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Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
2Spoons wrote ...
Ran the sim - peak E field is ~2e9 volts/m. Did I get your units wrong in the dxf? I used mm. Switched to inches and got a field peak of 9e7 V/m.
I always use inches.
2Spoons wrote ...
And here's a pretty picture. The mesh should probably be finer for a better result.
i left one side radiused, and the other at a right angle to see the difference in field intensity.
UPDATE:
pics Voltage plot. (right side has rounded edges) Upper magenta is 14kV, lower cyan is 0 volts, midpoint of gap is yellow 7 kV as would be expected.
Field density plot, V/m. Left side, right angled edges W/ equipotential lines.
Density plot, Rounded edges, without equipotential lines.
Density plot, Rounded edges, with equipotential lines.
Round edges, Density plot, zoomed in.
Square left end, voltage plot.
Horizontal top plate should be 14kV, lower plate 0V, two circles at right and left should be 7kV, DXF is in inches. I cant figure out how to work this dam software! ]platefemm.zip[/file]( DXF file for FEMM4.2)(newest)
Registered Member #1321
Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843
I think if you have a perfectly square edge, you'll have a singularity - meaning that the more refined your mesh is, in the vicinity of the edge, the higher the field will be.
Registered Member #2939
Joined: Fri Jun 25 2010, 04:25AM
Location:
Posts: 615
Because I'm feeling generous, and because this is way more interesting than generating part numbers for work, here is your dxf turned into a FEMM file ready to simulate. I've found you can define the insides of the conductors as <no mesh>, which saves a bit of compute time. I've added a 7000V conductor (Properties menu- Conductors - Add) and assigned it to the two 'resistor bodies'. (choose 'arcs' button , right click next to the arc of interest, click properties button - the box with a hand on it - select "7k" from the drop down box labelled "in conductor"). I've also refined the mesh in some places by unchecking " choose mesh automatically" and changing the value in the "local segment size " box.
Persevere, look at what I've done, and you'll get the hang of this rather powerful bit of freeware. ]cplates2.zip[/file]
Registered Member #1792
Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527
FlexPDE has a student version, I used it a while ago in a class.
I haven't used it in quite a while but as I recall the help files had some tutorials and example problems in EM simulation which will get you to simulating a capacitor pretty easily.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
2Spoons wrote ...
Because I'm feeling generous, and because this is way more interesting than generating part numbers for work, here is your dxf turned into a FEMM file ready to simulate. I've found you can define the insides of the conductors as <no mesh>, which saves a bit of compute time. I've added a 7000V conductor (Properties menu- Conductors - Add) and assigned it to the two 'resistor bodies'. (choose 'arcs' button , right click next to the arc of interest, click properties button - the box with a hand on it - select "7k" from the drop down box labelled "in conductor"). I've also refined the mesh in some places by unchecking " choose mesh automatically" and changing the value in the "local segment size " box.
Persevere, look at what I've done, and you'll get the hang of this rather powerful bit of freeware.
TY, i really needed you to list the steps i need to do something useful so thanks youve helped a lot.
Im trying to change the upper horizontal plate to 14kV, right now there both at 0 volts!
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Calculating Field Intensity at Edges of Cap Plates.
