An Improved Rotor Cooling Structure of IPMSM

For the interior permanent magnet synchronous machine, the rotor temperature at the axial center is high because of its low axial thermal conductivity. The conventional the rotor structure with axial and radial vent holes has low air velocity in the axial center position, so the cooling performance for the rotor is unsatisfactory. In this paper, an improved rotor cooling structure is proposed by analyzing the air flow path. In order to enhance the convection in the rotor axial center, the location and distribution of axial vent holes and the radial vent holes is improved. An optimized structure is presented by analyzing the effects that the parameters of the proposed structure to the rotor temperature considering the electromagnetic performance of the motor. Compared with the conventional structure, the highest rotor temperature of the optimized structure is decreased by 7.6%, and it has little impact on the electromagnetic performance.