
Problem Type:
A plane problem of AC magnetic field.
Geometry:
Two copper square crosssection conductors with equal but opposite currents are contained inside rectangular ferromagnetic coating. All dimensions are in millimeters.
Given:
Magnetic permeability of air μ = 1;
Magnetic permeability of copper μ = 1;
Conductivity of copper σ = 56,000,000 S/m;
Magnetic permeability of coating μ = 100;
Conductivity of coating σ = 10,000,000 S/m;
Current in the conductors I = 1 A;
Frequency f = 100 Hz.
Problem:
Determine current distribution within the conductors and the coating, complex impedance of the line, and power losses in the coating.
Solution:
We assume that the flux is contained within the coating, so we can put a Dirichlet boundary condition on the outer surface of the coating. See HMagn2.pbm problem in the Examples folder for the complete model.
The complex impedance per unit length of the line can be obtained from the equation Z = ( V_{2}  V_{1} ) / I
where V_{1} and V_{2} are voltage drops per unit length in each conductor. These voltage drops are equal with opposite signs due to the symmetry of the model. To obtain a voltage drop, switch to Local Values mode in postprocessing window, and then pick an arbitrary point within a conductor.
The impedance of the line Z = 0.000484 + i 0.000736 Ohm/m.
To obtain power losses in the coating:
In the postprocessing mode, choose Pick Elements and pick the coating block to create the contour.
Choose Integral Values and select Joule heat from the list of integral quantities and choose Calculate.
The power losses in the coating P = 0.0000427 W/m.
See the HMagn2.pbm problem in the Examples folder.