A 3-D Strong-Coupled Electromagnetic-Thermal Model for HTS Bulk and Its Uses to Study the Dynamic Characteristics of a Linear HTS Maglev Bearing

Abstract

Thermal effect will greatly affect the engineering performance of high-temperature superconductors (HTSs) due to its strong dependence of electromagnetic parameters upon the local temperature. To advance the understanding of such thermal effects, a validated 3-D strong-coupled electromagnetic-thermal model for HTS bulk was established in commercial finite-element software COMSOL, which ensures the easy access and universality of the model. Jc(B,T) was employed to reflect both magnetic field and thermal field dependences of HTS in this model. In addition, the thermal transient equation and convective boundary condition were employed with experimentally measured HTS thermal conductivity and heat capacity to describe the thermal flux exchange between HTS and cryogenic medium. As an example of application, the established electromagnetic-thermal model was tailored to study the dynamic characteristics of a linear HTS magnetic levitation (maglev) bearing. The methodologies to numerically study the dynamic response of the linear HTS maglev bearing under free vibration state and typical operating excitations, e.g., earthquake, track irregularity, and crosswind, were put forward in this article. The influences of field cooling height, preload, and ambient temperature, were also studied, and promising methods to improve the system stability were put forward according to the obtained conclusions. The above-mentioned results are reasonable and keep in concert with former experimental and theoretical studies. Moreover, some results which are inaccessible in the 2-D models, for instance, the thermal field distribution inside HTS bulk, can also be obtained due to the versatility of the 3-D model. To conclude, the established HTS electromagnetic-thermal model could serve as a flexible and extensible simulation tool to study various applications of HTS bulk. Besides the application in linear HTS maglev bearing, which was systematically studied in this article, other potential applications, such as thermal analysis of HTS bulk in pulse magnetization process and HTS bulk-based electrical machines, can also be expected in future work.