Magnetic-geared Permanent Magnet Machines Research Articles

Improved design and analysis for electromagnetic performance of magnetic geared permanent magnet machine according to winding pattern and segmentation of permanent magnet

This paper presents an analysis of the operating principle of magnetic geared permanent magnet machines (MGPMMs), electromagnetic analysis results according to the winding pattern, and a method for improving power factor and loss characteristics. To improve electromagnetic performance, the air gap magnetic flux density was calculated using the finite element method, and the harmonics of the inner and outer air gap magnetic flux densities was analyzed using the fast Fourier transform (FFT). From the FFT results, harmonic orders that affect electromagnetic performance were presented, and the electromagnetic analysis results were compared to derive correlations with torque ripple and losses. In addition, a design method for improving electromagnetic performance and operating characteristics was proposed by comparing power factors according to winding pattern. In particular, to improve the robust design and efficiency of MGPMM, a method of reducing eddy current loss by segmenting permanent magnets was addressed. The proposed analysis and design method can be widely used in the design and characteristic analysis of MGPMM.

Analysis and Design of Novel Structured High Torque Density Magnetic-Geared Permanent Magnet Machine

The main limitation of magnetic gears is their relatively low torque density. Therefore, a novel structured high torque density magnetic-geared permanent magnet (MGPM) machine, which combines the advantages of a conventional MGPM machine and magnetic gear to enhance the torque considerably and achieve low-speed high-torque operation, is proposed in this study. However, there are different structures for increasing torque of a machine. Therefore, in order to demonstrate the advantages of the proposed structure, it is compared with other structures, using the finite element method. Moreover, the proposed MGPM machine can transmit an additional 42.3% of torque density when compared with the conventional MGPM machine of the same size.

Analytical Investigation of the On-Load Electromagnetic Performance of Magnetic-Geared Permanent-Magnet Machines

In this paper, the electromagnetic performance and operating characteristics of magnetic-geared permanent-magnet machines (MGPMMs) are evaluated using the subdomain analytical method. We derive the governing equations for each region based on the electromagnetic theory and some assumptions. The undetermined coefficients of the governing equations are calculated using boundary conditions. Based on the analytical solutions, the electromagnetic performance is analyzed. The proposed analytical method is validated through the nonlinear finite-element method and an experiment. In particular, an analysis of the performance analysis of the slot combination, which is one of the design variables, suggests the increased power factor and operating range. The analytical method can be useful for the initial and optimal designs of MGPMMs.

Design Optimization and Comparative Study of Novel Magnetic-Geared Permanent Magnet Machines

This paper presents a novel magnetic-geared permanent magnet (MGPM) machine with dual-layer PM excitations, referred as dual-layer MGPM (DL-MGPM) machine. The key is to employ both the outer rotor and the modulation ring with PM-iron sequences, in which the PMs are separated by iron segments one by one, and can provide PM excitation and flux modulation simultaneously. Both the outer rotor and the modulation ring can achieve flux modulating, namely, bidirectional flux modulating, which can couple the magnetic fields excited by the two sets of PMs and armature currents effectively. The proposed DL-MGPM machine, as well as its existing counterpart which employing all the PMs on the outer rotor and referred as single-layer MGPM (SL-MGPM) machine, are optimal designed using finite element method coupled with genetic algorithm. The electromagnetic performances of the DL-MGPM machine and the SL-MGPM machine are investigated in detail and quantitatively compared. The results show that the proposed DL-MGPM machine can achieve higher torque density than the SL-MGPM machine, and is more suitable for low-speed high-torque direct-drive applications.

Parallel-path power flows in magnetic-geared permanent magnet machines with sandwiched armature stator

Due to the large torque density of magnetic gears(MGs), magnetic-geared permanent magnet machines(MGPMs) have become promising competitors in the family of direct-drive machines. According to the deployment of armature stators, MGPMs can be generally classified into three types, viz., MGPM with inner armature stator(MGPM-IAS), MGPM with outer armature stator(MGPM-OAS), and MGPM with sandwiched armature stator(MGPM-SAS). Our investigation finds out that the MGPM-SAS can achieve parallel-path power flows better than the MGPM-OAS, while the MGPM-IAS is with serial power flow paths. Therefore, the torque capability of MGPM-IAS is limited by the torque transmission capability of its integrated MG. However, the MGPM-SAS has the possibility to offer even higher output torque than its integrated MG. This paper focuses on the MGPM-SAS. And three typical MGPMs and their power flow paths are introduced; the interaction of electromagnetic fields in MGPM-SAS is analyzed; simulation calculation and experimental verification are conducted to demonstrate the validity of the theoretical analysis.

COMPARISON OF MAGNETIC-GEARED PERMANENT-MAGNET MACHINES

With the advent of magnetic gears, researchers have developed a new breed of permanent-magnet machines. These magnetic-geared permanent-magnet machines artfully incorporate the concept of magnetic gearing into the permanent-magnet machines, leading to achieve low-speed high-torque direct-drive operation. In this paper, a quantitative comparison of three viable magnetic-geared permanent-magnet machines is flrstly performed, hence revealing their key features, merits, demerits and applications. Initially, the development of the magnetic gears, including the converted topologies and fleld-modulated topologies, is reviewed. Then, three viable magnetic-geared permanent-magnet machines are identifled and discussed. Consequently, the corresponding performances are analyzed and quantitatively compared. The results and discussions form an important foundation for research in low-speed high-torque direct-drive systems.