Re: Mini Coils and Streamer Quality

To: tesla-at-poodle.pupman-dot-com
Subject: Re: Mini Coils and Streamer Quality
From: Tesla List <tesla-at-stic-dot-net>
Date: Fri, 30 May 1997 02:02:30 -0500
Approved: tesla-at-stic-dot-net
Subject:      Re: Mini Coils and Streamer Quality
       Date:  Thu, 29 May 1997 12:00:39 +1200
       From:  "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
Organization:  Wellington Polytechnic, NZ
        

>   From:  richard hull <rhull-at-richmond.infi-dot-net>
>     To:  Tesla List <tesla-at-pupman-dot-com>
> 
> 
> 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.
> >     Based on this, I would say that if your BPS is still rather low
> >and the sparks assume something of a "crackling" quality, try upping 
> >the break rate before increasing input voltage. I was amazed at how 
> >little dependence there was between cap voltage/energy and attached 
> >streamer length.
> >
> >Malcolm
> 
> Malcolm,
> 
> Your last sentence said it all.  The power is the thing.  We were using
> .01ufd total system cpacitance on maggey 11-A and just upping our rep
> rate
> to get 100" sparks! Now I am using a .03ufd cap, lower rep rate, and
> higher
> inductance resonator coil and hitting 124" with similar KVA ratings. 
> The
> spark won't necessarily grow with increased capacity in the tank.
> 
> Richard Hull, TCBOR

I am homing in on a useful guideline for best coil-size vs spark and 
power efficiency in the 2-coil system.
     Coil size: it is clear that the higher the primary energy, the 
greater the output voltage. At some point, the windings will break 
down or the thing will send sparks directly from top to bottom. At 
this point, Vout is optimized (if backed off a little). From there,
the best you can do is up the break rate until (a) either the power 
source is sagging so badly that Vp is way down, or (b) so much 
ionization is going on in the output spark that Vout sags badly.
     Power efficiency: reactive charging is a must to get best power 
factor with a minimum in the circuit. Also, the shortest allowable 
dwell for the k the system is set at must be made to happen to give 
the power supply maximum time possible to charge the cap.
     
     It seems clear from my experiments that one can get humungously 
long sparks without running the coil anywhere near its highest Vout 
before the windings breakdown or flashover. Coil height has to be 
dictated by the highest Vout to be used. I've found in practice that
single shot highest Vout is too high for repetitive operation because
of the extra ions floating around the coil with the repetitive action.
 
A few more thoughts,
Malcolm