Design and Optimization of a Magnetic-Geared Direct-Drive Machine with V-shaped Permanent Magnets for Ship Propulsion

This paper presents a novel magnetic-geared direct-drive machine (MGDM) with V-shaped permanent magnets (PMs) installed on its rotor. By extending the inner rotor shaft and connecting it to a prime motor, the torque and power density of the proposed MGDM is boosted. Additionally, compared with the conventional MGDM with surface-mounted PMs, the proposed MGDM with V-shaped PMs has a more robust rotor structure to cope with extreme operating conditions. The operating principle and structure requirement of this MGDM are first derived. Then, the geometrical parameters are optimized via a three-stage multi-objective optimization method to maximize output torque and efficiency and minimize torque ripple via the genetic algorithm and finite element analysis (FEA) combined optimization strategy. Furthermore, the proposed MGDM is artfully integrated into hybrid electric ships (HESs) to construct an onboard integrated power system (OB-IPS). Since the proposed system possesses various operating modes to cope with practical operating conditions, it enjoys a high systematic efficiency and good dynamic performance. Finally, a prototype is fabricated and tested with various operating modes by referring to the practical navigation cycle of a HES. The experimental results validate the feasibility of the proposed MGDM for being applied in HESs.