Designing a Halbach Rotor Magnetic Gear for a Marine Hydrokinetic Generator

This article presents the electromagnetic and mechanical design as well as experimental testing results for a 9.5:1 gear ratio, series connected, coaxial magnetic gear (MG) for use in a marine hydrokinetic generator. A two- and three-dimensional magnetostatic finite-element analysis (FEA) sizing analysis was also conducted and a torque density comparison between using a nested or series MG typology is presented. To achieve a high torque density, a four-segment per pole-pair Halbach rotor assembly with a unique slotted Halbach magnet arrangement was used that enables the Halbach rotor magnets to be more easily assembled, even with dimensional tolerance inaccuracies. A deflection and thermal FEA analysis along with experimental validation test results are presented. The experimentally measured torque and torque density for the MG design are 188.4 N·m and 236.5 N·m/L, respectively.