Re: Marx Generator

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

Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>" <dhmccauley-at-spacecatlighting-dot-com>

 > Dr. Resonance, all,
 >
 > Wow, a 1 megavolt Marx generator sounds like an expen$ive project.
 > I do have a 140 kVp, 500 mA x-ray transformer that, with proper rec-
 > tification, would probably fit the bill :^) This oil-filled monster tips
the
 > scales at nearly 1000 lbs. and, with proper external ballasting, makes
 > for one heckuva Jacob's ladder driver. I know that the ratings of x-ray
 > trannies are for low duty cycle but I feel reasonable sure that my x-
 > ray tranny could easily handle 5 to 10 kVA continuous with NO problem.
 > I run my Jacob's ladder with the narrowest part of the gap at ~8" and then
 > the rails spread out to about 20" at the top and with the variac turned
 > to only about 60% of 240 volt input, it will easily break down the 8"
 > spacing and climb some 42" to the top where the rails are about
 > 20" apart. And this will draw a good 50 to 60 amps from the wall.
 > The underrated 240 volt, 30 amp variac gets hot long before the
 > transformer even starts to get warm while doing this.
 >
 > I suppose the most expensive part would be trying to obtain the
 > 10 to 15 identical >100 kV rated pulse caps. And I'm sure we're not
 > talking about a few hundred pfd each either - probably more like
 > at least several nfd minimum or a sizable fraction of a ufd.

Not really.  You can use TDK type doorknob capacitors which are rated at
40kV each.  Series three of them per leg (simple bolt on action), and you
have a 120kV capacitor.
True, 1 MeV marx generator would be a challenging project in the least.
Just the corona losses alone are staggering at 100kV.
However, a 500 to 600kV marx generator is definitely within reach of most
amateurs.  One individual i know of used only a few "C" batteries to charge
up a 400kV marx generator with
18-24 inch discharges ! ! !  He used a small flyback converter to up the low
voltage (12V) to 6kVAC, then used a Cockroft-Walton multiplier variant to
produce 60kVDC which was used
to charge up the marx generator.

A 500-600kV generator would well be within reach using a simple NST and
Cockroft-Walton intermediatary multiplier stage.

My current design will utilize a 13 (lucky number) stage marx generator
using Cera-mite 2700pF, 40kV capacitors and some nice home-depot drawer
handles as spark gap electrodes.
This is my first venture into high voltage multiplier circuits so I will
probably just start off charging my marx generator with a 15kV
full-rectified, filtered DC NST to charge up the circuit.
Then go from there.

The Captain



 > And then obtaining rectifiers that are sufficiently robust to handle
 > these kinds of voltages and reversal voltages from the discharge.
 > Not to mention the huge inductive filtering that would be required :^O
 > Sounds like it may be pretty well beyond the budgets of MOST
 > of us :^(
 >
 > And last, but not least, this would be EXTREMELY DANGEROUS !!
 > One mishapped zap would be literally comparable to being
 > struck by a lightning bolt! And the noise level of the discharge
 > would probably be comparable to the report of a 105 mm Howitzer!
 >
 > Maybe 1 MV is a bit high of a goal for a Marx generator for a
 > novice experimenter without access to a REAL HV laboratory :^/
 >
 > Sparking in Memphis,
 > David Rieben
 >
 >
 >
 >
 >