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Abstract High torque density and high reliability motors have a wide application prospect in aerospace field, so a hybrid rotor and dual stator motor is studied in this paper. Firstly, to address the problem that the difference in power density between the inner and outer unit motor is so large that it is not suitable for electromagnetic design using the power splitting method, a main dimensioning calculation method based on the equal‐power volume transformation is proposed. The influence of thermal load on the output performance of the inner and outer unit motors is taken into account comprehensively. The main dimensioning expressions for such motors are derived. Secondly, the output performance consistency between the inner and outer unit motors is theoretically analysed, and the optimal angle between the d‐axis of the permanent magnet rotor and the d‐axis of the reluctance rotor is obtained when the motor is operated in the maximum torque per ampere control mode. Finally, a prototype with a rated power of 46.7 kW was developed and load experiments were conducted on it, and the experimental results verified the correctness and feasibility of the theoretical analysis method.

Abstract Compared with a traditional low‐speed high‐torque permanent magnet synchronous motor (PMSM), a permanent magnet (PM)/reluctance hybrid rotor dual‐stator synchronous motor (PM/RHRDSSM) has the advantages of high torque density and high space utilization. This type of motor is composed of a "back‐to‐back" PM + reluctance hybrid rotor and an inner and outer double stator. The number of poles of the inner and outer unit motors is the same, and the inner and outer stator windings are connected in series, driven by a single inverter. Due to the special mechanical structure and electromagnetic relationship of PM/RHRDSSM, traditional PMSM and synchronous reluctance motor maximum torque per ampere (MTPA) control strategies are no longer applicable. In response to this issue, the authors establishe a PM/RHRDSSM mathematical model of stator winding series structure and propose a MTPA control strategy suitable for this new type of motor. This strategy is aimed at the special mathematical model of PM/RHRDSSM and derives the analytical expression of MTPA trajectory, which minimises the required stator current amplitude of PM/RHRDSSM at various load torques, thereby minimising the motor copper loss. Finally, the effectiveness and practicality of the proposed control strategy were verified through simulation and experiments.

Abstract Permanent magnet synchronous motor (PMSM) shows the great potential for use in direct drive system because of its excellent low‐speed direct‐drive capability. However, it suffers from the adverse effect of the cogging torque in comparison with the asynchronous motor. Therefore, reducing the cogging torque, especially the external‐rotor PMSM (ERPMSM) for belt conveyor application, is necessary for enhancing the stable operation and precise positioning performances of the belt conveyor.Herein, a novel tangential magnetization low‐speed high‐torque ERPMSM is proposed and analysed. Furthermore, the expression of the cogging torque of the proposed ERPMSM is derived by energy method. Based on the special structure of the ERPMSM, a new method for cogging torque reduction is introduced. The comparative FEA results for four ERPMSM models are presented to verify the accuracy and effectiveness of this method. The accuracy of the cogging torque FEA results is confirmed by a prototype. Finally, the influence of this method on ERPMSM performance is also analysed carefully in this paper.