Power Supply

This forum is for specialized infomation important to the construction and safe operation of the high voltage electrical supplies and related circuitry needed for fusor operation.
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Nicolas Krause
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Power Supply

Post by Nicolas Krause »

Since I am currently stuck waiting for some parts in the mail to finish my vacuum sensor and I've tightened all the bolts on my chamber, I've started to look at the power supply for my fusor. I purchased the transformer below a number of years back on eBay. It was labelled as an X-Ray filament transformer and was rated for 90kV according to the seller listing and I believe somewhere between 3-10 mA. I'm confident about the voltage rating but less so about the current rating. Unfortunately the listing has now been purged from eBay and I didn't write down the details. The transformer has no center tap, and two sets of leads. I read 0.3 ohms on the secondary set of leads and 20 ohms on the primary set of leads. The transformer obviously has a different configuration than the standard ones used here. I'm not too worried about whether or not it will be powerful enough to achieve fusion, I'd like to get a bit of practice with high voltage first. Building a basic rectified supply will hopefully do that.
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John Futter
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Re: Power Supply

Post by John Futter »

yep its a filament transformer with 90kV insulation between primary and secondary
ie 110 volts in and 3-5 volts out
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Nicolas Krause
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Re: Power Supply

Post by Nicolas Krause »

Well that'll teach me not to purchase things well before I understand what I'm buying! Thanks for the clarification John
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Rich Feldman
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Re: Power Supply

Post by Rich Feldman »

You could try running it in reverse, as a step-up transformer.
Would be a learning experience about core saturation.
Start with adjustable low-voltage AC, e.g. a 12V lighting transformer fed from a variac.
Get set up to measure current in the primary (low voltage) winding of your XRFT.
Start low and work up.
All models are wrong; some models are useful. -- George Box
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Dennis P Brown
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Re: Power Supply

Post by Dennis P Brown »

Sorry for the incorrect item; that is one really tremendous advantages with joining/posting here. The shear wealth of knowledge is breath taking. I often urge newbie's to post possible equipment buys here first so they get both the items they think they are getting, and what to be aware of relative to possible problems with that specific item.

As for using it in reverse, highly unlikely to be useful as any high voltage source and discovery of the voltage limit is likely via a burned out secondary (orginally the primary - which was insulated for a rather low voltage.) I agree this might be an interesting experiment but if you are building a fusor, not sure it is worth the divergence unless you are bored/looking for a learning experience.
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Bob Reite
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Re: Power Supply

Post by Bob Reite »

Running it "backwards" you would probably hit core saturation before you damage what is now the secondary. My guess is, you would hit saturation at about 150 VAC output.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.
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Nicolas Krause
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Re: Power Supply

Post by Nicolas Krause »

I appreciate the suggestions, but I've hucked the transformer in the trash. I've done the basics of characterizing one in my electrical engineering classes and would rather spend the time working on other aspects of the fusor. I do have one of those broken spellman supplies hanging around so I'll probably use the excellent thread there to try and resuscitate it.
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Richard Hull
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Re: Power Supply

Post by Richard Hull »

Dig that Xformer out of the trash, It might come in handy one day with a fabulous buy on an old machlett HV vacuum tube rectifier. Ya' never know...

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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