Thermal analysis of high speed permanent magnet brushless DC motor

In order to solve the problems of reduction in magnetic performance and winding insulation damage caused by high temperature in high speed permanent magnet brushless DC motor, a series of research on temperature distribution and improvement was carried out. The thermal network mathematic model was established by lumped parameters method. And an analytic equation accounting for the relationship among motor loss, thermal conductance and temperature was derived. Besides, the motor 3D finite element model was built based on the ANSYS/Workbench, and steady-state analysis was conducted. The temperature distribution of the whole motor was achieved, which verified the results of thermal network model. And two methods including changing the retaining sleeve material and drilling holes on shaft were proposed to solve the temperature problem. According to the analysis results the rotor temperature has dropped obviously, especially the retaining sleeve and permanent magnet with a temperature decrease of about 34°C and 54°C respectively.