An evaluation of loss models for nonlinear eddy current problems

Three method of estimating the eddy current loss in ferromagnetic materials are evaluated. The comparison is undertaken for the simple one dimensional case of a conducting cylinder in a uniform, axially directed, time harmonic field. Three material types, ranging from cast iron to hot rolled steel, are considered at excitation levels of up to 120 kA/m and frequencies of 60, 400 and 1000 Hz. It is shown that despite the occurrence of highly distorted flux density and current density waveforms, a simple time harmonic solution to the eddy current problem provides a very cost effective and reliable estimate of the total and distributed losses. The time harmonic losses are compared with estimates provided by a separating surface model and by a time domain solution for the distorted waveforms.