Regular Article

Magnetization reduction by varying normal field in stacks of composite superconductors in an electrical motor^★

¹ Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, UK
² Oswald Elektromotoren GmbH, Miltenberg, Germany
³ Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, UK
⁴ Institute of Power Engineering, Warsaw, Poland

^* e-mail: as2903@cam.ac.uk

Received: 3 February 2020
Received in final form: 19 June 2020
Accepted: 20 July 2020
Published online: 20 November 2020

Abstract

Trapped field magnets of superconducting stacks could be an alternative to conventional magnets in electrical machine applications. A conceptual design of an electrical motor using these stacks was proposed in [1,2]. Superconducting stacks offer many advantages; however, they can be demagnetized when exposed to the varying field present in electrical motors during operation. This varying field can be generated by salient magnetic circuit or generated from the armature winding as harmonics. To study this demagnetization effect, we carried out an experiment on a superconducting stack in an electrical machine, exposing it to different levels of varying cross and normal fields. The experimental measurements recorded a demagnetization of the stack. In this work, the analyses of the reduction of magnetization of the superconducting stack by an alternating normal field and the comparison of the results with experimental measurements in the electrical motor are presented.