A Multi-Physics Design Approach for Electromagnetic and Stress Performance Improvement in an Interior Permanent Magnet Motor

Electric motors constitute a critical component of an electric vehicle powertrain. An improved motor design can help improve the overall performance of the drivetrain of an electric vehicle making it more compact and power dense. In this article, the electromagnetic torque output of a double V-shaped traction IPMSM is maximized by geometry optimization, while considering overall material cost minimization as the second objective. A robust and flexible parametric model of the IPMSM is developed in ANSYS Maxwell 2D. Various parameters are defined in the rotor and stator geometries to perform an effective multi-objective parametric design optimization. Advanced sensitivity analysis, surrogate modeling, and optimization capabilities of ANSYS optiSlang software are leveraged in the optimization. Furthermore, a demagnetization analysis is performed to evaluate the robustness of the optimized design. At high-speed operation, a rotor core is usually subject to higher deformation due to the high centrifugal force. Thus, rotor stresses are reduced in the optimized design by shaping the flux barriers around the permanent magnets. This enables high structural integrity of the optimized design for high-speed operation along with the improved electromagnetic performance. The multi-physics design approach proposed in this article provides the capability to design and optimize an IPMSM geometry for performance and cost, which are essential objectives to achieve in an electrified powertrain development. Moreover, consideration of rotor stress at high operating speeds extends the applicability of the proposed design approach to high-power, high-speed electric propulsion applications.