Comparative Study of Axial Flux Magnetically Geared Machine with Conventional Axial Flux YASA Machine

Abstract

Magnetic gears (MGs) have recently been proposed to replace conventional mechanical gears in various electromechanical systems. MGs have competitive torque transmission capability compared with their mechanical counterpart[1]. Moreover, by integrating an MG into a conventional PM machine, a magnetically geared machine has emerged, greatly broadening the machine topology. It always has the merits of high torque density and reduced overall size in comparison with conventional PM machine axially combined with MGs[2]. In general, the same as conventional machines, magnetically geared machines can be considered by their flux orientations, i.e. radial and axial flux machines. Axial flux permanent magnet (AFPM) machines have unique advantages over radial flux PM (RFPM) machines, such as high torque density, low rotor losses, and high efficiency. Among various AFPM machines, the yokeless and segmented armature (YASA) machine has shown to exhibit superior performance. The machine has a unique design in which the stator is formed by separated segments with windings, and moreover, two identical surface mounted PM rotors are axially located on both stator sides[3]. Based on YASA machine, a new axial flux magnetically geared machine for power split applications has been presented in[4]. The presented machine essentially has the same stator structure as the conventional YASA machine. However, by employing different rotor pole pairs in the YASA machine, a new axial flux magnetically geared machine can be created. In this study, the axial flux magnetically geared machine and the conventional YASA machine with the same volume will be comparatively studied. Individual optimizations have been carried out to maximize the average torque of two machines. Moreover, the machine performance at no load and on load will be compared.