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Alternating current (ac) losses in conductor-on-rounded-core (CORC) cables of YBCO high-temperature superconducting (HTS) tapes are a significant challenge in HTS power applications. This study employs two finite element analysis (FEA) models to investigate the contributions from different ac loss components and provide approaches for reducing ac losses in cables. An FEA model based on the T-A formulation treats the cross section of thin superconducting layers as 1D lines and, therefore, only can predict the ac loss generated by the perpendicular magnetic field. In contrast, the model based on H-formulation can be performed on the actual 2D rectangular cross section HTS tapes to provide the total ac losses generated by magnetic fluxes penetrating from both the edges and surfaces of HTS tapes, although this model requires more computing time and memory. The 1D and 2D simulation models were validated by cross comparing the results from both models and by comparing sub-section and full cross section models. Subsequently, two models relate cable design and operational parameters to the surface and edge losses of a two-layer CORC cable by considering the (1) relative contributions of edge and surface losses to the overall ac losses; (2) effect of the current distribution between inner and outer HTS layers on ac losses; (3) impact of the tape alignment on ac losses in each HTS layer; (4) influence of the thickness of HTS layers on ac losses; (5) effect of size and number of inter-tape gaps on ac losses; and (6) contribution frequency on the ac losses. The research results given in this paper are therefore not only valuable to suggest strategies for reducing ac loss in multi-layer cables but also for developing more accurate and effective methods to calculate ac loss in CORC HTS cables. [ABSTRACT FROM AUTHOR]

La(Fe,Si)13-based compounds are considered to be very promising magnetocaloric materials for magnetic refrigeration applications. Many studies have focused on this material family but only in bulk form. In this paper, we report the fabrication of thick films of La(Fe,Si)13, both with and without post-hydriding. These films exhibit magnetic and structural properties comparable to those of bulk materials. We also observe that the ferromagnetic phase transition has a negative thermal hysteresis, a phenomenon not previously found in this material but which may have its origins in the availability of a strain energy reservoir, as in the cases of other materials in which negative thermal hysteresis has been found. Here, it appears that the substrate acts to store strain energy. Our exploratory study demonstrates the viability of thick films of the La(Fe,Si)13 phase and motivates further work in the area, while showing that additional perspectives can be gained from reducing the dimensionality of magnetocaloric materials in which the magneto-volume effect is large. [ABSTRACT FROM AUTHOR]

A numerical model is developed for calculating the total alternating-current (ac) loss of Cu-stabilized Y[Ba.sub.2][Cu.sub.3][O.sub.7-[delta]] (YBCO) coated conductors with a ferromagnetic substrate. The model has addressed the other aspects of YBCO conductors, including the field dependence of the critical current density and n value and nonuniformities in the conductor.

This paper presents a study of the total ac loss characteristics of a rolling-assisted biaxially textured substrate (RABiTS) YBa2Cu3O7 (YBCO) sample exposed to a parallel ac magnetic field. The results have shown that, for a given applied magnetic field and transport current, a RABiTS YBCO tape can generate very different magnitudes of ac loss, depending on whether the transport current and applied field have the same phase or opposite phase. The results of this study are very important for the optimization of the design of a RABiTS YBCO cable because they can suggest an appropriate arrangement of RABiTS tapes in a cable to minimize the cable ac loss. In this study, both experimental and finite-element method simulation approaches were employed. A modeling model that takes the magnetic field dependent permeability and ferromagnetic loss of the substrate into account reproduced well the experimental data for both self-field and total ac losses. [ABSTRACT FROM AUTHOR]

In this paper we present a finite element model using the commercial COMSOL® software package for calculating the ac loss in bifilar stacks of high temperature superconducting tape. In the model, the current-voltage relationship characterizing the superconducting properties is assumed to follow a power law. The calculations were performed for infinite bifilar stacks with different values of layer-to-layer separation D. With appropriate settings for the boundary conditions, the numerical results agree well with the analytical data obtained from a recently proposed model [J. R. Clem, Phys. Rev. B 77, 134506 (2008)]. The numerical approach was also used to investigate the end effects in a bifilar stack to answer the following question: how many layers away from the end of a stack are required before the environment of a given layer is identical to that in an infinite stack? We find that the answer to this question depends strongly on the value of D. Based on this study, a model for calculating the ac loss in bifilar noninductively wound coils with a finite number of turns is proposed. [ABSTRACT FROM AUTHOR]

A numerical model is developed to calculate the total alternating-current (ac) loss of Cu-stabilized YBa2Cu3O7-δ (YBCO) coated conductors with a ferromagnetic substrate when carrying an alternating transport current in an ac background magnetic field. The time evolutions of current and magnetic field distributions along the width of the conductor are calculated by solving the one-dimensional Poisson equation for the magnetic vector potential. In addition to the ac loss dissipated in the superconducting layer, the ferromagnetic loss in the substrate and eddy current loss in the Cu stabilizer are also modeled. In the calculations, the superconducting voltage-current behavior is assumed to follow a power law. The model is capable of addressing other practical aspects of YBCO conductors, including the field dependence of the critical current density, and n value, and nonuniformities in the conductor. The magnetic shielding of the ferromagnetic substrate, however, was ignored in the calculations. Numerical results are compared with analytical and experimental results for some special cases. [ABSTRACT FROM AUTHOR]

The total ac loss characteristics of a rolling-assisted biaxially textured substrate (RABiTS) Y[Ba.sub.2][Cu.sub.3][O.sub.7] (YBCO) sample exposed to a parallel ac magnetic field is studied. The results have shown that a RABiTS YBCO tape has generated very different magnitudes of ac loss, depending on whether the transport current and applied fields have the same phase or opposite phase.