Study of Torque Characteristics in Synchronous Motors designed by Topology Optimization

Abstract

The recent increasing demand for electrification technology development has led to vigorous motor design research. In particular, synchronous motor types are widely used and this study set it as a design target. The torque generated by conventional synchronous motors consists of permanent magnet torque using permanent magnet and reluctance torque induced by iron core geometry. Since the motor has different proper torque components depending on the driving area, it is necessary to consider the configuration of torque in the initial design. In this study, the configuration of torque was defined as the torque characteristics and a basic design was carried out to investigate various design results depending on torque characteristics. The torque characteristic of the motor is determined by the shape of the rotor. The permanent magnet torque is determined by the shape, size, and strength of the permanent magnet, and the reluctance torque is determined by the iron core shape. In this study, topology optimization was applied to the design of the rotor iron core. Topology optimization is suitable for basic design due to its high degree of freedom. Magnet shape was predetermined due to limitations in implementing multi-material optimization that considers magnet and iron simultaneously. The torque analysis was performed using the Maxwell Stress Tensor (MST) method and the D, Q-axis method based on the electromagnetic field analysis result. Topology optimization of rotor iron core was performed varying permanent magnet shapes. The torque performance analysis of the design results confirmed that the torque characteristics vary depending on the rotor shape. In the case of permanent magnet inserted in the V shape, the result with the highest average torque was obtained as the permanent magnet torque and the reluctance torque were evenly used. Furthermore, it was confirmed that the permanent magnet torque decreased linearly and the reluctance torque increased as the usage of permanent magnet decreased. In addition, topology optimization was applied to the stator to minimize the torque ripple generated by the motor operation.