형상 비와 토크밀도 함수에 기반을 둔 영구자석 동기전동기 설계

Abstract

A synchronous motor has larger starting torque and higher efficiency compared to an induction motor. In particular, permanent magnet synchronous motor (PMSM) that uses rare earth magnet has twice the power density and 8~9% higher efficiency compared to induction motors or switched reluctance motors. Due to these reasons, the industry today is switching from system that uses DC or induction motor to system that uses PMSM. PMSM is widely used for compressor for car or home appliance and wind power generation. Even with advantages that PMSMs have, the industry requires motor with better performance. Thus many researchers are researching for methods that can improve torque, efficiency, and other performance factors for PMSM. In 1987, V. B. Honsinger suggested design method using Do3L equation. In 2010, L. J. Wu proposed design method that considers ratio of stator and rotor diameter, flux density ratio, and etc. to increase torque density. Many design methods to increase torque density and reduce copper loss has been proposed in many references. However, these design methods did not consider factors stated below. First, since voltage limit is not considered, the whether the proposed method is useful for actual use is not clear. Second, efficiency considering copper loss, iron loss and operating conditions cannot be confirmed. Third, problems could rise from temperature increase since temperature characteristics when operating is not considered. In this paper, design method to increase efficiency and temperature characteristics using torque per rotor volume (TRV), torque density (TD), and split ratio (SR) which are needed for determining the motor size is proposed. Method proposed in the paper considers the voltage limit. To calculate the terminal voltage, functions using TRV, TD, and SR as independent variables is induced for inductance, winding resistance and iron core resistance is inducted. Then inductance, winding resistance, and iron core resistance is applied to d and q axis equivalent circuit. By using this method, the TRV, TD, and SR that satisifies the voltage limit can be determined. Method proposed in this paper, since inductance, winding resistance, and iron core resistance that uses TRV, TD, and SR as independent variables is applied to d and q axis equivalent circuit, the operating condisions and efficiency considering copper loss and iron loss can be confirmed. Thus TRV, TD, and SR that increases efficiency can be determined. The proposed design method in this paper, motor temperature characteristics are considered. The temperature characteristics were confirmed by applying calculated loss according to TRV, TD, and SR, and thermal resistance that uses TRV, TD, and SR as independent variables to thermal equivalent circuit. By using these methods, TRV, TD, and SR can be determined that keeps the motor at a resonable temperature. Proposed method in this paper is judged to be useful for design and performance improvement of PMSM.