Design Considerations of an Outer Rotor PMSM for Ventricular Assist Devices

This study focuses on the design consideration of an embedded outer rotor Permanent Magnet Synchronous Machine (PMSM) tailored for a Ventricular Assist Device (VAD). The primary aim was to address the unique requirements of VAD systems, including compactness, efficiency, and integration without disrupting fluid flow dynamics. Key design constraints of the VAD structure were identified, and parametric swept processes were conducted with an emphasis on permanent magnet dimensions. The selected PMSM, featuring a magnet arc of 120°, magnet thickness of 1.15 mm, and back-iron thickness of 2.35 mm, meets the operational demands of 18 mNm torque at 5000 rpm. Thermal analyses, accounting for losses, revealed no significant temperature rise in the rotor part exposed to external fluid (36.5°C operating environment), confirming the thermal suitability of the PMSM for the VAD system. The design eliminates the size-increasing issues of traditional VAD stator placements and integrates seamlessly into the VAD structure without altering flow dynamics. Finite Element Method (FEM) simulations validated the machine's performance in terms of torque, efficiency, and magnetic flux density. Results demonstrate that the proposed outer rotor PMSM offers a compact, efficient, and reliable solution for VAD systems, ensuring both mechanical compatibility and enhanced patient comfort.