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3D mf excitation in power

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Hi,

I want to impose a desired power Pv (inducted by Joule heating) on a conductive boundary in a 3D model with mf physic. The power on this boundary can be calculated with mf.Qsh [W].
I use an impedance boudary condition for this boundary and I apply also a coupling operator intop1.

The coil is excited a with external current density feature on which, I try to impose the current density depending on the value of intop1(mf.Qsh).
I have add an global ODE + DAE, in which I have created a variable diffP = Pv - intop1(mf.Qsh)

The imposed current density is equal to:
Js=sqrt((Pv-diffP)/r0)/coilsection (maybe wrong expression...)
where r0 is the global electrical resistance (P=r0I^2)

It doesn't work... Comsol can't evalutate diffP, why?

error:
For mesh-case 0 there are 1 void equations (empty rows in matrix) for the variable mod1.diffP.
at coordinates: (0,0,0), ...
In Segregated Step:
Returned solution is not converged.
- Feature: Stationary Solver 1 (sol1/s1)

or in trying different solver configurations:

Failed to find a solution.
Segregated Step 1
System matrix is zero.
In Segregated Step 1:
Returned solution is not converged.

I need help please.

Best regards

Julien


0 Replies Last Post 2015年11月30日 GMT-5 05:31
COMSOL Moderator

Hello Julien Givernaud

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