A permanent magnet synchronous reluctance machine (PMSynRM) is studied in this article. It has a stack of surface-mounted permanent magnet (SPM) rotor and a stack of synchronous reluctance (SynR) rotor, which are axially combined on the shaft. Unlike the traditional PM-assisted SynR machine (PMASynRM), the magnets are not located in the flux barriers of the SynR rotor, and therefore, the magnets and flux barriers have no more geometric confliction between them. The two rotor stacks can be circumferentially shifted to any relative angle. Clearly, the shifting angle and the axial length ratio between the two rotor stacks, together with the phase angle of the armature current vector, influence the motor performance, and their optimal design is detailed in this article. Analysis of the prototypes shows that the studied PMSynRM evidently exhibits higher torque density than the conventional PMASynRM.

This paper presents an improved mathematical model of high-speed permanent magnet synchronous machine (PMSM), taking the rotor eddy current reaction effect into account. The conventional model (e.g. MATLAB/Simulink built-in PMSM model) is not capable of handling the high-frequency behaviors of the high-speed PMSM which involves rotor eddy current reaction field. Such behaviors include, for example, the decrease of armature winding inductance with frequency, and the increase of harmonic current amplitude under PWM voltage source inverter (VSI) power supply. In the improved model, the rotor eddy current reaction effect is modeled by setting up short-circuited virtual windings on the rotor reference frame. The parameters of the rotor virtual windings can be identified with a standstill frequency response (SSFR) test using either finite-element (FE) method or direct experimental measurement. Finally, the advantage of the improved PMSM model over the conventional one is verified with both SSFR and on-load experimental test with a 300 kW, 26 krpm high-speed PMSM prototype.

In high-speed surface-mounted permanent magnet (SPM) brushless machines, time- and space-harmonic excitations can induce significant eddy currents flowing in the rotor conductive parts. An effective measure to suppress the eddy currents is to employ a copper shield between the magnets and the retaining sleeve. In this article, a Fourier-based analytical model is proposed to evaluate the rotor eddy current losses. The model is set up in the cylindrical coordinate system and is able to compute the eddy current fields and losses in all rotor domains, that is, the sleeve, shield, magnets, and shaft. Although it is generally believed that both ordinary Bessel functions (OBFs) and modified Bessel functions (MBFs) are workable for solving the magnetic vector potential, it is argued in this article that only the MBF-based models are numerically stable when the high-conductivity domain (e.g., the copper shield) exists, while the OBF-based models may result in irrational results. Both the OBF- and MBF-based analytical models for a prototype motor are established and comparatively studied, with verification of the finite-element (FE) method. Moreover, the cause of losing analysis accuracy in the OBF-based models is revealed.

Post-assembly magnetization can significantly simplify the manufacturing of the rotor of permanent magnet (PM) electrical machines. The optimization of the post-assembly magnetizing device using finite element analysis (FEA) is time-consuming; therefore, a globally optimal solution aiming at achieving an adequate magnetizing level and minimal energy consumption is difficult to achieve. In this paper, a field–circuit coupling analysis (FCCA) model is proposed to optimize the auxiliary stator-type magnetizing device for interior permanent magnet synchronous machines (IPMSMs). A reasonable simplification of the highly saturated magnetic circuit is made based on FEA results so that the magnetic equivalent circuit (MEC) model can be established. On the other hand, the eddy currents in the PMs are equivalent to an eddy current short-circuit; thus, by converting the field calculation into a circuit calculation, the time cost can be reduced significantly, which greatly improves the speed of multi-objective optimization of the magnetizing device with multiple degrees of freedom. A V-type IPMSM is taken as a study case, and its post-assembly magnetizing device is optimized with the proposed method. FEA and experimental results show that the PMs are fully magnetized, while the required energy consumption is greatly reduced when compared with an existing magnetizing device.

The electromagnetic force plays a significant role in contributing to torque ripple and electromagnetic vibration in permanent magnet synchronous machines (PMSMs), thereby impacting the noise, vibration, and harshness (NVH) performance. However, in most cases, existing design and analysis approaches predominantly focus on torque ripple, radial force and vibration under the stator reference frame, which is not sufficiently comprehensive. To address this gap, this paper presents the derivation of the spatial and temporal orders of force harmonics under both the stator stationary reference frame and the rotor rotating reference frame. Through theoretical analysis and finite element method (FEM) simulations, this paper highlights the differences in force harmonics and vibrations between the two reference frames. Furthermore, it explores the relationship between torque ripple and vibrations under different reference frames. Additionally, the superposition and cancellation effects of radial and tangential forces in producing vibrations are investigated. Finally, to validate the theoretical analysis, two prototypes of PMSMs with 6 poles and 9 slots have been manufactured and subjected to performance testing.