Topology Optimization of Electromechanical Device for Improving Thermal Performance

Abstract

Recently, electromechanical devices such as electric motors, magnetic actuators, and inductors are being applied to various applications such as automobiles, drones and industrial robots due to fluctuation in crude oil prices, global warming, and development of battery technology. In the field automobiles, Electric motors are used in electric vehicles and hybrid vehicles with an emphasis on environmental friendliness. In the field industrial robots, magnetic actuators are used to drive robots. Also, the use of electromechanical devices in a variety of applications such as airplanes and medical devices is expanding. To be used in such a variety of applications, electromechanical devices are required to have high efficiency, high output, and miniaturization. However, miniaturization of a high-output, high-efficiency electromechanical devices causes problems such as deterioration of performance and failure due to the generation of high heat. Therefore, various studies for improving the thermal performance of the electromechanical devices have been carried out to solve the heat problem. Two aspects of heat generation and cooling can be described when improving the thermal performance of electromechanical devices. Heat generation is caused by losses of the electromechanical devices and increases the temperature of the electromechanical devices. Losses of electromechanical devices consist of coil loss and iron loss. Losses are determined by the iron and coil structure in electromechanical devices. Therefore, the amount of heat generation is determined by iron and coil structure. Cooling is a phenomenon that causes heat transfer to radiation, heat conduction, and heat convection to lower the temperature. In electromechanical devices, high temperature is prevented by using cooling-fins and cooling-channel method. The cooling is conducted by cooling-fins outside the iron part and cooling-channels inside the iron part in electromechanical devices. The iron structure has been complicated by cooling-fins and cooling channels. Accordingly, design of iron structure is critical to determining the thermal performance. And structural design method that can optimize thermal performance is necessary. In this paper, a topology optimization study was carried out to improve the thermal performance of an inductor, which is used for various applications. In this paper, topology optimization of magnetic and thermal coupled problem is conducted to design the iron part of electromechanical devices. The finite element method is adopted to calculate equations of magnetic energy, losses, and heat compliance. The material interpolation scheme was introduced to control the material property by design variables. The side-surface heat convection coefficient formulation was applied to maximize the heat convection coefficient at the interface design. And Design dependent heat generation load was expressed as a function of design variables. Therefore, the heat generation by eddy current loss can change in response to shape changes for topology optimization of an iron part in electromechanical devices. The proposed method was applied to an inductor as an example. The Globally Convergent Method of Moving Asymptotes (GCMMA) algorithm is applied as the optimization algorithm. This paper will be useful for design to improve the thermal performance of the electric motors and will help to design other electromechanical devices.