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Registered Member #3324
Joined: Sun Oct 17 2010, 06:57PM
Location:
Posts: 1276
hen918 wrote ...
I think the coil formers I bought from RS were made of some sort of thermosetting plastic although they did cost a fair bit and they're much smaller than the ones you need...
Exactly. Saddly when it gets to this size it has to be all custom.... :/
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Big nylon washers can be handy for splitting HF chokes into sections, though I'm not sure how you could apply it here. You can alternate small and large nylon washers to make a really good split bobbin.
Registered Member #3324
Joined: Sun Oct 17 2010, 06:57PM
Location:
Posts: 1276
Proud Mary wrote ...
Big nylon washers can be handy for splitting HF chokes into sections, though I'm not sure how you could apply it here. You can alternate small and large nylon washers to make a really good split bobbin.
Thats a rather interesting idea... but i think machining it would be better however as there are no gaps that the electricity can track through.
I think that new core design should easily be able to handle 20... even 30kV maybe across each bobbin really. What does everyone else think? the last image will work for a coilform?
From then on i would just need to work out the mounting...
I guess its very much a risk and tradeoff between Budget, reliability and risk of faliure
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
i would do at least a simple FEMM estimate on field intensity, as JPsmith123 and i went to great lengths to get things right, and still had occasional blow outs of our precioussssss ( Gollum reference implied).
my high voltage Probes and this current transformer im making are worth getting right, and im sure JP feels the same.
Thomas W wrote ...
I guess its very much a risk and tradeoff between Budget, reliability and risk of faliure
Registered Member #3324
Joined: Sun Oct 17 2010, 06:57PM
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Posts: 1276
Patrick wrote ...
i would do at least a simple FEMM estimate on field intensity, as JPsmith123 and i went to great lengths to get things right, and still had occasional blow outs of our precioussssss ( Gollum reference implied).
my high voltage Probes and this current transformer im making are worth getting right, and im sure JP feels the same.
Hmm, i don't quite understand why i need to do the FEMM? I also have no clue how to use the software, it seems rather complex and i don't think i would understand what to do with any data i would get back.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
hv probe link
Ok new construction and assembly is about to begin, so we will see if my probes work or not shortly.
Based on my own research and experiments, Ross Engineerng, Northstar, Tektronics, Caddock and Marco Denicolai's work ive come up with this as the basic building block:
The resistor's V drop is linearized with the cap plates, and grading rings.
Marco Denicolai's explanation of his 20 liter water HV probe (600kV). [Note what i have highlighted in green.] His PDF is here:
Marco's tesla and thesis site:
This pics show color gradients and locations that might initiate arcs at which point were all screwed.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
thats alright distance collaboration is a sloppy blur...
in any case, your skills drafting seem good enough, just export as a DXF to FEMM 4.2 (free) as a (2-D dxf) then click metal for HV, metal for ground, and some other stuff, then click field or gradient. the help file and i could probly get every thing you need, its just limited to 2D DXF, so you need a cross section, i think vertical in your case through the ferrite.
this FEMM is easy and well worth learning as it freed me up to widen some dimensions and avoid failures of these valued projects.
or, easier, (almost as good) just be sure to avoid sharp corners and make-up a non-ideal rule for V/mil insulation, which your design wont violate.
EDIT: in your previous pics, are the cyinders grounded at the botttom, and anti-phased at the top? and what the freq, since your using PVC? you might want to survey my bio-oil thread too.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Thomas W wrote ...
Okey, i've had a little fun with FEMM, simulating the one with many taps: Under Oil:
In Air
No difference?
yes, theres no difference in field gradient (very little), but the insulating value is much graeter for oil than air. so you can see (as I suspected) your upper ends are anti-phased and that's where the breakdown from tracking-to-core-to-tracking will occur. those pictures pretty much tell you the overvoltage and frequency derated limitations.
what are the teal and magenta color voltages? is this center tap grounded? (are you still figuring for +14-0-14 ?) and whats the inch distance between the metal magenta and metal teal locations in a straight line? and remember the closer the lines are, the more willing the air is to break.
as you said in a PM, if you can get transformer oil vacuum de-gassed, thats ideal !
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HVHF Bobbins
