Comparative Research on Topologies of Contra-Rotating Motors for Underwater Vehicles

Underwater vehicles have been widely used in marine exploration and development. A contra-rotating propeller (CRP) can improve propulsion efficiency, eliminate the roll moment of the propeller acting on underwater vehicles, and significantly improve the dynamic performance of underwater vehicles. Contra-rotating motors (CRMs) are used to drive CRPs. Topologies of CRMs include an armature rotating contra-rotating motor (ARCRM), double contra-rotating motors (DCRMs), and a double rotor contra-rotating motor (DRCRM). In this paper, the design and optimization of these different topological CRMs were realized with analytical calculations of the magnetic field and electromagnetic performance. The efficiency map and losses analysis of CRMs with different topologies are obtained with the finite element method. In order to achieve suitable CRMs to drive the CRPs of underwater vehicles, three topologies for CRMs will be compared comprehensively from the perspective of structure, weight, size, loss, and efficiency. For low-speed, high-torque CRPs, the ARCRM has been proven to improve efficiency and power density. An ARCRM prototype was developed to verify this solution and its reliability.