-80kV, 40A switching power supply with resonant transformers

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Andrew Seltzman
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-80kV, 40A switching power supply with resonant transformers

Post by Andrew Seltzman » Sun Aug 25, 2013 8:14 pm

I recently(between 2008 and 2012) built a switching power supply that generates -80kV at 40A, for use with fusion research(for my PHD work, not for my fusor; The power supply is designed to drive a klystron amplifier for a 1MW RF heating and current drive experiment). A smaller version of this system may be useful in driving fusors. I have posted construction photos and reverent documents on my website:

http://www.rtftechnologies.org/emtech/r ... t-smps.htm
SAM_1631a.jpg
Andrew
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kcdodd
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Re: -80kV, 40A switching power supply with resonant transfor

Post by kcdodd » Mon Aug 26, 2013 8:27 am

Wow, that is impressive. Is the reason for this to maintain a controlled constant voltage? As apposed to a pulsed capacitor decay? What powers this thing? (edit: found reference to a capacitor bank driving the igbt's)

Andrew Seltzman
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Re: -80kV, 40A switching power supply with resonant transfor

Post by Andrew Seltzman » Mon Aug 26, 2013 5:04 pm

Yes, it's designed to produce a constant, stable, voltage pulse from a 900v electrolytic capacitor bank without any voltage droop as the bank discharges.
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Carl Willis
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Re: -80kV, 40A switching power supply with resonant transfor

Post by Carl Willis » Mon Aug 26, 2013 7:44 pm

Hi Andrew,

Nice work, and and it looks like a fun project as well. I think your paper has a lot of suggestions and calculations that are relevant to high-frequency fusor supplies, and I'll definitely mark it as a top-flight reference for future projects.

-Carl
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Richard Hester
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Re: -80kV, 40A switching power supply with resonant transfor

Post by Richard Hester » Mon Aug 26, 2013 10:09 pm

Yee-haw! The supply looks modest enough in the first picture, until in subsequent views you back up a bit and see it in perspective - a monster. I design switchers for a living, but in this case I'm happy to use someone else's supply so as not to spend a big portion of my time tinkering with the blasted thing.

As a data point, Scott Little recorded dectable neutron activity back in the very early day of the forum with a little Pastic Capacitors -style 20kV power pack (20 kV, 10 mA if I remember correctly). He got about 10k neutrons/sec. I think he was the second neutron club member, very close on the heels of Richard Hull.

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Richard Hull
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Re: -80kV, 40A switching power supply with resonant transfor

Post by Richard Hull » Tue Aug 27, 2013 9:05 pm

Andrew, Carl is right. Your references and supplied data are useful and are just the kind of feedstock needed for the electronics buff looking to roll his own modern supply. Thanks for the valuable addition to this forum.

Scott Little and I sort of built our systems in parallel. I beat him by only two weeks, If I remember correctly.

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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Re: -80kV, 40A switching power supply with resonant transfor

Post by Richard Hester » Sun Sep 01, 2013 12:41 am

What I remember from the time was that he got results fairly quickly from something thrown together from materials on hand, also the relatively small amount of fiddling involved. I definitely want to try a neon XFMR inductive ballast for my first foray - sounds like a possible solution for keeping a stubborn plasma lit up.

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