Effect of the geometry of HTS on AC loss by using finite element method simulation with B-dependent E-J power law

Mono and multifilamentary HTS tapes exhibit non-negligible AC loss in self-field and considerably higher losses in the presence of external magnetic field. The effect of the conductor’s geometry on the AC loss has been investigated in this paper. The nonlinear electromagnetic properties of the superconducting material are expressed with a B-dependent E-J power law and are implemented in Finite Element Method commercial software. The critical current density and the power index n dependence on B are obtained from DC measurements of a real Bi-2223 tape. AC loss comparison between monofilamentary conductors of rectangular, elliptical, square and round geometry has been performed in self-field and applied external perpendicular magnetic field. The areas of the cross-section and the superconducting-core-to-Ag ratio have been kept constant in the simulations. To complement the AC loss analysis, the distribution of the current density and the magnetic field of the different geometries are presented

Finite element method simulation of ac loss in HTS tapes with B-dependent E-J power law

The nonlinear behavior of High Temperature Superconductors (HTS) is often modeled by an E-J power law in order to describe their electromagnetic properties. This paper presents AC loss calculations in HTS tapes, performed by means of FEM commercial software using the A-V method. The implemented nonlinear model of the HTS tapes takes into account the B-dependence of the critical current density Jc and the power index n. The expressions for Jc(B) and n(B) are obtained from electrical measurements of a Bi-2223 tape under applied DC magnetic field. Numerical simulations of HTS tapes under different experimental conditions have been performed, i.e. the application of a transport current and/or AC external perpendicular magnetic field at 59 Hz. A comparative analysis of AC loss is then presented where Jc and n are maintained either constant or B-dependent. The combined Jc(B) and n(B) formulation leads to a better understanding of HTS electromagnetic behavior, especially when a perpendicular magnetic field is applied

Effect of the sheath resistivity and tape geometry on eddy current loss in Bi(2223) tapes

We have made a software electromagnetic simulation of eddy current effects in Bi(2223)Ag sheathed tapes with applied AC transport current in a broad frequency range. We have used simple models of monocore and multicore tapes. Calculated is the power distribution (W/m3) within the metal sheath using the geometry of real tapes. The numerical simulation is carried out with Finite-element-method software. The paper also describes the influence of the tape cross-sectional architecture and the sheath resistivity on the eddy current loss

Magnetic and electric simulation of eddy currents in Ag sheathed Bi2223 tapes

The use of HTSC tapes as main components in future power applications requires better understanding of their AC loss behaviour. Previous studies have lead to conclusions that eddy current loss is a significant loss factor at high frequency in self-field. In this paper we present a Finite Elements Method electromagnetic simulation of the current density and magnetic field distribution in the tape for 59Hz and 1kHz. The Ac losses due to eddy currents in the silver sheath are calculated for a mono and multicore tape. To carry out the electromagnetic simulation we have characterized the electric and magnetic properties of the superconductor using a simple model of a Bi2223 tape

Geometry considerations for use of Bi-2223/Ag tapes and wires with different models of Jc(B)

In typical power applications, Bi-2223 conductors carrying ac current will be subjected to external magnetic fields, whose orientation and conductor’s geometry are of major significance for the ac loss magnitude. This paper investigates the influence of the geometry and aspect ratio of non-twisted Bi-2223 conductors in reducing the ac loss for such applications. A numerical model of high-Tc materials has been used in finite-element-method simulations. The model incorporates power-law E-J characteristics with Jc and n defined by both parallel and perpendicular local magnetic field components. It allows computations of field and current distributions with transport current and/or applied field of any orientation. Monofilamentary tapes of rectangular and elliptical geometry with anisotropic Jc(B), as well as square and round wires with isotropic Jc(B) have been used for simulations under various operating conditions. A comparison between ac losses, magnetic field and current distributions in the tapes and wires is presented. It is demonstrated that depending on the orientation of the external field the difference of ac losses for non-twisted conductors with different geometry may reach one order of magnitude

Losses in HTS Tapes due to AC External Magnetic Field and AC Transport Current

The E-J power law as electric characterization of the HTS material in Finite Element computations has shown good agreement with measurements of field-dependent crtical current density and losses due to transport current. We use this technique to investigate the loss caused by Ac transport current in self-field and in applied AC magnetic field in both elliptical monocore and multicore tapes, where the current is generated by means of a voltage source. The current density is first kept constant and then varied with local magnetic field. Furthermore, the simulations show that the transfer current decreases due to the screening currents induced by the external field