Stainless-Core Submersible Permanent Magnet Synchronous Machine

A fully submersible permanent magnet synchronous machine (PMSM) is introduced in this paper. Underwater operation requires that the machine parts have to be resistant to corrosion, and the electrically conducting parts need to be properly insulated from water. The machine under study consists of a rotor-surface permanent magnet rotor, protected by a glass-fiber-reinforced plastic (GFRP) cover, and a fully stainless stator. The novelty of the machine is found in the design and special materials used in the manufacture. The stator core is made of ferritic stainless steel laminations, and the selected winding material is polyvinyl chloride (PVC) insulated copper wire. An extra low-speed, stainless-core submersible PMSM was constructed and tested. To simplify the machine construction, a tooth-coil single-layer winding was adopted. An asymmetric stator design was selected to enhance the machine performance. The performance of the 1.7 kW, 80 r/min machine was analyzed by finite element analysis (FEA) and validated by experimental tests, where despite a very low rotational speed, 74% efficiency was reached at the target load point. The PMSM was found to be fully functional for the application.