Energy Losses in Soft Magnetic Materials Under Symmetric and Asymmetric Induction Waveforms

Magnetic losses under triangular symmetric and asymmetric induction waveforms have been measured over a broad range of frequencies and predicted starting from standard results obtained with sinusoidal induction. Nonoriented Fe-Si and Fe-Co sheets, nanocrystalline Finemet–type ribbons, and Mn-Zn ferrites have been investigated up to f = 1 MHz and duty cycles rang- ing between 0.5 and 0.1. The intrinsic shortcomings of the popular approach to loss calculation of inductive components in power elec- tronics, based on the empirical Steinmetz equation and its numer- ous modified versions, are overcome by generalized application of the statistical theory of losses and the related concept of loss separation. While showing that this concept applies both to ferrites and metallic alloys and extracting the hysteresis (quasi-static), excess, and classical loss components, we relate in a simple way the mag- netic energy losses under symmetric triangular induction (square wave voltage) and sinusoidal induction. The loss behavior under asymmetric triangular induction is retrieved from the symmetric one, by averaging the energy losses pertaining to the two different semiperiods. Good comparison with the experimentally measured energy loss versus frequency behavior is demonstrated in all materials.