Characterization and Prediction of Magnetic Losses in Soft Magnetic Composites Under Distorted Induction Waveform

A general approach to magnetic losses in soft magnetic composites (SMC) is discussed. It is applied to exciting conditions typical of applications, where the induction waveform is most frequently nonsinusoidal. The standard predicting approach, based on the statistical theory of losses (STL) and the related concept of loss separation, is extended to the case of granular heterogeneous materials. As a starting point, the classical loss component is calculated, taking into account that in small enough samples the measured loss is independent of the specimen cross-sectional area, because of negligible grain-to-grain (macroscopic) eddy currents. The loss separation is then performed under the conventional sinusoidal induction regime and the STL is used to identify a limited set of parameters, associated with the prediction of the excess loss, by which the energy loss under distorted induction can be predicted. Significant predicting examples are provided, regarding two different SMCs, where the induction waveform is either triangular or distorted by introduction of a third harmonic component.