60 kV feedthrough design?

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Connor Givans
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60 kV feedthrough design?

Post by Connor Givans »

Good day everyone,
I wish to build a cooled fusor (as I would like to run higher-than-average currents for experimental purposes and lower chances of a grid melt into my turbo), and would need to build my own 60kV feedthrough and flange plate with the two flourinert lines running through it. I am thinking of building the grid itself out of stainless steel capillary tubing and forcing the flourinert through with some pressure, heat-exchanging in a water bath, and entering into a reservoir to resume cycling. I simply am unsure how to fabricate a flange plate that could support a feedthrough of that size, how to prevent flashover and corona discharge, and the best way to run the coolant lines alongside it.
Thank you all for your time,
Connor.
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Liam David
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Re: 60 kV feedthrough design?

Post by Liam David »

Andrew Seltzman built a fluorinert cooled grid for his fusor.
http://www.rtftechnologies.org/physics/ ... d-grid.htm
Connor Givans
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Re: 60 kV feedthrough design?

Post by Connor Givans »

I am more curious as to specific details in the size for a 60kV feedthrough, to prevent flashovers and other issues. I have looked over that page several times before, and I quite like the build quality and design, but lack a shop to work in for now, when I get the money and parts together I'll head somewhere. First and foremost I'd like to get some CAD drawn up, however - ergo my curiosity towards the best size for one. I also wonder if there is anything else I should worry about when dealing with homemade feedthroughs?
Connor
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Adam Szendrey
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Re: 60 kV feedthrough design?

Post by Adam Szendrey »

Generally (when using a good insulator as a standoff) you can start from the breakdown voltage of air at certain conditions (temperature, humidity, pressure). But I'd say simply look at feedthrough designs with a 60 kV rating, on the market and base your dimensions on those maybe. KJL, for example, sells 60 kV feedthroughs:

http://www.lesker.com/newweb/feedthroug ... id=20kv_cf

It seems if you register you can even download cad drawings/models.
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Richard Hull
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Re: 60 kV feedthrough design?

Post by Richard Hull »

$1260.00 for a 60kv insulator is steep, but all pro stuff rated to do the job in vacuo is expensive. All the best to anyone trying to cobble something up to do this job from scratch.

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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Andrew Robinson
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Re: 60 kV feedthrough design?

Post by Andrew Robinson »

As always, do some outside research. Read up on the IEEE, IEC, NEMA and ANSI Standards for high voltage standoff and feed through insulators. That will introduce you to some of the necessary concepts, electrical properties, and differences. Look up BIL ratings too.
I can wire anything directly into anything! I'm the professor!
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Adam Szendrey
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Re: 60 kV feedthrough design?

Post by Adam Szendrey »

Richard, I was actually looking at buying a 30 kV feedthrough earlier (it costs around 200 dollars) , and I did notice that if you double the voltage rating you end up having to pay almost 6 times as much! I do wonder if this really is justified, but then again I don't design HV feedthroughs.
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Richard Hull
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Re: 60 kV feedthrough design?

Post by Richard Hull »

HV feedthroughs are all overdesigned in the professional arena. Vacuum rated HV feedthroughs are no exception and this speaks to their pricing.

Proper field control can see a 30kv insulator used for 40kv or even more. Few know how to utilize field control. They just want to connect a wire and walk away. They are forced to pay the high prices for this luxury. In most all professional setups, all insulators must meet a spec for the voltage applied and the manufacturers must warrant this against stupidity for safety sake. Again, this supports the high pricing.

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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Rich Feldman
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Re: 60 kV feedthrough design?

Post by Rich Feldman »

Adam Szendrey wrote:... I did notice that if you double the voltage rating you end up having to pay almost 6 times as much! ...
Empirical formulas have served engineers and scientists for millennia.
In the catalog page Adam pointed to, dimension D (in inches) is well represented by
1.0 + 0.1 * VR (in kV).

The price, without considering style differences, is around
$86 + $0.32 * VR squared, or $202 + $0.0048 * VR cubed. :-)
kjl_fdt.PNG
kjl_fdt.PNG (13.66 KiB) Viewed 9162 times
Those coefficients are all from fitting functions in Excel, but I doubled the weighting of the only 30-kV product, and halved the weighting of three high-priced 25-kV products (and the 60 kV, which is inherently over-represented).
All models are wrong; some models are useful. -- George Box
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Re: 60 kV feedthrough design?

Post by derekm »

So the voltage is the square root of the depth of pocket :)
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