Novel Method of Deriving Torque and Speed Curve of the Permanent Magnet Synchronous Motor Using Initial State Finite Element Analysis

This article proposes the novel method of deriving torque and speed curve (TS curve) of the permanent magnet synchronous motor (PMSM) using the initial state finite element analysis (ISF) for the purpose of reducing the high calculation cost of the repetitive finite element analysis (FEA). The ISF is a method that conducts the FEA only for the initial rotor position. As the ISF neglects other periodic parts, the calculation time for analyzing the PMSMs can be drastically reduced. To verify the performance of the proposed method, the ISF and conventional method of full period FEA (FPF) with many steps were applied to three types of the PMSMs, interior PMSM (IPMSM), surface-mounted PMSM (SPMSM), and flux switching machine (FSM). The proposed method reduces the calculation time for deriving the TS curves of the SPMSM, IPMSM, and FSM as 86.35%, 89.39%, and 89.41%, respectively, compared with conventional methods of considering the periodic parts. The analysis accuracies at the operating points of each test models are 94.24%, 99.24%, and 99.86%, and the ISF ensures acceptable accuracy considering the reduced calculation time. Therefore, the ISF can be effectively used when deriving the TS curves of the PMSMs at the early design stage of the motors.

I. Introduction

Motors are replacing conventional internal combustion engines in many applications to deal with fossil fuel crises and to reduce carbon emissions, and permanent magnet synchronous motors (PMSMs) are widely used in many fields due to their advantages such as high power and high efficiency [1]–[5]. One of the critical performances of the PMSMs is torque, and when designing the PMSMs, the required torque at the rated rotation speed should be satisfied. Whether the designed motor satisfies the operating points can be confirmed by deriving the torque and speed curve (TS curve) of the motor. However, deriving the TS curve is computationally expensive, as repetitive time-consuming finite element analysis (FEA) for each current phase angle is required. Therefore, this article proposes an initial state FEA (ISF) to derive the TS curve of the PMSMs that can reduce the analysis time and guarantees satisfactory accuracy.