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This paper investigates the influence of stator/rotor pole number combinations and permanent magnet (PM) numbers on electromagnetic performance of consequent-pole hybrid excited flux reversal machines (CP-HEFRMs), which have different numbers of PM poles and iron poles and concentrated AC and DC windings on the stator and a salient pole rotor. PMs in the slots of one stator pole are magnetized radially in the same direction, while opposite on adjacent stator poles. Magnetic field paths of DC, PM, and hybrid excitations are investigated. The phenomenon of flux cancellation, i.e., PM and DC MMFs in CP-HEFRMs are of opposite polarities in the flux-enhancing operating mode, is revealed and verified, for the first time, as the key feature that makes CP-HEFRMs different from other hybrid excited machines. Consequently, the saturation in stator pole and yoke can be mitigated and hence the overload capability of DC excitation is enhanced, which is verified by finite element analysis (FEA). Global optimizations are utilized to obtain the optimal rotor and stator pole number combinations and PM numbers for each stator pole. Torque, torque ripple, inductance, unbalanced magnetic force, and flux regulation capability are compared for different PM numbers and rotor pole numbers. Comparisons are made on consequent-pole and non-consequent-pole topologies in terms of torque capacity, flux regulation capability, and PM consumption to further illustrate the advantages of consequent-pole topology. A prototype machine is built and tested to validate the analyses. [ABSTRACT FROM AUTHOR]

Consequent-pole (CP) permanent magnet (PM) configuration suffers asymmetric electromagnetic characteristics although it saves PM usage. The CP-based stator-PM synchronous machines are investigated in this paper, with particular reference to symmetrical issues. The electromagnetic performances of the CP-based stator-PM synchronous machines are firstly evaluated. Afterwards, the rule of even order harmonics cancellation is presented for different slot/pole number combinations and winding layouts, based on which symmetrical phase flux-linkages can be obtained although the unbalanced magnetic flux naturally occurs. Moreover, based on the three-dimensional finite element analysis, the unipolar end leakage-flux caused by the asymmetric magnetic field is identified, and the risk of the shaft magnetization is revealed. Finally, a pair of prototype machines are fabricated and measured to validate the analyses. [ABSTRACT FROM AUTHOR]

Asymmetric interior permanent magnet (AIPM) rotor topologies can achieve torque enhancement in IPM synchronous machines without the increase of PM usage due to utilizing magnetic-field-shifting (MFS) effect by reducing the current angle difference between maximum PM and reluctance torque components. This paper investigates the influence of armature reaction on MFS effect in AIPM machines. A general model of IPM machines considering MFS effect is analytically developed and the AIPM and IPM machines using the same stator, rotor diameter and total PM amount are comparatively studied. It shows that the armature reaction affects the MFS effect in both AIPM and IPM machines and the influence is more significant in AIPM machine. The relationships between MFS effects in PM flux-linkage and inductance characteristics and current angles for maximum PM and reluctance torque components are revealed. It confirms that the change of current angles of torque components is due to the MFS effect in PM flux-linkage and inductance characteristics in both AIPM and IPM machines. Besides, the developed machine model considering MFS effect is verified by finite element analysis. Finally, a small-scale AIPM machine prototype is fabricated and measured to validate the finite element analysis. [ABSTRACT FROM AUTHOR]

The design rules of winding configurations and stator-pole/rotor-tooth (SP/RT) number combinations of doubly-fed flux-switching permanent magnet (DF-FSPM) machines are investigated in this paper based on coil electromotive force (EMF) vectors. The relationships between the components of stator and rotor coil-EMF vector diagrams are unveiled at first, including the numbers of stator and rotor phases, and the numbers of stator and rotor spokes. Then, the SP/RT number combinations are derived considering feasible stator/rotor phase number combinations and different winding configurations. The SP/RT number combinations are optimized considering the winding factors, magnetic field harmonics, unbalanced magnetic forces and machine diameter. It is shown that both of the stator and rotor pitch factors increase when the SP and RT numbers get closer. Furthermore, the influence of winding configurations and SP/RT number combinations on electromagnetic performances of DF-FSPM machines are analyzed by finite-element method. Finally, the analysis results are validated by experiment. [ABSTRACT FROM AUTHOR]

Axial-flux permanent magnet (AFPM) machines are gaining popularity in low-speed and high torque applications due to their high torque density, high efficiency, and compact structure. In this article, a dual-rotor slotless AFPM (DRSAFPM) machine equipped with equidirectional toroidal winding (EDTW) is proposed and compared with that equipped with conventional single-layer and double-layer concentrated windings (CWs). First, the differences between the DRSAFPM machine with EDTW and that with conventional CWs in coil layout, electromotive force (EMF), and winding magnetomotive force are revealed. Considering the special coil layout of the EDTW, the coil factor and size equations of the DRSAFPM machines with EDTW and conventional CWs are presented. Second, the electromagnetic performance including air-gap field, back-EMF, torque, and efficiency of the DRSAFPM machines with EDTW and conventional CWs are analyzed based on the three-dimensional finite-element method. The simulation results validate the correctness of the coil factor and size equations and indicate the EDTW–DRSAFPM machine has superiority in back-EMF amplitude and torque density. Finally, a prototype of the EDTW–DRSAFPM machine is manufactured and tested, which validates the feasibility of the EDTW–DRSAFPM machine and the correctness of the analysis. [ABSTRACT FROM AUTHOR]

Variable reluctance resolvers (VRRs) have been widely used for rotor position detection in harsh working conditions. However, conventional installation of VRRs inevitably occupies the axial space of machine systems, and may weaken the reliability of rotor position detection encountering shock and vibration. In this article, a novel VRR structure with inner stator is investigated, which is radially integrated inside a permanent magnet synchronous machine (PMSM) to construct compact machine topology. The hybrid machine topology is first discussed, and detailed electromagnetic design is carried out. Improved analytical analysis on air gap flux density distribution and inductance evaluation of the integrated VRR is derived based on modified winding function approach, and testified by finite element analysis. A prototype is manufactured from an existing 2.2 kW PMSM, and experiments are conducted to validate the effectiveness of proposed machine topology. [ABSTRACT FROM AUTHOR]

In this article, an axial-flux permanent-magnet (PM) Vernier machine with the triple-stator, spoke-type PM rotor, and toroidal winding wound on the innerstator is proposed. Benefited from the flux focusing spoke-type PM rotor and short end length toroidal winding, the proposed machine has a high torque density and the improved power factor. Based on the air-gap permeance function, the analytical expression of the proposed machine is derived to qualitatively analyze the machine's performance. The quasi-three-dimensional (3-D) finite element analysis (FEA) is adopted to optimize the design parameters, such as innerstator diameter, PM thickness, and slot opening width. The quasi-3-D FEA results match well with the 3-D FEA. The 3-D FEA results show the torque densities of the proposed machine reach 49.4 Nm/L and 11.4 Nm/kg, respectively, under the 232 A/cm average electrical loading. The performances, such as overload capacity, PM demagnetization, and PM and core losses, are also analyzed by 3-D FEA. The comparison with the other axial-flux PM Vernier machine is conducted, and the results reveal that the proposed machine has the great advantages of the torque density and power factor. Since the prototype is not built, in this article, the assembly scheme and thermal behavior of the proposed machine are discussed. [ABSTRACT FROM AUTHOR]

This article proposes a consequent-pole unequal Halbach vernier wheel motor (CPUHVWM), which effectively reduces the self-flux leakage between permanent magnets, and an optimization method is proposed to improve the motor optimization efficiency and shorten the optimization time. The key variables are selected by the sensitivity analysis, and a polynomial function suitable for the optimization algorithm is constructed based on the response surface method. Based on the particle swarm optimization algorithm, the weights of different particle search areas are assigned to improve the overall optimization efficiency of the algorithm. Furthermore, to verify the superiority of the performance of the proposed structure and the applicability of the algorithm, the other two similar motor structures are compared, and the algorithm is adopted for the optimization. The optimized electromagnetic characteristics are compared by the finite element method. Finally, the prototype with the optimal parameters is built, and the effectiveness and advantages of the optimization algorithm are verified by experiments. [ABSTRACT FROM AUTHOR]

Permanent magnet synchronous motors (PMSMs) with nonconcentric magnetic poles (NCMP) structure are widely used as high-precision servo motors. The current subdomain method mainly equates the NCMP to a rectangular magnet to make each subdomain boundaries of magnet parallel when calculating the magnet eddy current loss (ECL), which results in a lower accuracy of the calculation. This article divides the NCMP into nonconcentric region and concentric region along the radial direction. The nonconcentric region is further divided along the circumferential direction, and each divided region has a single thickness. Based on the subdomain method, a novel analytical method of magnet ECL in PMSMs with NCMPs is proposed. Moreover, the three-dimensional distribution coefficient of ECL in the NCMP is derived by the equivalent impedance method. The effects of eddy current reaction and stator slotting are taken into account to improve the calculation accuracy. Then, through theoretical derivation, the relationship between the minimum magnet loss and the pole parameters is obtained, which provides a reference for the design of NCMPs. Finally, the loss separation experiment is performed on four prototypes with NCMPs. The experimental results, finite element method results and analytical results are compared to verify the correctness of the model. [ABSTRACT FROM AUTHOR]

In order to enhance motor torque performance of existing two-phase 8/10 E-Core SRM, an improved modular permanent magnet (PM)-assisted Switched Reluctance Motor (SRM) structure is presented. Firstly, basic structure and operation principle of the proposed structure are introduced. To further evaluate performance improvement, effects of various parameters on the design such as inductance, flux-linkage, average torque and cogging torque are compressively investigated by finite element method (FEM) software subsequently. In the meantime, comparisons with other two-phase SRM structures are also performed including average torque, torque/PM volume, torque/ motor volume, torque/current, etc. Finally, a prototype is fabricated, and simulation and experimental results verify that the proposed design has high torque performance. [ABSTRACT FROM AUTHOR]

A dual-stator Vernier permanent magnet (DSVPM) machine is proposed in this article for improving the power factor. Compared with the conventional single-stator Vernier permanent magnet (SSVPM) machine with the surface-mounted permanent magnet rotor, the proposed DSVPM machine has the higher power factor and the overload capacity. The reason for the higher power factor and the overload capacity in DSVPM machines is explained theoretically in this article by air gap permeance theory, and the advantages of the power factor and overload capacity of DSVPM machine are verified by the finite element analysis (FEA) through 18-slots and 34-poles SSVPM and DSVPM FEA model. The rotor eddy current losses, core losses and magnet demagnetization ratio of the DSVPM and SSVPM machines are also studied in this article, the FEA results reveal eddy current and core losses and magnet demagnetization ratio are all lower in the proposed DSVPM machine. The power factor of DSVPM machine variation with the magnet thickness and pole ratio (the ratio of the rotor pole pair number to the stator pole pair number) is also researched by the theoretical and FEA methods. In this article, a surface-mounted permanent magnet machine with fractional-slot concentrated-winding is designed to compare the torque density and cost with DSVPM machine. The sandwiched rotor structure of the proposed DSVPM machine is discussed and the structural analysis by three-dimensional FEA is carried out to prove the feasibility of rotor support, the result reveal that the rotor structure has the sufficient strength. [ABSTRACT FROM AUTHOR]

In this article, two double flux modulation permanent-magnet machines (DFMPMs) with PMs on both stator and rotor are introduced. The two DFMPMs share a similar operation principle. However, due to the different stator-PM arrangements, the two DFMPMs show different performances. In order to analyze their performance characteristics, their analytical models are built and verified by finite element analysis (FEA). Moreover, to quantitatively compare their electromagnetic performances more accurately, the two DFMPM topologies are optimized, respectively, and compared in terms of back-EMF, cogging torque,rated torque, torque ripple, power factor, and efficiency. Finally, the DFMPM topology with relatively better performances is built and tested. The experimental results match well with the FEA simulations. [ABSTRACT FROM AUTHOR]