Topologies and performance study of a variety of coaxial magnetic gears

Abstract

This study aims to provide a comprehensive study of various magnetic gears (MGs) with simple coaxial radial flux structure. A total of 15 topologies are first introduced, by either using various rotor structures or adding extra permanent magnets (PMs) on the magnetic modulation ring. Then, all topologies with ferrite magnets are parametrically optimised, aiming to compare and evaluate the performance of these MGs. The results show that the proposed MGs with dual consequent-pole PM rotors exhibit a higher torque density than the conventional coaxial MG. Therefore, magnetic field distribution, torque-angle characteristic and on-load torque performance of these promising MGs are analysed in detail, revealing their inherent superiorities. In addition, influence of magnet material on the MG performance are investigated with emphasis on the torque density and cost effectiveness. Finally, two MG prototypes are fabricated and tested to validate the analysis.

Preliminary analysis of eddy current and iron loss in magnetic gear in electric vehicle

“…The minus sign indicates that the rotational direction between the two rotors is opposite to each other. The gear ratio for torque multiplier can be written as (6):…”

“…This structure can serve as torque multiplier or speed multiplier gear [5]. Several studies were published concerning the torque density in magnetic gear through magnetization pattern and direction of rare earth permanent magnet [6]- [8]. However, the inclusion of high energy density permanent magnet in the structure would result in a high loss in eddy current [9], [10].…”

Recent developments and comparative study of magnetically geared machines

“…Many studies have been conducted to further improve the performance of the MG: (a) for high/low-speed element, apart from the surface-mounted PM (SPM) rotor structure, other structures can be used to improve the torque density or reduce the PM volume [16][17][18][19], such as consequent-pole PM (CPM), interior-PM (IPM), pure reluctance, and Halbach PM rotor, etc. as shown in Fig.…”

Analysis and experimental verification of a novel field modulated permanent magnet gear machine

“…Following sustained research in the past few decades, various FMPMG topologies, such as axial and flux focusing configurations [5], Halbach magnet arrays [6], dual‐flux‐modulator configurations [7], and FMPMG using a stationary permanent magnet (PM) ring [8], were derived. In addition, a total of 15 FMPMG topologies with simple coaxial radial flux structures were investigated in [9]. However, speed‐change transmission in industrial applications usually increases the weight/size and cost of employing an electrical machine together with a PM gearbox.…”