Re: A Marx-like design

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

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>


This is very clever....
Here are some questions that strike me...
What's the loss across all those gaps... The IR loss will be low, because 
the gaps are short and the current high, but there's an irreducible cathode 
drop.  In arc welding (stick, not TIG or MIG), it's really hard to get a 
stable arc below 20V or so, and that's with a molten electrode on one end, 
implying that you're going to have 20-30V drop in each gap.

Each cap gets charged to around 300V (resonant charging, 120V input, etc.), 
so you're kind of stuck with a 10% hit there..  240V charging would help a 
bunch, because then you're just looking at 600V total on each cap, with a 
5% hit...  I'll bet there's some nice sweet spot where the hassle of 
voltage multipliers or transformers to get the per gap voltage up (to 
reduce gap losses) gets to be more than the improved performance.

An idea... if you use some sort of gas gap, or maybe even a suitable 
semiconductor switch, you might be able to get the "gap loss" down.. I've 
seen Marx configuration pulsers built with avalanche transistors, but I 
don't know if they have the power handling you need.  Does an SCR (or 
really, a 4 layer diode, because you'd leave the gate unconnected) have a 
fast enough "turnon" to work in this application?


At 01:27 PM 9/20/2002 -0600, you wrote:
>Original poster: "K. C. Herrick by way of Terry Fritz 
><twftesla-at-qwest-dot-net>" <kchdlh-at-juno-dot-com>
>
>For some time I've had an idea for a spark-gap-type t.c. with a Marx-like
>primary, I've fully laid it out on paper (on my HD, that is), and I await
>a time when my inclination to loaf may diminish.  My idea is to
>resonantly charge a set of capacitor-modules, from the mains and in
>parallel, then discharge them in series through the primary.  I've
>designed it with 20 sections, each to be charged to ~600 V, then
>disc