Electromagnetic design and comparative analysis of compact PM motors for ventricular assist devices

The performance and longevity of Ventricular Assist Devices (VADs) depend on an optimized drive system that balances energy efficiency, torque density, and spatial constraints. VADs, as battery-powered systems, require minimal energy consumption, while maximizing torque output for reliable operation. This study compares three small-scale Permanent Magnet Synchronous Machine (PMSM) topologies-Radial Flux (RFPMSM), Axial Flux (AFPMSM), and Outer Rotor (ORPMSM)-to determine the most suitable VAD drive system. Analytical modeling and 3D finite element analysis (FEA) evaluate key performance metrics, including torque production, back-EMF, efficiency, and losses. Results show that RFPMSM offers the highest torque density but increases device volume (110.4 cc); while AFPMSM is the most compact (66.4 cc) but has lower efficiency (65%). ORPMSM achieves the highest efficiency (84%) with a balanced footprint, making it ideal for compact, energy-efficient designs. An optimized RFPMSM design reduces its volume to 88.4 cc, improving feasibility for space-constrained applications. These findings emphasize that motor selection should prioritize efficiency, manufacturability, and seamless VAD integration to enhance next-generation implantable devices.