Analysis of Superconducting Synchronous Motors With Halbach Array Field Excitation

This article evaluates the novel design approach of a 3 MW partially superconducting synchronous machine for electric aircraft propulsion. Its special feature is the application of an electromagnetic Halbach array for the field excitation to reduce the back yoke weight and thereby increase the overall output power density. The electromagnetic Halbach array is obtained by reproducing a permanent magnet Halbach array with high-temperature superconducting coils. The arrangement is further optimized, and its field characteristics are compared to a conventional superconducting field winding design. Even though the Halbach array has a higher space and superconductor consumption, it shows better characteristics concerning the intensity of inside and outside magnetic field. Applied in a superconducting motor, the Halbach array field winding achieves a back yoke thickness reduction of up to 85% and a back yoke weight reduction of up to 78% compared to reference models. The gravimetric power density is increased by up to 30% at the expense of volumetric power density. In exchange for a back yoke weight reduction, other components, such as field winding and cryostat, become heavier.