Investigation of the heat transfer coefficient on the fins for total enclosed fan cooled permanent-magnet motor

This paper investigates the cooling fins of a 55 kW surface permanent magnet synchronous motor (PMSM). Compared with the electric machines cooled by the shaft-mounted fans, this kind of motor has different flow conditions. Therefore, the empirical formulae used to calculate the heat transfer coefficients of the fins of traditional motors are not suitable. Thus, the heat transfer coefficients of fins are analyzed based on the finite volume method by using the conjugate heat transfer approach. Furthermore, the cooling medium´s properties, such as flow velocity and streamlines in the external and internal air regions are analyzed. Experiments are carried out to verify the solution model, showing acceptable accuracy of the calculated results. Finally, the empirical formulae of the fins to calculate the heat transfer coefficients are summarized, which are helpful to design the electric machines with the same structure.