Re: OLTC II Initial calculations

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <teslalist-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Stephen,

On 8 May 2003, at 7:28, Tesla list wrote:

 > Original poster: "Stephen Conner by way of Terry Fritz 
<teslalist-at-qwest-dot-net>" <steve-at-scopeboy-dot-com>
 >
 > At 17:32 07/05/03 -0600, you wrote:
 > >Original poster: "Malcolm Watts by way of Terry Fritz
 > ><teslalist-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>
 > >
 > >Hi Stephen and other output voltage enquirers,
 > >                                                It is well known that
 > >you cannot judge output voltage by spark length in a disruptive TC.
 >
 > In the calculation that I posted, I didn't do that. I used John's spark
 > length formula (I figured it would work since it was one of his coils :) )
 > to work back fron his quoted spark length and find the power. Since he also
 > quoted the bps, I could find the bang energy. From the dimensions he posted
 > I had a rough idea of the secondary capacitance and so could work out the
 > output voltage from the bang energy and capacitance.
 >
 > >I'd urge anyone who
 > >wants to see this for themselves to do some single shot expts.
 >
 > I have been doing these with my OLTC. I designed it to be adjustable from
 > 2bps to 1200bps. Basically I found that at low breakrates the spark length
 > agrees well with the peak output voltage and the dielectric strength of
 > air. (The 1.1kV/mm thing) Beyond about 300bps the sparks start to grow
 > until at 1200bps they are about 12".
 >
 > With bigger coils, the streamer growth obviously starts at a lower bps. My
 > larger coil did about 10" on single shots, 17" at 100bps, and 30" at
 > 400bps, with roughly the same bang energy in each case.

I have a coil which produces about 11" attached sparks at a breakrate
effectively = 1 and 5' attached sparks about 25% of the time at a
breakrate which randomly varies between 100 and 200. Single static
gap with finely tuned airblast. Theoretical lossless output voltage
is about 400kV. In reality it is probably closer to 300kV. Primary
energy is about 4 - 4.5J.

Malcolm

 > All measurements are the longest distance it will jump from a breakout
 > point to a grounded point, at least once in a 1 minute test.
 >
 > Steve C.
 >
 >
 >
 >
 >