3차원 자계 해석을 이용한 초전도 회전기기 설계

Abstract

Design of superconducting rotating machine using high temperature superconducting (HTS) wire in field winding has been an important issue for size, weight reduction and high efficiency. Because of high current density of the HTS wire, the HTS wire can produce high magnetic field compared with copper wire. Therefore, the superconducting rotating machine has been used in low-speed / high-capacity wind generator, ship propulsion motor, and so on. On the other hand, the superconducting rotating machines have 3-dimensional (3D) magnetic field distributions because they have large magnetic air-gap due to slotless air-cored winding, damper, and cooling structure. Therefore, in order to predict characteristics of the superconducting rotating machines, 3D analysis should be performed. However, 3D analysis, such as finite element analysis (FEA), has complex preprocess and takes a very long computation time. Accordingly, in order to overcome the weakness of 3D-FEA, 3D magnetic field analysis using analytical method is necessary. This dissertation deals with a design of superconducting rotating machine using 3D magnetic field analysis. In order to perform the 3D magnetic field analysis, analytical method which applies combination of space harmonic analysis (SHA) and image method (IM), is proposed. Firstly, 2-dimensional (2D) flux density distributions are calculated by SHA. Secondly, 3D weighting factor for flux density variation according to the change of z-axis position is calculated in IM. Finally, the 3D weighting factor is multiplied to the 2D flux density distributions, and then the 3D magnetic field distributions of the superconducting rotating machine are calculated. Using the 3D magnetic field distributions, electrical parameter and magnetic stress are calculated and the validity of the proposed method is compared with 3D-FEA. Therefore, 3D magnetic field analysis using the proposed method is used in design process of superconducting rotating machine. Especially, in order to verify a reliability of superconducting rotating machine in the design process, magnetic field distribution at field winding is investigated by sudden-short analysis. Lastly, design of low-speed / high-capacity superconducting motor and generator is performed, and then its volume and weight are compared with those based on 2D magnetic field analysis. From those comparisons, the effects of 3D magnetic field analysis in the design of superconducting rotating machine are verified.