Abstract：The development trend of magnetic components is higher frequency, smaller volume, and higher power density. With the increase of power density, heat dissipation becomes a key factor affecting the reliable operation of magnetic components, which puts forward higher requirements for the thermal analysis of magnetic components. The traditional thermal analysis models have problems such as long calculation time and single heat transfer way. In addition, the thermal anisotropy, different distribution of loss density in magnetic core and interaction effect between temperature and loss are usually ignored. A precise and generalized analytical thermal modeling method is needed to meet the calculation requirements of the magnetic component optimization design and match the actual working condition with complex heat dissipation ways. The inductor made of an EE-type magnetic core is taken as an example, and the three-axis nine-thermal-resistance network model with thermal anisotropy is introduced for solving the heat conduction problem. A three-axis fifteen-thermal-resistance network model was proposed considering multiple heat transfer ways, thermoelectric coupling, material thermal anisotropy, and actual loss distribution of magnetic core. For multiple heat transfer ways, the influence of heat conduction, heat convection, and heat radiation should be considered because high-power density magnetic components are often used with water cooling, air cooling, or other cooling structures. Moreover, the influence of heat convection and heat radiation has been considered in the model as air thermal resistances. The magnetic field distribution influences the loss density distribution in each area. The loss distribution of the magnetic core is calculated by the 2D finite element simulation of the actual magnetic field to match the actual condition. The loss of winding and magnetic core requires iterative calculation because the temperature affects the magnetic core’s iron loss density and copper’s electrical conductivity. In contrast, the winding loss and magnetic core loss affect the temperature. In addition, the thermal anisotropy is considered in the model. The conduction thermal resistances of different axes in the Cartesian coordinate system are calculated by different thermal conductivities due to thermal anisotropy. At the frequency of 50 kHz, three working conditions of Vp=350 V, Vp=460 V, and Vp=590 V were selected to verify the model. The results show that the max relative error for calculating the magnetic core temperature is no more than 14%, and the max relative error in the highest temperature area of the magnetic core is no more than 6% under three working conditions. Compared with other thermal resistance network models, the precision of the thermal resistance network model can be improved by considering the material thermal anisotropy, thermoelectric coupling, and actual distribution of core loss. The single calculation time of the model can be reduced from several hours in 3D finite element simulation to almost one millisecond in the thermal resistance network. The total calculation time of the thermal resistance network model can meet the time requirement of calculating a large number of design points for optimizing a specific structure magnetic core. Based on the comprehensive thermal resistance network model, a general thermal modeling method is summarized for magnetic components composed of EE, EI, UU, and other typical magnetic cores. The thermal equivalent modeling of the air gap, edge effect, and leakage flux on flux density near the air gap can be considered in the model in the future. A more comprehensive analytical analysis of the temperature field can be carried out, and more precise temperature field calculation results can be obtained, providing a more reliable reference for the heat dissipation design of magnetic components.
郭轩, 肖云昊, 李驰, 郑泽东. 综合考虑材料热各向异性与多种传热方式的磁性元件热阻网络精准模型[J]. 电工技术学报, 2024, 39(6): 1806-1817.
Guo Xuan, Xiao Yunhao, Li Chi, Zheng Zedong. An Accurate Thermal Resistance Network Model for Magnetic Elements Considering Thermal Anisotropy of Materials and Various Heat Transfer Ways. Transactions of China Electrotechnical Society, 2024, 39(6): 1806-1817.
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