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Re: Sparklength inquiry


  Greg -

  Please do not bow out. My humble apologies for a bad mistake on my part.
I have a copy and read Uman's book several years ago. To my chagrin when I
went back to page 215 I found that I had hilighted the 10^5 joules/m. 

  I have attempted to compare the Lightning parameters in Uman's book with
a typical Tesla coil using the JHCTES program. The coil is 60 KW with a 10
meter (32.8 ft) spark length. This coil is similar to your 55 KW coil
described in the TCBA News Vol 10, #2, page 14. 

                    Uman                Typical
                    Lightning           Tesla Coil

  Kvolts/m          1000                316
  Surge Z/m         100                 2434
  Amps              10^4                130
  watts/m           10^10               4.1 x 10^7 
  time usec         10                  10 
  joules/m          10^5                410

  KVs = 65 x (32.8 X 12)^.65 = 3160/10 = 316 KV/m
  Surge Z ohms = sqrt(ls/Cs) = sqrt(.0646/109X10^-12)
               = 24344/10 = 2434.4/m
  Amps = V/Z = 316 000/2434.4 = 130
  Watts = V x A = 316000 x 130 = 4.1 x 10^7/m
  Joules = W x t = 4.1 x 10^7 x 10^-5 = 4.1 x !0^3/10 = 410/m

  It is obvious that with only 410 joules/m compared to 10^5 joules/m that
the Tesla coil is a puny electrical device. This is very evident in the
appearance of the TC spark compared to the lightning spark. However, this
is only a 60 KW TC. Someday, someone will build a monster coil. And to
think that just a few years ago a 10 KW coil was considered a monster. 
 
  The voltage KVs is a key parameter because the other parameters above
depend on this voltage. This KVs/m reduces as the input watts to the TC are
increased. This KVs in turn is dependent on certain other TC parameters
such as the TC pri volts (Vp), the pri cap (Cp), the sec coil inductance
(Ls), the sec cap (Cs). BPS, etc,  and other parameters. The JHCTES
computer program coordinates all of these parameters to end up with an
input watts to spark length program.

  I would be interested in your comments.

  John Couture

---------------------------

At 05:39 PM 9/25/98 -0600, you wrote:
>Original Poster: Greg Leyh <lod-at-pacbell-dot-net> 
>
>> Original Poster: "John H. Couture" <couturejh-at-worldnet.att-dot-net>
>
----------------------------  snip
 
>
>>   It should be noted that the square root curve flattens out and ends up
>> with very little increase in spark length regardless of power input. This
>> would make a lightning bolt a couple miles long almost impossible? The
>> average lightning bolt has about 150 joules of energy.
>
>
>150 Joules???!!!  Perhaps an umbrella is all you need after all!
>
>See Page 215, 'Lightning', by Uman.  
>The typical energy in a strike is approximately 100kJ/m.
>Therefore a 2 mile strike would therefore dissipate about 
>_322 MILLION_ Joules.
>
>I'm beginning to think that this thread is 'flame bait',
>and so I will bow out at this point.  The book is very
>good reading, you should pick up a copy.
>-- 
>
>
>-GL
>www.lod-dot-org