Comparison of Excitation Topologies for Fully Stator-HTS Fault-Tolerant Machines

This paper proposes four topologies for high-temperature superconductor (HTS) fault-tolerant machines. Since the excitation ways of HTS field coils have significant effect on electromagnetic performances, four HTS machines with different HTS field coils are proposed, analyzed, and compared. For a fair comparison, their same rotors and dimensions are designed. Although their stators and field coils are different, these four machines have some common features. Namely, only one cooling system is required. This is because their HTS armature coils and HTS field coils are placed in the stator. Meanwhile, the fault-tolerant teeth (FTT) are adopted. These FTT not only provide extra flux path to improve torque capability but also decouple adjacent phases physically and magnetically, thus enhancing fault-tolerant capability. Finally, the characteristics of the HTS are analyzed and finite-element results are given for verification.