Shielding of ironless electrical machines

Abstract

Ironless motors are investigated for aviation applications because of their lightweight structure and high specific power. However, the removal of ferromagnetic materials creates an open magnetic circuit and increases magnetic flux leakage, which may cause electromagnetic interference (EMI) in sensitive aircraft environments. This thesis investigates magnetic shielding methods for high-temperature superconducting (HTS) ironless motors, focusing on active magnetic compensation and far-away iron yoke shielding. The principles, advantages, and limitations of both methods are analysed. Then, the far-away iron yoke method, which has a simple structure without adding cryogenics and superconductivity, is further studied using a two-dimensional finite element model in COMSOL Multiphysics. The results show that the far-away iron yoke can reduce the leakage magnetic field, and that both increasing yoke distance and increasing yoke thickness improve the shielding performance. It was also found that increasing the yoke distance is more effective on shielding than increasing the thickness.