Prediction and use of impedance matrices for eddy-current problems

Inclusion of both skin and proximity effects in the prediction of impedance matrices in eddy-current problems significantly complicates the prediction of the impedance matrix. In this paper, a technique employing a boundary element method is used to predict these impedance matrices using an additional constant vector potential which is added to the interior of every conductor. This constant vector potential is slightly altered for an axisymmetric problem and allows for the easy prediction of induced voltage in an eddy-current conductor. Perhaps the greatest contribution offered by this paper is in the interpretation of these matrices and in particular, with the negative components comprising the resistance matrix. The phasor diagrams, both for voltage and current as well as magnetic fields, are employed to aid in better understanding the information delivered within the impedance matrix. The explanations are directed specifically toward a three-coil axisymmetric problem. The technique is tested against the measured voltage in a three-phase current fed system.