This study investigates the tapering rotor surface technique in an interior permanent magnet synchronous motor (IPMSM) for electric vehicle compressors. To achieve this, this article proposes a novel tapered rotor design with a nonuniform air gap, created by applying asymmetric shaping to the bridge region along the rotor radius. A conventional IPMSM with a uniform air gap produces a trapezoidal-shaped flux density, introducing high-order harmonics and causing certain drawbacks for the motor. This study selected the offset height of the eccentric center and the distance between the rotor radius and the magnet as improvement design variables. The proposed tapered rotor model, characterized by a nonuniform air gap, demonstrated better performance than the initial model. Subsequently, a stress analysis of the thinned barrier was conducted to validate the structural integrity of the proposed model. The key parameters, such as air-gap flux density, cogging torque, inductance, flux linkage, and efficiency maps, were compared between the initial and improved models using finite element method (FEM) and MATLAB simulations. The proposed tapering motor achieved a 36.36% reduction in cogging torque error rate and a 0.6% improvement in efficiency deviation at the primary operating point. A prototype of the conventional rotor model was manufactured, and its efficiency curve was verified, which showed good agreement with the FEM analysis results.

This paper presents the design of a permanent-magnet-assisted synchronous reluctance motor (PMa-SynRM) for compressor applications using Sm-series injection-molded magnets that eliminate heavy rare-earth elements. The high shape flexibility of the injection-molded magnets enables the formation of a curved multi-layer flux-barrier rotor geometry based on the Joukowski airfoil potential, optimizing magnetic flux flow under typical compressor operating conditions. Furthermore, electromagnetic performance, irreversible demagnetization behavior, and rotor stress sensitivity were analyzed with respect to key design variables to derive a model that satisfies the target performance requirements. The validity of the proposed design was confirmed through finite element method (FEM) comparisons with a conventional IPMSM using sintered NdFeB magnets, demonstrating the feasibility of HRE-free PMa-SynRM for high-performance compressor drives.

This study focuses on improving the efficiency of interior permanent magnet synchronous motors (IPMSMs) for electric vehicle (EV) compressors. Seven rotor topologies (B, dB, V, dV, D, U, and UV) were first compared, among which the U-type rotor demonstrated the highest efficiency and the lowest total loss. Subsequently, the influence of the turn number and rotor outer diameter (ROD) on the shift of the high-efficiency region was analyzed, and six key design variables were identified through Pearson correlation-based sensitivity analysis. Using these variables, a multi-objective optimization was performed in Ansys OptiSLang, which improved the integrated part load value (IPLV)-weighted efficiency from 91.05% to 92.29% and shifted the high-efficiency region closer to the main operating point. Experimental validation of the reference model confirmed the reliability of the FEM analysis, and the proposed optimal design is expected to enhance low-speed efficiency and reduce battery energy consumption in EV compressor applications.

This paper proposes a magnetic equivalent circuit (MEC)-based analytical model to rapidly predict the feasibility of achieving full magnetization during post-assembly magnetization in the mass production of interior permanent magnet synchronous motors. To account for strong magnetic saturation in both the magnetizing yoke and the rotor, the MEC is combined with a Newton–Raphson iterative scheme that continuously updates the nonlinear permeance values. The predicted magnetization state (i.e., magnetization ratio) of the permanent magnets obtained from the proposed model is evaluated and validated through comparison with finite-element method simulations.