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Registered Member #2939
Joined: Fri Jun 25 2010, 04:25AM
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Posts: 615
Ahh, yes I F***ed up a bit there. Go to 'Properties - Conductors'. pick 14k from the drop down box, click 'modify'. change 'prescribed voltage' from 0 to what you want. I thought the result looked a little odd when I ran the sim - should have looked closer .
I'm off home now - wont be back online for about 14 hrs.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
2Spoons wrote ...
Ahh, yes I F***ed up a bit there. Go to 'Properties - Conductors'. pick 14k from the drop down box, click 'modify'. change 'prescribed voltage' from 0 to what you want.
TY! these instructions made it easy.
done: but now i get this error
" Error: Ran out of precision at (8.68677590551, 28.8333033527). I attempted to split a segment to a smaller size than can be accommodated by the finite precision of floating point arithmetic. Try increasing the area criterion and/or reducing the minimum allowable angle so that tiny triangles are not created."
I dont like it when my machines start replying in first person.!!!
Registered Member #1667
Joined: Sat Aug 30 2008, 09:57PM
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Are there any products out there using Hermes2d? just found it looking around for a better FEM solver. You can even have your calculations done remotely.
Registered Member #2939
Joined: Fri Jun 25 2010, 04:25AM
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Posts: 615
Never seen that error before! It might be related to the arcs on the end of the plates - they are made up of line segments. Try redrawing the arcs with fewer segements (arcs have a dialog box where you can spec the min segment size in degrees , default is 5 IIRC)
Registered Member #834
Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644
I recommend a "sanity test" with a situation with known solution before believing in these simulations. Verify if the electric field between the plates is correct, for example (voltage difference/distance). Note the irregular boundaries caused by the triangularization, that are not real and indicate too coarse mesh. And, as already commented, sharp corners result in infinite electric field and incorrect results (but probably correct field far enough from the corners).
Registered Member #1321
Joined: Sat Feb 16 2008, 03:22AM
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I think if you just use off-the-shelf foil without any kind of edge treatment or special processing, you probably end up with various microscopic protrusions and deviations in thickness here and there, etc., that would result in unpredictable field enhancement and cause you to have to operate at drastically reduced voltage or suffer low reliability.
I think you're probably better off folding the foil over, which would cost more in terms of foil, but would give you a much less field enhancement.
Also, I think the usual construction technique for HV energy storage capacitors for example is to put several sections in series, and to limit the voltage across any one section to 10 kv, or something like that.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
jpsmith123 wrote ...
I think if you just use off-the-shelf foil without any kind of edge treatment or special processing, you probably end up with various microscopic protrusions and deviations in thickness here and there, etc., that would result in unpredictable field enhancement and cause you to have to operate at drastically reduced voltage or suffer low reliability.
I think you're probably better off folding the foil over, which would cost more in terms of foil, but would give you a much less field enhancement.
Also, I think the usual construction technique for HV energy storage capacitors for example is to put several sections in series, and to limit the voltage across any one section to 10 kv, or something like that.
The folding edge and limiting voltage are excellent points.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
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Posts: 4992
A pragmatic solution is to determine the breakdown voltage of the dielectric empirically, and then provide sufficient dielectric thickness to withstand (conservatively) triple the maximum peak voltage.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
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Proud Mary wrote ...
A pragmatic solution is to determine the breakdown voltage of the dielectric empirically, and then provide sufficient dielectric thickness to withstand (conservatively) triple the maximum peak voltage.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Patrick wrote ...
Proud Mary wrote ...
A pragmatic solution is to determine the breakdown voltage of the dielectric empirically, and then provide sufficient dielectric thickness to withstand (conservatively) triple the maximum peak voltage.
Yes this is what im going to attempt.
I suppose you might want to consider if any de-rating for temperature might be needed with your chosen dielectric and particular conditions.
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Calculating Field Intensity at Edges of Cap Plates.
