Overview of Flux-Modulation Machines Based on Flux-Modulation Principle: Topology, Theory, and Development Prospects

With the development of electrical machines, traditional machine theory can no longer explain the operation principles of some new type machines, such as vernier machine and stator PM machine. The principle of flux modulation (FM) provides an important direction for the development of machine theory. This article overviews the development of the FM machine regarding its principle and topology. According to the studies on the FM effect of different types of electrical machines, it can be found that the FM principle is universal in electrical machines. However, the studies on the FM principle are still limited to some specific machines at present, and it leads to the fragmentation of theory. A new general air-gap FM theory is introduced, and it can be expected to be the unified theory for electrical machines. To verify the correctness of the new theory, some electrical machines, including induction machine and nonsalient pole machine, are analyzed by the general air-gap FM theory. In addition, the design and engineering application of the FM machine and theory are analyzed. To verify the inherent unity of the electrical machine, the topology evolutions of the FM machine are also discussed. Based on the new general air-gap FM theory, the innovative methods of topology can be summarized, while the development prospects of the FM machine are subsequently discussed.