Time dependent study on a 3D multiturn coil inside of an electrical circuit

Hello,

I am trying to model the voltage in function of time across a 3D multiturn coil inside of an electrical circuit. To do this I use the Magnetic Fields and the Electrical Circuit physics and a Time Dependent Study with a coil current calculation preceding it. In the electrical circuit there is a voltage source generating a pulse . Moreover, I have added in the Magnetic Field study a Gauge Fixing and a multiturn coil with a reference edge (the coil excitation is set to current from circuit and in the electrical circuit there is an External I vs. U). Finally, the initial value of the magnetic vector potential is 0 in x,y and z and there is magnetic insulation on the surfaces of the air box surrounding the coil.

When I try to run the simulation COMSOL 4.3b displays the following error message:


Failed to find consistent initial values.
Segregated group 2

Singular matrix.

For mesh-case 0 there are 113600 void equations (empty rows in matrix) for the variable mod1.mf.psi.
at coordinates: (-0.00949828,-0.0132493,-0.010552), (-0.00882481,-0.0125927,-0.0109472), (-0.00959674,-0.0126878,-0.0111544), (-0.00884992,-0.0132232,-0.0111593), (-0.00894054,-0.0125715,-0.0118075), ...
and similarly for the degrees of freedom (empty columns in matrix).
Last time step is not converged.



Has anyone any idea why this error occurs?

Thanks,

Frédéric