TD = LEN x SQRT(L x C)
> 
> Given real numbers, a 2 meter arc is 6.2nS which is correct for a T-line
> but far faster than a slowly reaching arc.  Not sure how to trick it,
> yet...  If you go to a longer length line, it just compensates and gives
> the same net speed...  Working on it...  It is also very slow calculating
> but that is not a big deal...
> 
> Cheers,
> 
> 	Terry
> 
> 
> At 12:30 PM 8/10/00 -0700, you wrote:
> >and, as I think about it.. what sort of load would you put at the far
end of
> >the transmission line?
> >A short?  An open? A resistive termination (representing the thermal
heating
> >of the air at the end of the leader)..
> >
> >There is some discussion in the literature of what happens when a leader
and
> >spark channel grows, then shrinks back (say, driven from a bipolar pulse
> >source).
> >
> >Probably a resistive termination.  You wouldn't want a reflection back
down
> >the line,even though, because the line has a significant resistive
component
> >(representing the heating of the air along the spark channel), the
> >reflection would be rapidly attenuated.
> >
> >-----Original Message-----
> >From: Tesla list <tesla-at-pupman-dot-com>
> >To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
> >Date: Thursday, August 10, 2000 12:20 PM
> >Subject: Re: Parallel and Series LCR Circuit Qs
> >
> >
> >>Original poster: "Jim Lux" <jimlux-at-jpl.nasa.gov>
> >>
> >>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
> >>>
> >>
> >>
> >>
> >>
> >
> 
>