Capacitance of a Coil

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TobyA
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Capacitance of a Coil

Post by TobyA »

Hello,

I am trying to simulate the capacitance of a coil. Specifically I want to calculate the capacitance between the windings of the coil.
As it seems I have several options to do this. The fist option would be to cut up the geometry, and simulate just the capacitance of a single winding.
With this method however I won't be able to solve unregular coil shapes. Also I would ignore a large portion of the fringe fields.

The second method would be to solve the coil as a complete geometry. This is the way I am currently trying to go.
I've already simulated the electric field of a test geometry, by coupling the Static current solver, and the electrostatic solver.
Coil_E-Field.png
(550.47 KiB) Not downloaded yet
This is the sif file for this case:
case_WK.sif
(4.14 KiB) Downloaded 345 times
Now at this point I don't know how to continue. My first Idea would be to solve the capacitance matrix, and assign the surface of the coil as the capacitance body.
I've tried this and received the following error:

Program received signal SIGSEGV: Segmentation fault - invalid memory reference.

Backtrace for this error:
#0 ffffffffffffffff

I think this might have something to do with the Variable I've assigned to the boundary condition in question.

How can I calculate the capacitance matrix for this case? Or ist there a fundamentally better solution to this problem?

Thank you!
raback
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Re: Capacitance of a Coil

Post by raback »

Hi

Nice picture!

Capacitance between i and j are is defined such that Q=C_ij(U_i-U_j), for example. In your picture you don't have the system in single potential. Hence the potential matrix might not be directly applicable to this as it automates the permutation of unity potential and uses those to compute the capacitance matrix.

If you just have a binary system you can use the energy of the electrostatic field to compute the capacitance. But for a capacitance matrix among N bodes you need to compute the induced charges for each body in N configurations to obtain sufficient amount of data to determine the matrix.

-Peter
TobyA
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Joined: 31 Jul 2018, 16:40
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Re: Capacitance of a Coil

Post by TobyA »

Hi,

thank you for the explanation!
Based on this, I think I will calculate the capacitance from the energy of the e-field.

The solver log also shows a capacitance value:

StatElecSolve: Tot. Electric Energy : 1.3217299626738402E-012
StatElecSolve: Capacitance : 2.7699787741689149E-012
StatElecSolve: Result Norm : 0.56917218205210851
StatElecSolve: Relative Change : 3.3777045981497629E-010

Does this value represent the total capacitance of the charged surfaces?
raback
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Re: Capacitance of a Coil

Post by raback »

Yes, it is the capacitance computed directly from the energy assuming voltage difference given by the min and max potential at the boundary. -Peter
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