This paper presents an optimal design of a recently introduced brushless wound-rotor synchronous machine (BL-WRSM). The BL-WRSM, with a special stator winding arrangement, utilizes a single three-phase inverter for generating an additional spatial subharmonic component in the stator magnetomotive force (MMF). This subharmonic component of the stator MMF is used for the brushless excitation of the rotor. The pole span and pole shoe height were the optimized parameters, with the goals of improving the quality of output power and reducing torque ripple. Moreover, the average torque of the machine was improved by optimizing the harmonic winding placed on the rotor. The optimized BL-WRSM was further analyzed for the flux weakening operation. Finite element analysis (FEA) was carried out to analyze the performance of the BL-WRSM. Finally, the performance of the optimal BL-WRSM model was verified through an experimental test, which demonstrated good agreement with the simulation results.
This paper proposes a novel dual-rotor, axial field, fault-tolerant flux switching permanent magnet machine (FSPMM) with high torque performance for direct-drive applications, in which the phase-group concentrated-coil windings and unaligned arrangement of the two rotors are utilized. The adoption of the phase-group concentrated-coil windings is made to obtain a unity displacement winding factor, and to enhance the flux focusing effects together with the use of a spoke-type PM configuration. The unaligned arrangement of the two rotors will help to achieve increased flux magnification and also to suppress the cogging torque and torque ripple. In particular, the proposed configuration for FSPMMs exhibits the advantage of fault tolerance benefiting from the electromagnetic isolation of phases and a dual three-phase channel of supply. The operating principle and design criteria of the proposed FSPMM are discussed in detail. To highlight the advantages of the proposed FSPMM, two conventional FSPMMs are adopted for comparison under the same operating conditions based on a 3-D finite element method (FEM). As a result, it is demonstrated that the proposed FSPMM exhibits significantly improved performance with not only higher torque (power) density but also lower cogging torque and torque ripple, compared to the conventional FSPMMs.Index Terms-Axial field, direct-drive, fault tolerant, finite element method (FEM), flux switching permanent magnet machine (FSPMM), phase-group concentrated-coil winding, torque, winding factor.
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