Approximate treatment of nonlinear eddy current problems

This work presents a new systematic approach for the computation of the fundamental frequency eddy current losses in a magnetic material. It is based on the use of the time averaged value of the permeability over a complete cycle. This depends on the magnetization characteristics of the material and the time variation of the source. Curves depicting the dependence of this weighted permeability (complex in the presence of hysteresis) on the magnetic field are given for different magnetic materials. The practical application of this concept for the solution of eddy current problems is demonstrated for one dimensional multilayer problems. A combination of the micro circuit and transfer function representations is used, with the former restricted to the nonlinear layers. An iterative procedure, in which a continuously increasing part of the magnetic material is represented by its equivalent circuit, has been developed. Numerical results are presented for cylindrical geometries and are compared with those obtained by experiment, time domain analysis, and using a value of μ corresponding to a given value of H.