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# Streamer Length Calculations

Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>
Hi All,

`Part of the reason for the small SISG test coil and then the whole
``SISG thing was to figure out streamer propagation and distance
``calculations. Even though I wait eternally for more parts to arrive,
``"some" data is coming in now ;-))
`
There appear to be "two" factors controlling streamer length.

`The first is the top terminal energy (basically much like top
``terminal voltage) given by (I am just pasting the C-code):
`

`LeaderLength_E = LeaderLengthVsecFactor * sqrt(0.5 * VCsec_max *
``VCsec_max * (C2 + C3))
`
LeaderLengthVsecFactor = ~~ 36.0
C2 = secondary capacitance
C3 = streamer capacitance

`This is the peak top terminal energy stored in the secondary
``capacitance and steamer capacitance.
`

`The second is our old friend the Freau equation but based on actual
``delivered streamer power now:
`
LeaderLength_P = LeaderLengthPowerFactor * sqrt(Estreamer * BPS)
LeaderLengthPowerFactor = ~~ 2.0
Estreamer = actual joules delivered to the streamer load
These "two" factors give "two" lengths. You "get" the "LOWEST"!!!

`If you don't have enough top terminal energy (basically much like top
``terminal voltage), more power just makes hotter arcs, not longer
``ones. This is why increasing the BPS only helps a little in most
``cases even though the delivered power can be very high. If you have
``a 1000BPS 10kW coil that arcs 1 foot, you need more top voltage.
`

`If you don't have the delivered power, then 50 million volts on the
``top terminal does not help either. This is why coils made to have
``very low secondary capacitance to get to super high voltage choke
``out... A 1 million volt Tesla coil with 2 watts of input power, is
``not going anywhere...
`

`Hopefully the relationship and why "higher BPS" just does not go as
``far will be understood soon now... Since BPS is now a factor, it
``should probably be "scanned" too...
`

`Arcs to ground are pretty simple. You just zero the secondary
``voltage and dump all that secondary energy into the secondary
``resistance as a bright arc. They occur in probably "less than" 10nS
``(!) so just as fast as the program can dump energy...
`

`For arc to ground distance, if the normal air streamers are say 30
``inches, the arc to ground is about 40 inches. So there is just a
``factor of about ~~1.3 there of air arc vs strike distance. How
``"long" ground strikes last is a bit of an issue... More testing
``needed there. Basically how "long" the secondary is "connected" to
``ground... Seems like about 5 cycles in some cases. Probably should
``be based on energy left in the coil system or something...
`
Streamer capacitance is also pretty easy based on simple tests as:
C3 = (LeaderLength - TerminalDiameter) / 6.0 * 1.0e-12
The 220K constant streamer resistance seems to be holding rock solid!!!

`All the Rprimary, Rsecondary, Coupling, tuning, dwell time, L's and
``C's are trivial now and ScanTesla can tear through that in a short
``while... JavaTC knows the rest ;-))
`

`The SISG is wonderful since it eliminates so many variables as is
``perfectly repeatable!! I still need more data from "BIG" SISG
``systems like I am working on now to solidify the constants... It is
``sort of cool that we know so much about "lossy" coils that all the
``rest will just work out when their losses are added into the
``mess... I am "hoping" the DRSSTC portion will just work out happily
``too... The DRSSTCs lack of "fixed bang energy" made them "messy" to
``do these studies with...
`

`ScanTesla is being modified for the new models, forever tweaked, and
``now has a separate parameter input file so a minor adjustment to a
``constant just changes an input file rather than the whole base
``program. It is not available yet and won't be for maybe weeks as it
``is polished. If anyone "needs" the 'current' version, let me know.
`
BTW - For the "proper" lab setups to do this kind of work see these :o))))))
Main Lab:
http://drsstc.com/~sisg/files/BigSISGCoil/Lab1.JPG
Work Bench:
http://drsstc.com/~sisg/files/BigSISGCoil/Lab2.JPG
Work Table:
http://drsstc.com/~sisg/files/BigSISGCoil/Lab5.JPG
Cheers,
Terry