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Dual airgap stator- and rotor- permanent magnet machines with spoke-type configurations using phase-group concentrated-coil windings

This paper presents an advanced design procedure for stator-based and rotor-based permanent magnet (PM) machines with spoke-type PM configurations for the comprehensive improvement of electromagnetic performance including torque/power density, efficiency, cogging torque, and torque ripple. The dual-rotor switched flux PM machine (SFPMM), designated as the stator-PM machine, and the dual-stator spoke-type interior PM machine (S-IPMM), termed the rotor-PM machine, are investigated with the proposed design method for direct-drive applications, in which the phase-group concentrated-coil windings and an unaligned arrangement of two rotors/stators are utilized, with the aim of enhancing the flux focusing effects for high torque density and suppressing pulsating torques. To evaluate the contribution of the proposed design mechanism on machine performance, a conventional SFPMM with concentrated windings is adopted as the reference model. For a fair comparison, all the investigated machines are designed with the same dimensions, and their performance including back electromotive force (EMF), cogging torque, and electromagnetic torque are analyzed by a finite element method (FEM) under the same operating conditions. Finally, a prototype of the dual-stator S-IPMM is manufactured, and some key simulation results are verified by experimental measurements.