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• Broadband investigation (1 Hz-10kHz) on the loss properties and domain dynamics on HGO Fe-Si. Role of the sheet thickness (conventional 0.29 mm vs. novel 0.18 mm thick laminations). • Fluxmetric measurements of hysteresis loops and losses are associated with dynamic high-speed Kerr imaging of the domain structure. • Modeling of loss versus frequency made by keeping into account deep skin effect. • The dynamic response of the array of 180° dws is treated starting from the concept of dw bowing. The dw configuration along the magnetization cycle and its evolution with frequency are obtained by numerical modeling. The magnetic properties of high-permeability grain-oriented (HGO) Fe-Si sheets have been investigated in the frequency range 1 Hz-10 kHz, with attention devoted to the role of thickness on the behavior of the magnetic losses and the phenomenology of skin effect. The study is focused on the wideband response of 0.174 mm and 0.289 mm thick sheets, comparatively tested at peak polarization values ranging between 0.25 T and 1.7 T. The experiments associate fluxmetric measurements with direct Kerr observations of the dynamics of the domain walls. A picture of the magnetization process comes to light, where the dynamics of the flux reversal takes hold under increasing frequencies through the motion of increasingly bowed 180° walls, eventually merging at the sheet surface for a fraction of the semi-period. This effect can be consistently predicted, starting from the Kerr-based knowledge of the equilibrium wall spacing, by the numerical modeling of the motion of an extended array of 180° domain walls, subjected to the balanced action of the applied and eddy current fields, and the elastic reaction of the bowed walls. This model can be incorporated into the general concept of loss separation, by calculating the classical loss component through the solution of the Maxwell's diffusion equation under a magnetic constitutive law identified with the normal DC curve. The numerical domain wall model and the loss decomposition consistently predict that the excess loss component, playing a major role in these grain-oriented materials at power frequencies, tends to disappear in the upper induction-frequency corner. [ABSTRACT FROM AUTHOR]

Abstract: We propose a simplified dynamic hysteresis model for the prediction of magnetization behavior of electrical steel up to high frequencies, taking into account the skin effect. This model has the advantage of predicting the hysteresis loop and loss behavior versus frequency with the same accuracy provided by the Dynamic Preisach Model with a largely reduced computational burden. It is here compared to experimental results obtained in Fe-Si laminations under sinusoidal flux up to 2kHz. [Copyright &y& Elsevier]

• New manufacturing procedures can produce optimized non-oriented electrical steels. • Samples of non-oriented 3% silicon steel were submitted to a 2.5% thickness reduction and heat treated. • Under increasing frequencies, the energy loss of the deformed and recovered samples becomes lower. There is increasing interest in the optimization of non-oriented electrical steels for applications under excitation frequencies above 400 Hz. We discuss in this paper the possibility of a new manufacturing procedure, where skin-pass and subsequent heat treatment for recovery are applied as the two last stages of sheet processing. Samples from a commercial non-oriented 3 wt% silicon steel were submitted to 2.5% thickness reduction and were heat treated at temperatures ranging between 600 and 850 °C for 2 h. It is shown that, although the hysteresis loss increases with plastic deformation, the excess loss decreases in such a way that under increasing magnetizing frequencies the total energy loss of the deformed and recovered sample becomes lower than in the starting material. The higher the annealing temperature the lower the frequency at which crossover of the loss curves is observed, as long as full recrystallization does not occur. It is assumed that with the dislocation structures left in the deformed and partially recovered samples one achieves a condition of increased fragmentation of the magnetization process, that is, of increased number of concurring correlation regions (Magnetic Objects). The corresponding decrease of the excess loss component can eventually overcompensate the deterioration of the quasi-static magnetic properties, leading to lower total losses. [ABSTRACT FROM AUTHOR]