Study on Electromagnetic-Thermal Characteristics of Bi-2223 Tape by Homogenization Model

Bi-2223/Ag multifilament superconducting tape has high critical temperature, high critical current, and low loss, which has great application potential in superconducting power devices. However, it is a multifilament structure, and it takes a long time to use the finite element method (FEM) to simulate its electromagnetic and thermal properties. A method called “homogenization” is applied to quickly evaluate the electromagnetic characteristics of multifilament tape under normal alternating current. However, further research is needed to determine the applicability of the homogenization model under fault currents. In this paper, we use the electromagnetic-thermal coupling model to compare and analyze the loss and temperature change of the original model and the homogenization model tape under normal alternating current and fault current. Under normal alternating current, the temperature rise of the tape can be ignored, so the influence of temperature on the loss of the tape can be ignored. At this time, the homogenization model can quickly and effectively evaluate the AC loss of multifilament tape. Under the fault current, when the fault degree is small (Ip/Ic0 is less than 1), the tape temperature rise is not obvious, and the difference between the two models is small. At this time, the homogenization model can still quickly and effectively evaluate the loss of multifilament tape. When the fault degree is large (Ip/Ic0 is greater than 2), the temperature rise of the tape obtained by the two models is significantly different, so the tape loss obtained by the two models is somewhat different. At this time, the homogenization model should be carefully selected to describe the loss of multifilament tape.

I. Introduction

Bi-2223/ag multifilamentary high temperature superconducting (HTS) tape has excellent electromagnetic, thermal and mechanical properties and high superconducting transition temperature (105 K–110 K), showing attractive potential in the field of electric power apparatuses such as power transmission cables, motors, generators, transformers, and fault current limiters [1], [2], [3], [4], [5], [6], [7], [8], [9]. Numerical simulation is needed to optimize the design of superconducting devices made of multifilamentary superconducting materials. Due to a large number of filaments of multifilamentary tape or wire and the small size of filaments, this will lead to a long calculation time and a large amount of memory [10], [11], [12], [13], [14], [15]. Especially when the cable or magnet is made of multifilamentary tape or wire, the numerical evaluation of its electromagnetic characteristics becomes more difficult.