Re: tesla coil powered marx generator

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

Original poster: Bert Hickman <bert.hickman-at-aquila-dot-net> 

Tesla list wrote:

>Original poster: "RIAA/MPAA's Worst Nightmare" <mike.marcum-at-zoomtown-dot-com>
>I have a question. Which is better for a 1-2 MV marx generator: 20 stages 
>with 100kv x-ray transformer (60hz) or 2 stages with a 1MV tesla coil 
>(~200khz)? Could stages be added indefinitely given enough insulation for 
>the output? I would definitely need higher frequencies to keep the 
>parts/caps smaller/more affordable.

Mike,

Neither. I'd recommend the following approach:
Make two Marx generators, and configure them as a bipolar Marx. This will 
reduce the maximum voltage stress versus ground, and will allow you to have 
a system that's less than half the height of a single 2 MV bank. Clearance 
to the surroundings is not a trivial issue at 1-2 MV. Use triggerable gaps 
at the bottom gap so that YOU can control when the units erect and fire and 
to insure that both erect and fire at the same time.

To charge the unit I'd recommend making a Vacuum Tube (VT) or solid state 
power oscillator to drive the primary of a loosely coupled air core step-up 
transformer. However, unlike a VTTC, the secondary side of the transformer 
does not need to be a tuned resonant circuit, since all we want to do is 
extract a controllable level of RF power via the secondary. The HV output 
will serve as a high voltage current source which, when rectified, can 
quickly charge your Marx banks. And because it's operating at a high 
frequency, you have the option of using lower output voltage and voltage 
multiplication (i.e., dual + and - Cockroft-Walton multipliers) to provide 
+/- HVDC to charge your Marx banks. The operating frequency can be much 
lower that 200 KHz - even 20 kHz would be more than adequate, so you can 
use almost any style HV rectifiers. You shouldn't need a huge amount of 
power - 250-500 watts should be more than sufficient to easily power the 
pair of Marx generators.

By adjusting the plate voltage to the VT driver, you can control the peak 
charging voltage. If your plate voltage is 3 kV, use a transformer turns 
ratio of ~40:1 (or ~20:1 if you use 2X voltage multiplication). Since the 
system is not resonant, the exact ratio is not at all critical. You can use 
X-ray rectifiers (under oil) or build your own HV rectifier stacks. You may 
also want to run each HVDC output into a small HV filter cap and then 
through a water resistor to the Marx banks. These HV RC filters will help 
protect your rectifiers from backfeeding transients when the unit fires. 
The water resistors are a weak solution of CuSO4 dissolved in DI water 
filling a length of flexible vinyl tubing, with a copper terminal at each 
end. Alternatively you can mechanically disconnect your charging supplies 
via oil-immersed HV disconnect switches prior to firing the system.

BTW, I assume you are also planning build a Faraday cage around this 
beastie so that you don't trash your home's (and your neighbors') 
electronic devices from the EMP... :^)

Best regards,

-- Bert --
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