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Dear Sir or Maddam,

i´m trying to investigate the resulting eddy currents in the walls of a rf shielding chamber created by magnetic coils located inside of the chamber, these coils will be excited by current ramps. To do this, i´m using Comsol 5.1 and currently trying to run a 3D simulation since there wouldnt be much rotation symmetry in the later setup to do this by a 2D simulation.
I started the study by setting up everything according to the stationary 3D helmholtz-coil tutorial (-->using the ACDC module) and changing it a little bit. The study only contains one multi-turn coil and two metal plates, embedded in a sphere. The stationary solution worked fine.
So under "components >> definitions" i added a ramp function and named it cr1. Then, in the "multi-turn coil" settings i edited the coil current from "I0" to "I0+(I0*cr1(t[1/s]))". When i try to solve this study, i always get the error message "Failed to find consistent initial values.
Matrix has zero on diagonal.
Last time step is not converged.
- Feature: Time-Dependent Solver 1 (sol3/t1)".

Then i tryed using a single-turn coil and excite the coil again by a ramp function using gap feed, but i get the same error message.

Now i´m kind of clueless how to go on and i guess i need some help since the error message is pretty useless for me.

Thank you guys for any help