Simple Size Determination of Permanent-Magnet Synchronous Machines

Abstract

Today, performance improvements such as reducing the time response and enhancing the efficiency of the electrical motor are one of the most important challenges. In the design of a permanent-magnet (PM) motor, the variables for sizing include the shape ratio (SR), the torque per rotor volume (TRV), and the torque density (TD), and these variables are important for determining the mechanical and electrical characteristics of the motor. This study investigated the changing patterns of the motor parameters (back electromotive force, inductance, resistance, etc.) and the motor characteristics with the changes in the SR, TRV, and TD with respect to the PM synchronous motor, and sought to determine the SR and TRV values. Toward these ends, this study proceeded with the initial design of the spoke-type (flux-concentrated) PM motor. Then, the motor parameters of the initial model were calculated using finite-element analysis. Based on the motor parameters of the initial model, the changing patterns of the electrical and mechanical characteristics of the motor according to the changes in the SR, TRV, and TD were investigated. In addition, the SR, TRV, or split ratio that can enhance the mechanical characteristics and efficiency of the motor were determined and reflected in the design.