This article proposes a fast and effective optimization procedure to achieve a low material cost of the ferrite permanent magnet assisted synchronous reluctance machine. The key is to achieve high pole utilization first and then limit the design margin of output torque and efficiency to reduce the material cost significantly. Moreover, a rotor overhang structure reduces material costs and improves space utilization. Four optimization steps with different functions are arranged, combining NSGA-II and NLPQL searching algorithms. First, establish the optimization model and parameterize the motor model according to the design requirements. Then, the arrangement of magnetic barriers and poles is optimized to achieve high pole utilization. Next, the split ratio, tooth width, stator axial length, and current are optimized to significantly reduce the material cost while limiting the design margin of output torque and efficiency. Finally, the rotor overhang structure increases the rotor axial length while reducing the stator axial length. With the proposed procedure, the material cost of a 36-slot, 6-pole PMaSynRM is reduced from $53.06 to $45.21 while meeting performance specifications. Furthermore, a prototype has been produced and tested to verify the effectiveness of the proposed procedure.

The inset-surface permanent magnet (ISPM) machine can achieve the desired electromagnetic performance according to the traditional deterministic design. However, the reliability and quality of the machine may be affected by the essential manufacturing tolerances and unavoidable noise factors in mass production. To address this weakness, a comprehensive multi-objective optimization design method is proposed, in which robust optimization is performed after the deterministic design. The response surface method is first adopted to establish the optimization objective equation. Afterward, the sample points are obtained via Monte Carlo simulation considering the design-variable uncertainty. The Design for Six Sigma approach is adopted to ensure the robustness of the design model. Furthermore, the barebones multi-objective particle swarm optimization algorithm is used to obtain a compromise solution. A prototype is manufactured to evaluate the effectiveness of the proposed method. According to the finite-element analysis and experimental tests, the electromagnetic performance and reliability of the machine are significantly enhanced with the proposed method.

This paper proposes a simplified lumped parameter thermal network (LPTN) model for thermal analysis under the inter-turn short-circuit (SC) faults of a five-phase fault-tolerant permanent magnet (PM) motor for electric vehicles. The proposed model can consider circumferential heat transfer, variable copper loss, and uneven loss distribution. Firstly, an analytical calculation formula of inter-turn SC current is proposed to separate the copper loss of SC turns from electromagnetic simulation, and the accuracy of the formula is verified by finite element analysis (FEA). Secondly, a simplified LPTN model is proposed, the calculation formulas of the thermal resistance are given, and the simplified principle is explained. By comparing the results of different simplifications, it is found that the error between the simplified model and the original model is small. Finally, the proposed model is verified by experiments. The results show that the simplified model can achieve not only a high calculation speed but also a high accuracy. Moreover, the proposed model is applicable to all cases of asymmetrical temperature distribution.

This paper presents an effective method to suppress torque pulsation and electromagnetic vibration. The key is to identify and suppress the space-time flux density harmonics that have a significant contribution to both torque pulsation and electromagnetic vibration. First, the mechanism of torque pulsation and electromagnetic vibration is investigated. Then, the contributions of different flux density harmonics are quantified considering the amplitude, phase, and space-time order. Meanwhile, the most critical flux density harmonics can be identified. Finally, a multi-objective optimization method combined with a symmetrically shaped rotor is used to optimize space-time flux density harmonic distribution. With the proposed method, a great improvement in torque and vibration performance of a 40-slot, 8-pole spoke-type permanent magnet motor is achieved. Furthermore, the method does not bring additional burden to manufacturing and does not increase material costs. Both the finite element model (FEM) and prototype results verify the effectiveness of the proposed method.

This article presents a particular flux-leakage that utilized a permanent magnet (FLUPM) rotor for ferrite spoke-type permanent magnet (STPM) motors to improve torque density. The key is to build a toroidal magnetic field (TMF) between the rotor yoke and N-pole, and TMF is only formed by the S-pole flux-leakage. In addition, to enhance the TMF, the S-pole usage is increased to generate more flux-leakage. Moreover, the magnetic barrier is reasonably designed to prevent flux flow to the shaft. Thus, a strong TMF utilizing S-pole flux-leakage is established. The TMF with strong flux shielding effect reduces the N-pole flux leakage, forcing more flux flow to the air gap. As a result, the flux-concentrated capacity of the rotor is significantly improved, thus enhancing the output torque. Through theoretical analysis, finite element simulation, and prototype test, it is confirmed that the FLUPM motor has a higher output capacity than the STPM motor already in mass production. Meanwhile, the torque ripple and cogging torque performance do not become worse. Furthermore, the FLUPM motor can achieve the IE5 energy-efficiency class with a lower material cost.

In this article, the influence of the atypical vibration source on the vibration of the hybrid rotor permanent magnet (HRPM) motor is analyzed. Accurate analysis and comparison of typical and atypical vibration source contributions to vibration are critical. First, the changes in the space-time order of radial forces resulting from the hybrid rotor structure are analyzed. Meanwhile, the total modulated radial force (TMRF) is calculated based on the force modulation effect. Next, a 3-D structural model is developed and verified for accuracy through modal experimentation. Then, the influence of typical and atypical vibration sources on vibration is analyzed, considering the amplitude, order, frequency, and distance from the natural frequency of TMRF. Finally, the vibration of the HRPM motor is predicted using the finite element simulation and experimental verification. Experiment results indicate that multiple additional low-order radial forces are generated due to the hybrid rotor structure. In addition, the contribution of atypical vibration sources to vibration is more significant than that of typical vibration sources in the HRPM motors. Thus, in the process of HRPM motor design, when analyzing its vibration characteristics, the influence of atypical vibration sources on vibration should be fully considered.