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AC/DC module,Simulating a parallel capacitor(Two Circular discs)
Posted Nov 21, 2013, 1:35 a.m. EST Version 4.3b 0 Replies
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I'm using AC/DC module ---->Electrostatics----------->Stationary study in Comsol.
I have tried simulating parallel plate circular electrodes having diameter 63 mm.I'm trying to see how Capacitance varies with plate separation (d).I have defined a cylindrical outer box of radius 630 mm and height
630 mm in which my parallel plate electrodes are placed.I'm not setting any boundary condition for the outer box .
Problem1:
a) I set the boundary condition on electrode as TERMINAL(6 V) and GROUND. and I varied "d" and i'm able to extract information about Capacitance.
Now the problem is that,for a particular "d" value ,as I change the cylindrical outer box dimensions my capacitance value varies.(Not able to do Convergence check).
I'm looking forward to have a precision upto 6 decimal places in my capacitance.Right now I can achieve a precision upto 2 decimal places .
I tried changing "Relative Tolerance" in the "Solver settings" but i can't find the difference.
I tried setting the outer box potential to nearly zero value but it changes my capacitance.
I tried "Infinite Elements" conditions on outer box hoping that comsol will take the potential at the boundary as zero.But it is taking some different value.,not even near to zero.If i'm not setting the boundary condition to the outer box,then by default comsol is taking 0.2 V at the boundary(This I have evaluated using "Point Evaluation" option in comsol).
b) I set the boundray condition on the electrode as TERMINAL(+3 V) and ELECTRIC POTENTIAL(-3V) and I varied "d" and i'm able to extract information about Capacitance.
But now the "Capacitance" itself takes a different value.Why does this happen? The potential difference between the plates is 6 V in both cases and I was expecting capacitance to be same in both cases.
Can anybody help me to sort out this problem.Eager to hear the response.
Gokul Raj R
Hello Gokul Raj
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