This paper presents a field-modulated permanent magnet (FMPM) machine using spoke-magnet-array outer rotor for direct-drive applications. The operating principle with detailed theoretical derivation is analyzed to reveal the evidence for high torque capability of the proposed machine, just due to the utilization of effective harmonic flux adding to the contribution of air-gap fundamental flux for energy conversion. Using the finite element analysis, the performance characteristics of the

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... d machine are assessed and compared with permanent magnet synchronous machine counterparts to verify the theoretical analysis. A prototype machine is also fabricated for experimental validation of the proposed machine. The analytical discussions also form an important foundation for research in various high-performance FMPM machines. . His current research interests include analysis, design, and control of permanent-magnet machines. Kwok tong Chau (M'89-SM'04-F'13) received the B.Sc. (Eng.) (Hons.), M.Phil., and Ph.D. degrees in electrical and electronic engineering from the University of Hong Kong, Hong Kong, in 1988Kong, in , 1991Kong, in , and 1993 He is currently a Full Professor with the Department of Electrical and Electronic Engineering, University of Hong Kong, where he is also the Director of the International Research Center for Electric Vehicles. He has authored four books, seven book chapters, and over 180 refereed journal papers. His current research interests include electric and hybrid vehicles, machine and drives, and clean energy. Ming Cheng (F'15) received the B.Sc. and M.Sc. degrees from the Department Vehicles. He has authored over 250 technical papers and four books, and holds over 50 patents in these areas. His current research interests include electrical machines, motor drives for electric vehicles, and renewable energy generation. Byungtaek Kim (M'01) was born in Seoul, Korea. He received the B.S., M.S., and Ph.D. degrees in electrical engineering from Hanyang