Multi-three-phase propulsion system for fault-tolerant naval rim-driven propeller

Multi-phase machines are gaining popularity especially in the field of transportation electrification. Multi-three-phase machines used in conjunction with modular three-phase converters result in a redundant structure with the great advantage of fault-tolerance operation capability. The present work reports the study of a multi-three-phase machine for a rim-driven propeller pod, to be employed in yachting boat electrification. The design of the machine, i.e. annular construction with large hollow shaft, was chosen to satisfy the constraints for the integration into the existing propulsion pod and to meet the reference nominal torque and speed for the inner propeller design. Detailed simulation of losses, including the effect of PWM modulation, was performed to assess the machine losses and to define the optimal switching frequency suitable for the drive. The study then focused on the fault operation capability by calculating the radial force acting on the machine rotor under different fault scenarios.