This paper presents the design and analysis of a novel permanent-magnet (PM)-assisted synchronous reluctance machine (PMA-SynRM) with axially integrated magnets for improving machine performance by using a finite-element method (FEM). The proposed PMA-SynRM features a simple structure with high performance by incorporating the advantages of a SynRM and a surface-mounted PM machine (SPMM). In particular, the rotor parts of the SynRM and SPMM are assembled to make the “q-axis” located 45° (elec.) from the d-axis. Thus, the magnetic torque and reluctance torque of the proposed PMA-SynRM reach the maximum values at the same current phase angle, for efficient production of the total torque. To highlight the advantages of the proposed PMA-SynRM, a conventional PMA-SynRM is adopted for comparison under the same operating conditions. The FEM analysis results finally demonstrate that the proposed PMA-SynRM has a higher total torque and power factor, as well as greatly reduced torque ripple, when compared to the conventional PMA-SynRM with the same magnet amounts. In addition, the Mises stress analysis indicates that the configuration of the proposed PMA-SynRM exhibits the advantage of avoiding stress deterioration in the rotor ribs.

This paper proposes a new hybrid permanent magnet synchronous reluctance machine (HPM-SynRM) with axially sandwiched magnets for improving machine performance including airgap flux density, back electromotive force (EMF), torque, torque ripple, efficiency, and power factor. The significant feature of the proposed machine is the configuration of axially integrating two kinds of independent and symmetrical rotors with a specific assembling angle, such that it can make full use of the magnetic torque and the reluctance torque for efficient production of the total torque. Meanwhile, the proposed machine greatly improves the PM utilization for high magnetic torque, and releases the stress condition of SynRM rotors for more proper design of ribs, thus to further improve the torque, efficiency, and power factor, especially when compared to the conventional PM-SynRM with the same machine specifications and operating conditions. The design of the proposed machine, including the PM optimization using the Kriging method and genetic algorithm, rib width and assembling angle design using the finite element method (FEM), has been first discussed in detail. Then the advantages of the proposed machine is highlighted by quantitatively comparing to a conventional PMSynRM by the FEM. Finally, the proposed machine is manufactured to validate its high performance by experiments.

Accurate calculation of the natural frequencies of the stator is an important premise for improving electromagnetic vibration and noise. In order to improve the calculation accuracy of the natural frequencies of the stator, the influences of the tooth feet and tooth shoulders are fully considered, the stator core and enclosure are regarded as cylindrical shells with axial ribs attached inside and outside the shells, respectively. Considering the moment of inertia and the transverse shear deformation of the cylindrical shells, the vibration displacement of the continuous system is dispersed by Galerkin dispersion and Rayleigh-Ritz method, the characteristic equations of the stator under free vibration are derived based on the three-dimensional shell theory, and the natural frequencies of the stator with anisotropic material are obtained. In addition, the calculation method of stator natural frequencies under different boundary conditions is given. Further, the natural frequencies of the end cover and the entire motor are analyzed. In order to verify the accuracy of the calculation method, the natural frequencies of a stator are calculated by the finite element method (FEM) and the hammering method. The results obtained by the calculation method in this paper are in good agreement with the experimental results.

Slight electromagnetic vibration is one of the crucial indicators that must be considered in the motor design stage. Considering the influence of complex stator slot structure and inevitable saturation at slot opening, a permeance calculation model suitable for the motor with any pole-slot combination is introduced, and the electromagnetic force waves of the motor are calculated quickly and accurately. Considering the orthogonality of stator material and the influence of enclosure and windings, the natural frequencies of the entire stator are analyzed, and the vibration accelerations are calculated by the multiphysics model including control, electromagnetic, structural, and vibration models, the accuracy of the calculation results is verified by the prototype test. Furthermore, the components of electromagnetic force waves that have great impact on electromagnetic vibration are summarized, a weakening method of electromagnetic vibration based on the optimization of the stator slot parameters is proposed, and the optimal stator slot parameters are obtained by the simplified model and the accurate model combining deep neural network (DNN) and immune clone algorithm (ICA), respectively. For the 6-pole 36-slot motor, the vibration accelerations near the six-order natural frequency are greatly reduced by optimizing the stator slot parameters based on the accurate model combining DNN and ICA, and the maximum vibration accelerations are reduced by 34.1% at no load and 36.8% at rated load.

Line-start permanent magnet synchronous motors (LSPMSMs) have become superior to induction motors in general industrial applications due to their high efficiency, improved power factor, and enhanced torque density. However, the LSPMSM suffers the poor starting torque owing to the existence of the braking and pulsating torque at start-up, which seriously plagues its development. Therefore, this paper presents a novel LSPMSM with 6/8 pole changing stator windings, which can fundamentally improve the starting capability. At the beginning of the starting, the 6-pole stator windings are energized, whereas the rotor permanent magnets are 8 poles, so the braking torque and pulsating torque can be highly decreased. When the motor reaches a certain speed, the stator winding changes to 8 poles to pull into synchronization and stable operation. The design of the 6/8 pole changing winding is presented based on the slot-number phase diagram method. Then, the starting process of the conventional and the proposed pole changing LSPMSMs are analyzed and compared. Through the calculation of impedance parameters and the analysis of magnetic fields at the start-up, the torque components are calculated utilizing the analytical calculation method. Finally, the experiments are carried out to verify the validity and superiority of the proposed design and method.

This article presents an analytical method to predict the magnetic field of eccentric surface-mounted permanent magnet synchronous machine (SPMSM) by applying the hybrid magnetic circuit and subdomain method. Taking stator saturation into account, the surface current is appended to the stator coil conductor, which can generate a magnetomotive force (MMF) to compensate the MMF drop across the stator core. The rotor yoke saturation effect is modeled by increasing the air-gap length. To solve the problem resulted from rotor eccentricity in analytical analysis, an equivalent transformation method is given. The transformation principle is that the eccentric machine can be equivalent to a concentric one with redistributed PM remanence and armature current density. On this basis, the subdomain method is adopted to predict the magnetic field of the reestablished machine. The proposed analytical method is implemented and evaluated on the 6p/36s and 8p/12s SPMSM and exhibits good agreement with the FEM and experiment results.