RE: Secondary size

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

Original poster: Jim Lux <jimlux-at-earthlink-dot-net> 

At 12:00 PM 1/16/2004 -0700, you wrote:
>Original poster: "Luke" <Bluu-at-cox-dot-net>
>
>So telling me to make it tall enough to avoid strikes is good and I knew
>that before I ever asked.  But very few seem to actuall tell HOW they
>figured that tall enough value out in the first place.

HV design is exceedingly empirical.  Spark propagation and HV breakdown 
have a lot of inherent variability, which causes all sorts of aggravation 
for people who have to trade off things like physical size and cost.  There 
is an incredible amount of what is basically "tribal lore" associated with 
HV design, including such things as rules of thumb about creepage 
distances, required free air clearance distances from components, and all 
manner of things.

It's not something that is highly amenable to rigorous analysis, although 
the latest Finite Element models, made possible by cheap computer power, 
are helping a lot.  Still, though, when it comes to predicting whether 
something will breakdown, most designers include a lot of margin, and 
regret it when they can't.

If you want a good introduction to practical HV design in the theory sense 
(as opposed to building things and trying it for yourself), the Los Alamos 
report by William North titled "High Powered Microwave Transmitters" is a 
great starting point.  There are several copies on the web (including one 
at Terry's site:
http://hot-streamer-dot-com/TeslaCoils/OtherPapers/NorthReport/
) Lots of empiricism tied to theory in that report.

North is talking about systems where you have a "real budget".  For the 
usual coiler, where you're looking for scrounged materials and so forth, 
it's even more empirical.  It's not like you can call up the manufacturers 
of QwikForms or Sonotube and get the HV breakdown or RF loss 
characteristics datasheet.  Relatively few coilers have the resources to do 
a systematic investigation and publish the results, so you have to 
synthesize your design from a large number of point designs and their 
reported results, recognizing that a goodly part of performance is 
construction technique and workmanship.