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Re: Mini Coils and Streamer Quality

Subject:      Re: Mini Coils and Streamer Quality
       Date:  Wed, 28 May 1997 13:11:34 +1200
       From:  "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
Organization: Wellington Polytechnic, NZ
         To:  tesla-at-pupman-dot-com


Hi Greg, all,

<snip>
> >      This was fun! :)  I am going to increase the supply capability
> > to 100W (was around 40W) and try some more. The nice thing was seeing
> > the full range of TC-type discharges in table-top miniature without
> > wondering what was going to be struck next.
> 
> Congrats on the spark efficiency -- 40W/3" = 160Watts/foot !!
> 
> This is a useful data point on the spark length vs output power curve,
> showing clearly that the relation is non-linear, favoring shorter arcs
> and penalizing longer ones.  I'm still trying to come up with a model
> that could predict this curve, given that the current density in the
> arc is constant, and the dissapated power per arc surface area is also
> constant.  Any more thoughts on this?
> 
> -GL

I guess you've tried curve-fitting already, or do you need more data 
points? If so, I'll try and come up with some. I'm currently hampered
at high power levels until the CP caps arrive.

    I upped the converter power level no problem but the variable 
smps feeding it carked it (inductor needs a redesign for that power 
level). I'll bypass that and feed the transformer/rectifier from a 
variac in the next day or so. I'd be interested to see how well it 
does at the 6kV level with more power in the form of more BPS.

    Some coil info:

SECONDARY  (acrylic former)
Ds about 2"
Hs 7"
Dwire 0.3mm (copper)
Topload = couple of turns of thick bare copper wire (not shorted)

PRIMARY  (vertical helix)
Cp 3.9nF 6kVW (MICA)
Dp 4"
Hp 1/2"
Np 4 turns (bifilar wound 1.2mm Cu dia wire)
Gap: single tungsten tipped 1/2" electrodes

I also have an h/d=1  2.5"dia Litz secondary which was tried with 
this primary. It is currently being heavily coated with varnish as
it proved to be too short and not well enough insulated for the 
voltage production at Vp 6kV. With what tests were done, there didn't 
appear to be a lot of difference streamer length-wise but that could 
change.

Malcolm