Design, Construction, and Analysis of a Large-Scale Inner Stator Radial Flux Magnetically Geared Generator for Wave Energy Conversion

Abstract

A magnetically geared machine (MGM) integrates a magnetic gear with a low-torque, high-speed electric machine to create a single compact high-torque, low-speed device with the size advantages of a mechanically geared system and the reliability of a direct drive machine. This work investigates the use of MGMs for wave energy conversion through the development of a large-scale magnetically decoupled inner stator radial flux magnetically geared generator rated for 10 kW at an input speed of 30 r/min. Critical design trends are illustrated using parametric two-dimensional and three-dimensional finite element simulation results. Information is also provided about the prototype's mechanical structure and key magneto-mechanical design considerations, including the impact of modulator bridges and the extent of axially escaping leakage flux. The prototype's experimental stall torque of 3870 Nm represents a 99.1% match with the simulated stall torque and corresponds to volumetric and gravimetric torque densities of 82.8 kNm/m3 and 14.5 Nm/kg, respectively. Additionally, the prototype achieves an experimental efficiency of approximately 90% for operation near rated torque.