Quantitative Comparisons of Outer-Rotor Permanent Magnet Machines of Different Structures/Phases for In-Wheel Electrical Vehicle Application

As one of the key components, low-speed direct-drive in-wheel machines with high compact volume and high torque density are important for the traction system of electric vehicles (EVs). This paper introduces four different types of outer-rotor permanent magnet motors for EVs, including one five-phase SPM machine, one three-phase IPM machine with V-shaped PMs, one seven-phase axial flux machine (AFM) of sandwich structure and finally one hybrid flux (radial and axial) machine with a third rotor with V-shaped PMs added to the AFM. Firstly, the design criteria and basic operation principle are compared and discussed. Then, the key properties are analyzed using the Finite Element Method (FEM). The electromagnetic properties of the four fractional slot tooth concentrated winding in-wheel motors with similar dimensions are quantitatively compared, including air-gap flux density, electromotive force, field weakening capability, torque density, losses, and fault tolerant capability. The results show that the multi-phase motors have high torque density and high fault tolerance and are suitable for direct drive applications in EVs.This research was funded by National Natural Science Foundation of China, grant number 52177052, and by the Natural Science Foundation of Shandong Province, grant number ZR2020ME207

Fault Tolerant 7-phase Hybrid Excitation Permanent Magnet Machine

This paper presents a novel 7-phase hybrid excitation permanent magnet (HEPM) machine with three rotors around one stator. Two rotors with PMs axially magnetized and the third rotor with PMs radially magnetized. Thanks to the addition of the third rotor, the inactive end-windings in the configuration with two rotors are then becoming active with a contribution to the torque with an increase of 30%. The impact of the third rotor on the torque density and on the pulsating torques is presented. The fault-tolerant characteristics of the proposed machine are also presented, which proves the interests of this machine for low speed applications

Seven-phase Axial And Radial Flux In-wheel Machine With Three Active Air Gaps

For in-wheel machine, outer rotor machines appear as a natural solution. Practically these machines are either radial-flux with one rotor or axial-flux with two rotors. The paper is proposing a machine with three outer rotors with two different polarities in order to reduce useless end-windings while keeping an acceptable thickness for the radial-flux rotor and high torque quality. This Hybrid Flux Permanent Magnet original structure (named HFPM) is possible thanks to the use of seven phases. The third rotor can be considered as an option of an initial double-rotor axial-flux machine in order to increase the torque density. First, the machine structure and the winding design are presented; then, based on 3D finite element method, comparison between the two machines, with two or three rotors, are provided in terms of torque densities and qualities

Torque Optimization of a Seven-Phase Bi-harmonic PMSM in Healthy and Degraded Mode

Compared to sinusoidal machines, a bi-harmonic machine (with only two harmonics of similar value in the electromotive force spectrum) can develop torque of comparable values under three kinds of supply: with only first or both first and third sinusoidal currents. Therefore, more degrees of freedom for the control of the machine can be achieved. In this paper, the specificities of a 7-phase bi-harmonic permanent magnet synchronous machine (PMSM) are investigated under different control strategies, such as maximum torque per ampere (MTPA) at low speed and fluxweakening strategies at high speed, both in healthy and faulty operation modes. The fault with one open-circuited phase are taken into account. The current references are calculated in order to maximize the output torque under the constraint on both voltage and current. The performances of the considered machine is validated by numerical results

Gating Mechanism of Aquaporin Z in Synthetic Bilayers and Native Membranes Revealed by Solid-State NMR Spectroscopy

Aquaporin Z (AqpZ) is an integral membrane protein that facilitates transport of water across <i>Escherichia coli</i> cells with a high rate. Previously, R189, a highly conserved residue of the selective filter of AqpZ, was proposed as a gate within the water channel on the basis of the observation of both open and closed conformations of its side chain in different monomers of an X-ray structure, and the observation of rapid switches between the two conformations in molecular dynamic simulations. However, the gating mechanism of the R189 side chain remains controversial since it is unclear whether the different conformations observed in the X-ray structure is due to different functional states or is a result of perturbation of non-native detergent environments. Herein, in native-like synthetic bilayers and native <i>E. coli</i> membranes, a number of solid-state NMR techniques are employed to examine gating mechanism of the R189 side chain of AqpZ. One R189 side-chain conformation is highly evident since only a set of peaks corresponding to the R189 side chain is observed in 2D ¹⁵N–¹³C spectra. The immobility of the R189 side chain is detected by ¹H–¹⁵N dipolar lineshapes, excluding the possibility of the rapid switches between the two side-chain conformations. High-resolution monomeric structure of AqpZ, determined by CS-Rosetta calculations using experimentally measured distance restraints related to the R189 side chain, reveals that this side chain is in an open conformation, which is further verified by its water accessibility. All the solid-state NMR experimental results, combining with water permeability essay, suggest a permanently open conformation of the R189 side chain in the synthetic bilayer and native membranes. This study provides new structural insights into the gating mechanism of aquaporins and highlights the significance of lipid bilayer environments in elucidating the molecular mechanism of membrane proteins