Repository logo
 

Influence of time-varying external magnetic fields on trapped fields in bulk superconductors


Loading...
Thumbnail Image

Type

Article

Change log

Authors

Zou, J 
Ainslie, MD 
Hu, D 
Cardwell, DA 

Abstract

Large, single-grain bulk high-temperature superconductors (HTS) can trap magnetic fields over 17 T below 30 K and up to 3 T at 77 K, and have significant potential to replace permanent magnets, the fields from which are limited to significantly less than 2 T. Therefore, bulk HTS samples are ideal candidates to develop more compact and efficient devices, such as actuators, magnetic levitation systems, flywheel energy storage systems and electric machines. In electric machines, in particular, the higher flux density improves the power density of the machine, resulting in smaller, lighter devices. However, in a real electric machine environment, bulk HTS samples can be exposed to AC magnetic field fluctuations that can affect the distribution of the supercurrent in the material and attenuate the trapped field, leading to a reduction in the magnetic loading of the machine, and in some cases, full demagnetisation. In this paper, the variation of trapped field with the frequency and magnitude of an external time-varying magnetic field is analysed numerically, and the mechanisms of the attenuation of the trapped field in HTS bulks are investigated using a two-dimensional (2D) axisymmetric finite-element model based on the H-formulation, considering both the electromagnetic and thermal behaviour of the bulk sample.

Description

Keywords

Finite element method, high-temperature superconductors, numerical simulation, trapped field attenuation, trapped field magnets

Journal Title

IEEE Transactions on Applied Superconductivity

Conference Name

Journal ISSN

1051-8223
1558-2515

Volume Title

25

Publisher

Institute of Electrical and Electronics Engineers (IEEE)
Sponsorship
Royal Academy of Engineering (RAEng) (10216/113)
This work was supported in part by a Henan International Cooperation Grant, China: 144300510014. . M. D. Ainslie would like to acknowledge financial support from a Royal Academy of Engineering Research Fellowship. D. Hu and J. Zou would like to acknowledge financial support from Churchill College, the China Scholarship Council and the Cambridge Commonwealth, European and International Trust.