Specification and Design of Ring Winding Axial Flux Motor for Rim-Driven Thruster of Ship Electric Propulsion

This paper proposes an application of a new electric motor topology named ring-winding axial flux machine (AFM) for rim-driven thruster of ship propulsion system. Ring-winding AFM has many advantages, such as reliability, simple construction, ease of increasing phase numbers, and pole numbers, which are important for marine application. In rim-driven thruster, the electric motor is fitted in the duct surrounding propeller so that electric motor and propeller are integrated into one unit. Due to this integration, the electric motor design is more affected by the design of propeller and hull. This paper presents a new method to determine electric motor specifications considering propeller and hull. Design methodology and constraints are presented for the ring-winding AFM as well. To prove the concept of the proposed topology, confirm manufacturability, and substantiate validity of three-dimensional (3-D) FEM simulations, a small-scale prototype is fabricated and tested. Furthermore, to demonstrate the effectiveness of the proposed method for determining electric motor specifications, a case study is done for Nordhavn 52 ship. Then, a ring-winding AFM is designed and its performance is evaluated with 3-D FEM simulations.