Modelling tooth-ripple losses in the solid pole faces of synchronous machines using reversible permeability

In situations where a small AC field is superimposed on a strong DC field, the resulting eddy current loss in any magnetic steel present is influenced not only by the relative permeability corresponding to the operating point on the magnetization curve, but also by the minor hysteresis loop generated at that point, i.e. by the incremental or reversible permeability. This paper describes a method of measuring the latter, and of predicting its approximate variation with applied magnetic field strength. The results are then applied to calculating the tooth ripple loss in a solid steel salient pole