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Wow, This VARIAN Multiplier is really cool !!

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Ash Small

Thu Mar 21 2013, 04:41PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

teravolt wrote ...

good find, it has 17 stages at 30kv max so I think it is for 500Kv so you will need oil or sf6 to run it. You can make a power supply out of a ZVS

I'm guessing here, but when I was reverse engineering one, I was advised by members here that, although the capacitor ratings would imply it was capable of 100kV, there was probably a safety margin of x2, so it was probably designed for 50kV, which, by the same logic, would imply that this one was designed for ~250kV.

Are the two sides separate, ie does one side multiply the positive, and the other the negative, to give an output of (say) +125kV, and -125kV, or is it one continuous multiplier giving either + or - 250kV?

Edit: I've just re-read PM's post above, and she quotes '200kV' output max.

Proud Mary

Thu Mar 21 2013, 05:58PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

The complete apparatus - the driver plus Wallis VM stack - is specified as 180 kV + 5 mA. As I said above, the two meters on the Varian driver unit are calibrated to 200 kV and 5 mA FSD using data fed back from the stack.

Incidentally there are not 17 stages in the stack, but 8.5.

8 kV RMS input will produce an output bracketing 180 kV depending on load and frequency. I would guess that the driver unit increased its output voltage and frequency to compensate for C&W 'sag' under increasing load. For experimental purposes, 8 kV RMS 30 - 50 kHz at up to 100 mA would be a good place to start.

The 30 kV Suflex capacitor rating - 30 kV - is roughly 2.5 times the peak voltage corresponding to 8 kV RMS, as we would expect to see in reliably engineered equipment.

paris

Fri Mar 22 2013, 08:30AM

Registered Member #3042 Joined: Wed Jul 28 2010, 12:36AM
Location:
Posts: 121

what size caps are those and where would someone find equivalents?
I had a search only found 30kv ceramic

that thing looks great

Steve Conner

Fri Mar 22 2013, 10:49AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

I've seen Russian capacitors of similar ratings on Ebay. Mike Harrison used them for his Marx generator.

The unit is probably designed for use in air. The big corona rings wouldn't be needed under oil. Also there are no oil seals on any of the cables.

For fun, you could try powering it up with 60Hz from a NST. Since it has two AC inputs, it's probably a full-wave stack, which suggests you should connect one end of the NST to each input and the centre tap to the stack's ground terminal (probably the metal base plate?)

The output current would be greatly reduced, but you could still do some fun electrostatic experiments. I can recommend the packing peanut fountain.

Be careful when pulling arcs, as not all C-W multipliers are rated to survive this. The diodes may fail after a few good zaps. If there really are carbon comp resistors between the stages, that is a good sign, they're probably there to protect it from arcs.

Proud Mary, do you have one of these?

Proud Mary

Fri Mar 22 2013, 12:43PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Steve is right to say that this Wallis stack was designed to be operated in dry air at atmospheric pressure. The equalising corona rings are sufficient to maintain stability - a nice smooth electric field gradient - so long as the stack is connected to a suitable load.

With no load the stack is likely to flash over any way it can, and be ruined in the process.

A happy load will have an equivalent resistance of 36MÎ©/0.9kW i.e. 180kV/5mA.

If a higher resistance load is used, then (without the regulating functions of the right driver unit) the voltage might rise to the point of flash over, with likely damage to some of the diodes and perhaps some of the the capacitors too.

An electrolytic 'water resistor' could provide a good load if it is carefully made with good metrics.

the mad scientist

Fri Mar 22 2013, 05:33PM

Registered Member #3768 Joined: Tue Mar 22 2011, 12:46AM
Location:
Posts: 107

That is amazing, much better than the tree CWs I made when I was like 15 (three years ago now). I wish I had one like that.

MRMILSTAR

Sun Oct 04 2020, 08:06PM

Registered Member #62119 Joined: Sun Feb 04 2018, 04:59AM
Location: Cedar Rapids, Iowa
Posts: 136

I have a chance to buy one of these at a good price. Did you every figure out how to operate it? Did you ever find any more specifications?

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