We designed and analyzed an interior permanent magnet synchronous motor (IPMSM) to prevent irreversible demagnetization of the permanent magnets (PMs). Irreversible demagnetization of NdFeB PMs mainly occurs due to high temperature, which should thus be minimized. Therefore, it is necessary to reduce the eddy current loss in the PM through optimal design. The shape of the rotor core was optimized using finite element analysis (FEA) and response surface methodology. Three-dimensional (3-D) FEA is required for accurate computation of the eddy current loss, but there is huge time, effort, and cost consumption. Therefore, a method is proposed for indirectly calculating the eddy current loss of PMs using 2-D FEA. A thermal equivalent circuit analysis was used to calculate the PM temperature of the optimized model. For the thermal analysis, the copper loss, core loss, and eddy current loss in PMs were estimated and applied as a heat source. Based on the results, we confirmed the stability of the optimum model in terms of the PM demagnetization.

The post-assembly magnetizer for flux concentrated rotor of permanent magnet synchronous motor is dealt with in this paper. The design process of a magnetizer that is able to fully magnetize the permanent magnet (PM) inserted rotor core assembly within 3-times is discussed. The number of turns of the Main-pole winding and the Inter-pole winding was determined to maximize the magnetization ratio in each magnetization stage. At the same time, demagnetization characteristic is also examined. When the magnetizer is designed, the number of turns of winding is determined considering the eddy current generated in the core. The magnetization ratio of the PM considering the eddy current effect is compared with the magnetization ratio of the designed magnetizer when the eddy current effect is ignored. Finally, the properties of the finally designed magnetizer are verified through fabricated magnetizer and experiments.

Manufacturing uncertainties such as variations in material properties, dimensional tolerances, and assembly deviations of permanent magnets (PMs) significantly affect the mean and variance of key motor performances, including back electromotive force (back-EMF) and cogging torque. This study proposes a multi-response robust design optimization method that simultaneously improves the mean and variance of the back-EMF and cogging torque, thereby mitigating the performance variations caused by manufacturing tolerances in an integrated starter generator (ISG) type electric oil pump (EOP) motor. First, significant design variables were identified through a first-order Taylor series-based approximated variance and analysis of variance (ANOVA), to reduce dimensionality. Sampling points were generated using a combination of Latin hypercube design (LHD) and sequential maximin distance design (SMDD), and a Kriging surrogate model was constructed and validated through normalized root mean square error (NRMSE). The Derringer–Suich desirability function and relevant constraints were then applied, and robust solutions were obtained using sequential quadratic programming (SQP). To set desirability targets, 10,000 LHD samples were used to explore feasible designs satisfying the voltage constraint, and the knee region of the resulting mean–variance trade-off distribution was utilized. Finally, the robust design was validated using 106 Monte Carlo simulation (MCS) runs, confirming improved robustness compared with the present design while substantially reducing the number of expensive finite element analysis (FEA) evaluations required for robust optimization. The proposed framework provides a practical and robust design pathway for improving the quality consistency under permanent magnet (PM) manufacturing tolerances.