History effect in inhomogeneous superconductors

A model was proposed to account for a new kind of history effect in the transport measurement of a sample with inhomogeneous flux pinning coupled with flux creep. The inhomogeneity of flux pinning was described in terms of alternating weak pinning (lower jc) and strong pinning region (higher jc). The flux creep was characterized by logarithmic barrier. Based on this model, we numerically observed the same clockwise V-I loops as reported in references. Moreover, we predicted behaviors of the V-I loop at different sweeping rates of applied current dI/dt or magnetic fields Ba, etc. Electric transport measurement was performed in Ag-sheathed Bi2-xPbxSr2Ca2Cu3Oy tapes immersed in liquid nitrogen with and without magnetic fields. V-I loop at certain dI/dt and Ba was observed. It is found that the area of the loop is more sensitive to dI/dt than to Ba, which is in agreement well with our numerical results.Comment: To appear in Phys Rev B, October 1 Issu

New nanocrystalline materials for power electronics applications

New nanocrystalline materials for the applications in the power electronics systems are developed and tested. These materials are intended to be used in the magnetic circuits of switching-mode power supplies (SMPS). The aim was to achieve extremely low hysteresis and non-linearity in operating region resulting in increased efficiency and decreased weight and size whilst keeping low price of the high-power frequency converters for SMPS

Modelling of complex permeability in cores

In the numerical field analysis a problem that still remains is the development of magnetic parameter models that accurately represents the effect of magnetic anisotropy under complex magnetic conditions. Two modified approaches have been used for the calculation of complex permeability in oriented FeSi lamination. In the first approach pure relaxation processes have been accepted in model approximation and the hysteresis effects have been taken into account separately neglecting the relaxation. In the second approach, besides separated pure irreversible processes also mixed processes, i.e. relaxation and hysteresis mutually influenced are considered. In weak alternating field these irreversible processes have been represented by Rayleigh loop