xray transformer questions

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Steven Haid
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xray transformer questions

Post by Steven Haid » Mon Aug 22, 2016 12:35 pm

I am starting work on replacing the NST with an Xray transformer in my power supply.

My xray transformer has 3 wires coming out of the secondary. I was expecting that one of the wires was a center tap, but when measuring the resistance I found that the wire labeled GND does not seem to be connected to any of the other wires or to the magnetic core. Perhaps this wire is supposed to be a centertap but is broken, any other ideas?

I had thought that an x-ray transformer for use in a fusor must have a center tap secondary, because the center tap has no voltage, and can therefore be attached to ground. I am now beginning to understand that a center tap is not required, and that one end of the secondary can be attached to ground. This post viewtopic.php?f=11&t=10837 from Dennis was helpful as his transformer did not have a center tap.

Please see attached proposed schematic and picture of the x-ray transformer.
My fusor will be attached to the house ground.

I have a few questions:

(1) Regarding the schematic - I would appreciate confirmation that I'm not doing something wrong.

(2) My transformer is smaller than others I've seen discussed in these forums. Is there a way to estimate it's maximum current.

(3) Do these transformers often burn out when running a fusor?
Attachments
xray_transformer.jpg
xray transformer
power_supply_schematic.jpg
power supply schematic

Jake Wells
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Re: xray transformer questions

Post by Jake Wells » Mon Aug 22, 2016 5:34 pm

That is NOT an x Ray transformer. It's a low power filament transformer for the filament of the x Ray tube. They only have an output of around 4-8v
“The day science begins to study non-physical phenomena, it will make more progress in one decade than in all the previous centuries of its existence.”
― Nikola Tesla

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Steven Haid
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Re: xray transformer questions

Post by Steven Haid » Tue Aug 23, 2016 2:36 pm

Thanks for clearing that up. I did some reading on how these x-ray machines work, I wish I had done that before.

An X-ray machine has a main HV transformer, the output is converted to DC and applied to a cathode and anode target. The cathode needs to be heated so that it can release electrons, the filament transformer provides the heater current. The filament transformer secondary is exposed to the DC HV that is on the cathode, so the filament transformer needs to provide isolation so that this DC HV doesn't short out to the primary of the filament transformer.

So, I'm back to the drawing board. Any comments would be appreciated.

- I saw a post where someone removed a NST from it's case. The reason for removing it is to disconnect the secondary centertap from the case. Then a full wave rectifier is used. This doubles the output voltage as compared to using the centertap. Also, somebody said they ran their NST setting the input voltage to 150 VAC from the VARIAC. It was also mentioned that X-rays were generated, I suppose that lead sheet could shield the x-rays. Where do these x-rays come from? The peak voltage generated for this should be 26KV (15KV x 1.41 x (150/120), unless I made a mistake. This assumes using 150 vac for the primary doesn't burn out the NST. It seems that this might be enough voltage to begin to generate fusion.

- Also I am considering boosting the output voltage from the NST with a home made transformer. I'll need to do some research to understand how to do this.
I think if this approach is used the NST would not have to be removed from it's case.

- Glassman makes DC HV supplies but they are expensive at the voltage and current needed for a fusor.

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Richard Hull
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Re: xray transformer questions

Post by Richard Hull » Tue Aug 23, 2016 6:00 pm

Read the FAQ on the valueless nature of the neon sign transformers for fusion. You still need to do a lot of reading in the FAQs. They are not only there to guide you, but to keep you from costly errors and very bad assumptions like you make above based on your limited knowledge of the actual nature of the neon sign transformer and its application for which it was originally designed.

You might try the highly visible FAQ #7 It was oddly named "neon transformers - the facts" in this forum's FAQs pile on the first page!

viewtopic.php?f=29&t=10333

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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