General properties of low-frequency power losses in Fe-based nanocrystalline soft magnetic alloys

The dependences sf the power loss per cycle on frequency f and amplitude fl ux density B-m have been investigated for the three main original magnetic states in five sorts of Fe-based nanocrystalline soft magnetic alloys in th e ranges of 10 Hz less than or equal to f less than or equal to 1000 Hz and 0.4 T less than or equal to B-m less than or equal to 1.0 T. The total los s P is decomposed into the sum of the hysteresis loss P-hyst, the classical eddy current loss P-el and the excess loss P-exc. P-hyst has been found to be proportional to B-m(2) and f. The behavior of P-exc/f vs f being equiva lent to P/f vs f clearly exhibits nonlinearity in the range not more than a bout 120 Hz, whereas the behavior of P/f vb f roughly shows linearity in th e range far above 100 Hz and not more than 1000 Hz. In the range up to 1000 Hz, P-hyst is dominant in the original high permeability state and the sta te of low residual flux density, whereas P-exc, in the state of high residu al flux density is dominant in the wider range above about 100 Hz. The fram ework of the statistical theory of power loss has been used for representin g the behavior of P-exc/f vs f. It has been found that the number n, of the simultaneously active "Magnetic Objects" linearly varies as n = n(0) + H-e xc/H-0 as a function of the dynamic field H-exc in the range below about 12 0 Hz, whereas n approximately follows a law of the form n = n(0) + (H-exc/H -0)(m) with 1 < m < 2 in the range far above 100 Hz and not more than 1000 Hz. The values of the field Ho in principle related to the microstructure a nd the domain structure have been calculated for the three states.