Impact of the Motor Length-to-Diameter Ratio on the Selection of Cooling Water Channels for the Permanent Magnet Synchronous Motor

Aiming at the problem of difficulties in heat dissipation for a permanent magnet synchronous motor (PMSM) with high power/torque density, the effect of motor length-to-diameter ratio (r0) on the selection of cooling water channels is investigated from the perspective of the geometric parameters of the PMSM in this paper. First, the 3-D fluid-solid coupled heat transfer models of three actual motors with the length-to-diameter ratios of 0.27, 0.81 and 2.04 are established. Every model is calculated under spiral, axial and circumferential cooling water channels, respectively. The cooling effect, cooling energy loss and motor thermal balance are compared and analyzed. Then the optimal cooling water channel for each of three motors is confirmed. Further, the motor temperature rise and fluid differential pressure are plotted. The threshold of motor length-to-diameter ratios is determined at which the overall performance of the axial and circumferential cooling water channel is highly similar. The general conclusions of selection of cooling water channels for PMSMs with different geometry shape are summarized. Finally, a prototype with r0 = 0.27 is fabricated and tested, verifying the validity of the fluid-solid coupling simulation analysis. (c) 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.