High voltage

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stamasd
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Re: High voltage

Post by stamasd » 07 Nov 2017, 17:43

Let's discuss the secondary of the final large core EE transformer. I actually have a question (or several) for the collective mind of this board at the end.

Per calculations above I will need 492 turns of 30AWG or heavier wire. I have been shopping around, and high-voltage-rated 30AWG wire is hard to find in appropriate lengths (200m is what I need) not to mention fairly expensive even from the usual Chinese sources. I was able to find some 28AWG wire in 300m lengths that's fairly affordable. The catch is that it's rated for 3000V not 10000 or 20000 as I was hoping. I will come back to that.

Now assuming that I use this wire, based on the number of turns, the physical properties of the wire and the space I have available in the core window, the most reasonable geometry would be to wind it in layers of 41 turns per layer, 12 layers total. 41*12=492.
The voltage in the secondary will be 12000Vrms. That comes to 1000V per layer. That would mean the rated voltage resistence of the wire isn't reached unless you consider the difference of potential across 3 layers deep (e.g. from the 1st layer to the 4th layer). Even when considering the peak voltage of around 19000V you still have to look across 2 layers deep (1st layer to 3rd layer etc).

Would this be safe? What if I use some extra insulation between layers, say some thin polyethylene or silicone film? What if I encase the whole secondary in silicone or epoxy resin?

Also, what if I submerge the transformer in mineral oil as it's usually done with HV transformers? Actually I have some reservations regarding that. The wire insulation is silicone. I don't know if this silicone is resistant to mineral oil, or if its mechanical and/or electrical properties wouldn't be degraded by the oil.

As always I appreciate your opinions.
Real name: Silviu Tamasdan

stamasd
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Re: High voltage

Post by stamasd » 09 Nov 2017, 12:33

Steven, do you mind if I take part of this discussion (my posts only, edited appropriately) and repost on the fusor board? I'm hoping to get some fair critique and more ideas in fixing what I'm doing wrong (of which I'm sure there is plenty).
Real name: Silviu Tamasdan

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Steven Sesselmann
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Re: High voltage

Post by Steven Sesselmann » 09 Nov 2017, 14:02

Silviu,

No problem, this is the right forum for this stuff, I did not reply because your questions are a bit specific for my experience, and maybe for the others too. Not many of our regulars work with high voltage x-ray transformers. I can elevate the post to my fb page, maybe someone there knows.

Steven
Steven Sesselmann | Sydney | Australia | gammaspectacular.com | groundpotential.org | rephopper.com | beejewel.com.au |

stamasd
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Joined: 29 Oct 2017, 02:12
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Re: High voltage

Post by stamasd » 09 Nov 2017, 14:39

That's OK, and the reason why I asked. I realize that it's a very specific niche - but I know a place where people of the same niche congregate. :)
(fusor.net) Maybe I'll get more responses by asking there too. But since I posted here first I wanted to ask for your permission.

BYW I just posted there the results of a little neutron experiment I did tonight, in which I referenced some of your results. Namely the nvth that you determined back in 2015 for the Russian 10B corona tubes.
Real name: Silviu Tamasdan

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