A New Hybrid Excitation Permanent Magnet Machine With an Independent AC Excitation Port

This paper proposes a novel hybrid excitation permanent magnet (PM) machine with an independent ac excitation port to extend the speed range and improve the torque capability. The proposed machine is characterized by an axial stator placed in one side of the rotor, which provides a shunted flux path of the radial stator. The prominent merit of the proposed machine is that it can make better utilization of the PM flux and offer a large flux regulation capability because the radial flux and the axial flux are in parallel to each other. Thorough analysis of the field distribution is performed by three-dimensional (3-D) finite-element analysis, and different operation modes of the proposed machine are illustrated and compared. Then, the flux regulation capability of the machine is analyzed using the simplified magnetic equivalent circuit, which is proved to give reasonable precision, indicating that the flux regulation ratio only depends on the design parameters of the ac excitation port. Finally, a 36-slot/six-pole prototype using the proposed configuration is built and tested. It is verified that the proposed machine exhibits excellent performance of flux regulation, thus offering a good potential to be used in wide-speed-range driving applications.