A Comprehensive Comparison of Double-Stator Superconducting Brushless Machines Using Two Typical Field-Excitation Stator Topologies

This paper presents a comprehensive comparison of double-stator superconducting (SC) brushless (DS-SCB) machines using two different field-excitation stator topologies: a conventional radial-type and a newly developed quasi-spoke-type. Firstly, a set of critical dimension equations for the field-excitation stator are derived based on the modular SC magnets. Subsequently, the radial-type and quasi-spoke-type I and II machines are compared in terms of operating mechanisms, magnetic circuits, no-load back-EMF, output torque, power factor, dc-winding-induced voltage, magnetic field distribution around SC wires, and the eddy current losses of modular SC magnets. The results indicate that the choice of field-excitation stator topology depends on the magnitude of a field-excitation magnetomotive force due to SC current (F_SC). At high excitation fields, the quasi-spoke-type stator offers several advantages for the DS-SCB machines, including high power density, improved power factor, and a significant reduction of approximately 85∼98% in eddy current loss of modular SC magnet. Prototype experiments are also conducted to verify.