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 effect, a validated three-dimensional (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 paper. The influences of field cooling height, pre-load and ambient temperature, were also studied and promising methods to improve the system stability were put forward according to the obtained conclusions. The above 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 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 is systematically studied in this paper, other potential applications such as thermal analysis of HTS bulk in pulse magnetization process, HTS bulkbased electrical machines, can also be expected in future work.

Modeling the charging process of a coil by an HTS dynamo-type flux pump

“…The segregated H-formulation (SEG-H) finite-element model, implemented in COMSOL Multiphysics, consists of a magnetostatic permanent magnet model and a timedependent H-formulation HTS wire model. The former is coupled unidirectionally to the latter using electromagnetic boundary conditions and a rotation operator to mimic the movement of the magnet [39][40][41]. This avoids the need for modeling moving parts (e.g., using a moving mesh) and significantly reduces the number of mesh elements, resulting in a fast and efficent model [42].…”

Modelling the Frequency Dependence of the Open-Circuit Voltage of a High-T c Superconducting Dynamo

“…The segregated model, implemented in COMSOL Multiphysics 5.4, consists of a magnetostatic PM model and a time-dependent H-formulation HTS wire model. The former is coupled unidirectionally to the latter using electromagnetic boundary conditions and a rotation operator to mimic the movement of the PM [20,34,35], as shown in Fig. 2.…”

Thermal Analysis of Modular Fault‐Tolerant Permanent Magnet Motor Based on Electromagnetic‐Thermal Bi‐Directional Coupling

“…In the low-frequency electromagnetic field, ignoring the displacement current, the correlation equation between Equation (1) and Equation ( 2) is [16]:…”