Prototype 180kV Power Supply

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Joe Gayo
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Prototype 180kV Power Supply

Post by Joe Gayo » Thu Jul 22, 2021 3:23 am

I was able to test the power supply I've been designing/building at the full voltage/power rating today on my fusor.

Here is a picture of the preliminary setup (the multiplier has a built-in voltage divider and current sense):
180kV.png
At the moment, I'm running "open loop" with the half-bridge inverter I designed and the feedback is read by two multimeters, but in the near future this will be a fully regulated (cc/cv) system.

I ran a number of tests today at -180kV and 7mA! The neutron levels continued to increase significantly from my 125kV max runs.

Some details:
10-Stage Full-Wave Multiplier Submerged in Dielectric Oil
50kHz ac supplied by two 180deg out of phase transformers (21:1000 ratio)
2.5 Gohm Voltage Divider, and Bottom Side Current Sense

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Mark Rowley
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Re: Prototype 180kV Power Supply

Post by Mark Rowley » Thu Jul 22, 2021 3:54 am

Impressive work Joe
I’m totally convinced multiplier circuitry is the future of fusor power supplies.

Mark arowley

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Joe Gayo
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Re: Prototype 180kV Power Supply

Post by Joe Gayo » Thu Jul 22, 2021 4:16 am

It seems the ions really are predominately D2+. With 180kV applied, the ions have the equivalent velocity as D+ at 90kV, therefore it makes sense why I'm still seeing significant gains. I'm really glad I took the time to reinforce my neutron/X-ray shielding. (On another note, I ran with helium and saw virtually no neutron counts from X-Rays).

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Richard Hull
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Re: Prototype 180kV Power Supply

Post by Richard Hull » Thu Jul 22, 2021 5:35 am

It is hard to imagine any significant number of intact molecules of D2 surviving in the confines of the high velocity maelstrom of 100kv differential fields in a cube fusor. The electrons in the mix would see to destroying the very weak molecular bonds, I would think. The mean free path in a small cube would exceed the dimensions of the device for both ions and electrons. Most all fast neutrals and virtually 100% of the electrons wind up at the walls. As the cylinder grids are a form of BOT in a cube, I guess the bulk of the volume could be really cool compared to a complex geodesic in a spherical reactor with many beams.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Joe Gayo
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Re: Prototype 180kV Power Supply

Post by Joe Gayo » Thu Jul 22, 2021 5:45 am

The pressure is quite high and there are probably quite a few collisions that are causing molecular recombination. At the very least there is significant velocity distribution among ions.

Cai Arcos
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Re: Prototype 180kV Power Supply

Post by Cai Arcos » Thu Jul 22, 2021 9:17 am

A thing of beauty!

It will be interesting how to compensate feedback of the supply so that it doesn't oscillate with a load as unruly and non-linear as the fusor.

Great work as always!

JoeBallantyne
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Re: Prototype 180kV Power Supply

Post by JoeBallantyne » Thu Jul 22, 2021 9:24 pm

So running some numbers based on your post (((180,000 / 10) / 1000) * 21) / 1.414 = 267V RMS.

Are you running that beast off a single tap from a 480KV 3 phase line? That would be a nominal RMS voltage of 277V relative to neutral/ground.

I'm just wondering how you are getting your line voltage of ~270V.

Joe.

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Joe Gayo
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Re: Prototype 180kV Power Supply

Post by Joe Gayo » Fri Jul 23, 2021 12:14 am

@Joe

It's a resonant converter, so you get a boost greater than the turns ratio ... and the front end is a PFC boost stage for the DC bus feeding the half-bridge.

@Cai

It's certainly doable. Everyone who uses a Spellman or Glassman supply to run a fusor has experienced this first hand. I plan on using type-III compensation.

Here is my control board (there is a separate board for the Boost Stage and Half-Bridge Inverter)
controller.PNG

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