An improved FEM model for computing transport AC loss in coils made of RABiTS YBCO coated conductors for electric machines

Abstract

AC loss can be a significant problem for any applications that utilize or produce an AC current or magnetic field, such as an electric machine. The authors investigate the electromagnetic properties of high temperature superconductors with a particular focus on the AC loss in superconducting coils made from YBCO coated conductors for use in an all-superconducting electric machine. This paper presents an improved 2D finite element model for the cross-section of such coils, based on the H formulation. The model is used to calculate the transport AC loss of a racetrack-shaped coil using constant and magnetic field-dependent critical current densities, and the inclusion and exclusion of a magnetic substrate, as found in RABiTS (rolling-assisted biaxially textured substrate) YBCO coated conductors. The coil model is based on the superconducting stator coils used in the University of Cambridge EPEC Superconductivity Group's all-superconducting permanent magnet synchronous motor design. To validate the modeling results, the transport AC loss of a stator coil is measured using an electrical method based on inductive compensation by means of a variable mutual inductance. Finally, the implications of the findings on the performance of the motor are discussed.

Influence of soft ferromagnetic sections on the magnetic flux density profile of a large grain, bulk Y–Ba–Cu–O superconductor

“…The numerical model developed here combines the electromagnetic equations governing the behaviour of the superconductor based on the 2D axisymmetric H-formulation [39][40][41][42] with the same modifications made to include magnetic subdomains with a relative permeability μ r (H) as described in [25,26,43,44].…”

Development of a three-dimensional finite-element model for high-temperature superconductors based on the H-formulation

“…In particular, the H-formulation [1,2] has increased in popularity both in the academic and the industrial world and it has been successfully used to study the ac loss performance not only of individual wires, but also of more complex systems like cables and coils [3][4][5]. The model has been adapted to take into account the presence of ferromagnetic materials as well [6,7]. Until now, the model has been only used to simulate 2-D problems, i.e.…”

Electromagnetic behaviors of superconducting Nb3Sn wire under a time-dependent current injection

“…2 In recent years, attempts have been made to study the electromagnetic behaviors of some superconductors by numerical simulation. [3][4][5][6][7][8][9][10][11][12][13][14][15][16] As for finite element modelling (FEM), the extreme complexity of hierarchical geometry and structure of Nb 3 Sn strand and CICC requires a special concern for the modelling of the strand entity. Therefore this will inevitably consume large amounts of CPU time and memory capacity in meshing and calculating process.…”

“…So, 2D simulations mainly focus on high-temperature superconductors (HTS) with homogenous material and standard bulk shape. 3,4,6,[8][9][10][11][13][14][15] As the advance of computer technology, it becomes feasible to use FEM to cope with Nb 3 Sn strand at the cost of long-time computation and large memory. Even so, modelling the strand down to filament level is still troublesome.…”