Improvement of Thermal Equivalent Circuit Network and Prediction on Heat Characteristic of Motor by Calculation of Convection Heat Transfer Coefficient

According to miniaturization, estimation of motor temperature is necessary, and many approaches are developed. Irreversible demagnetization occurred by change of permanent magnet temperature and increase in resistance are affected by temperature increase in motor due to the losses. In this paper, the temperature of motor is calculated by applying equivalent thermal circuit network. Thermal source, thermal resistance and thermal capacitor which are components of thermal equivalent circuit network are calculated and equivalent circuit is composed considering heat transfer in motor. Especially computation for heat transfer of convection is important. The prediction of temperature in existing thermal equivalent circuit is improved by more accurate calculation of heat transfer coefficient considering components of natural convection and forced convection.