개방형 공랭식 유도전동기의 열적 모델링 및 냉각 시스템 최적 설계

Abstract

Analysis of internal flow and thermal characteristics of an open-type, air-cooled induction motor was performed; in addition, optimization of the cooling fin structure for weight reduction was performed. To accomplish these efforts, numerical approach modeling, considering electromagnetic-thermal multi-physics phenomena, and thermal network approach modeling applicable to an open cooling system, were performed. In addition, the influence of each design parameter on flow and thermal characteristics was analyzed, and multi-objective optimization was performed. For the numerical approach modeling, the heat generation rate of the motor was analyzed and non-uniform iron loss distribution was applied considering the physical and electromagnetic period. The thermal characteristics of the motor were predicted by analyzing the cooling path and temperature distribution inside the motor, and the non-dimensional air-gap discharge temperature was introduced to generalize the thermal characteristics for various operating conditions. As a result, air-gap flow dominantly influenced the thermal characteristics of the motor. For the thermal network approach modeling, a three-dimensional unit structure and temperature fitting constants were defined, and the internal region of the induction motor was divided into 36 nodes in order to suggest a thermal network topology for an electric motor with an open-type cooling structure. As a result, the influence of the heat transfer coefficient on the thermal network model was reduced, which improved the accuracy of the model. The semi-CFD optimum design procedure, which combines the advantages of the numerical and thermal network model, was introduced to reduce calculation time for optimization. The influence of the design parameters on the flow and thermal characteristics was formulated through the sensitivity analysis and parametric study, and the multi-objective optimization considering the relationships between the design parameters and flow and thermal characteristics was performed. As a result, the total mass of the cooling fins was reduced by 10% without penalties of cooling performance and pressure drop.