Thermal Analysis of Small-Scale Axial Flux Permanent Magnet Synchronous Motors for LVAD Systems

This paper addresses the design and thermal analysis of Axial Flux Permanent Magnet Synchronous Machines (AFPMSMs) integrated into continuous flow left ventricular assist devices (LVADs). Allowed temperature rise limitation due to medical application was the primary motivation of this research. Thermal challenges are further elevated due to the limited volume, which increases the thermal loading of the motor. Furthermore, effective cooling of both the rotor and stator was achieved, which is an innovative aspect of this work. Within the scope of this study, the thermal aspects of AFPMSMs specifically for LVAD pumps were examined, and their validations were carried out through analytical calculations and simulation studies along with some experimental work. It was validated by the FEA that the temperature of the fluid at the LVAD pump inlet under rated load increased by only 0.04 degrees C. Therefore, the pump design presented does not pose any risks to the patient. Subsequently, to validate the design, an AFPMSM prototype was manufactured and tested in a laboratory environment. These tests showed that under the rated load, the winding temperature increase was 26.5 degrees C, and the outer case temperature increase was 15.1 degrees C. These results are consistent with both analytical and simulation results. This study demonstrated that the LVAD pump design is thermally suitable and that the established analytical equations are accurate in both simulation and experimental tests. Additionally, the novel integration of AFPMSM and pump yielded significantly higher current-carrying capacity due to the devised effective cooling mechanism.