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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]

In this paper, an analytical method (AM) based on the air-gap magnetomotive force (MMF) permeance model is proposed to predict the nonlinear instantaneous torque of switched reluctance machines (SRMs). The analytical expression of the air-gap MMF is first obtained from the winding function and current profile, while the air-gap magnetic permeance considering the double-sided slotting effects is also derived. Then, the nonsaturated field distribution along the air-gap circumference is presented based on which the instantaneous torque can be calculated from the Lorentz force law. Furthermore, the model is enhanced with a saturation distribution factor to include the nonlinear characteristics. The proposed method is free from preliminary data or empirical coefficient and benefits from the simplified model and solution. The AM will be validated by the two-dimensional finite-element method based on four SRMs with different structures. Moreover, an SRM prototype is manufactured for experimental verification. [ABSTRACT FROM AUTHOR]

The even order harmonics of the flux linkage naturally exist in every armature coil of stator-permanent magnet (PM) machines, while it is usually a basic requirement to have the symmetrical phase flux linkage free from even order harmonics. Thus, the specific harmonics must be eliminated after the coil connection. In this article, the general mechanism of the even order harmonics elimination in various stator-PM machines is investigated, and it is found that either the opposite PM polarities or the opposite coil polarities of the two adjacent phase coils can guarantee the elimination effect, and hence, the symmetrical phase flux linkages. This principle can be applied to both bipolar flux and unipolar flux machines. The analysis is validated by finite-element method and the test results of the prototype machine. [ABSTRACT FROM AUTHOR]

Hybrid excited (HE) machines have the synergies of high torque density and high efficiency of permanent magnet (PM) machines and excellent flux controllability of wound-field machines. The PMs and field coils (FCs) coexist in HE machines to provide excitations simultaneously, and can be coupled either in series or parallel. The topologies of HE machines are very diverse, which bring challenges in the selection and design of HE machines. Based on the partitioned stator (PS) platform, a pair of series and parallel HE machines having similar structures and PM usage are evaluated and compared to identify their merits and demerits. With the help of finite element analysis, the flux regulation, energy conversion capability, parasitic effects and irreversible demagnetization of the two kinds of the HE machines are comprehensively investigated and the guidance to the machine design is provided. A pair of prototypes are fabricated and tested to validate the analyses. [ABSTRACT FROM AUTHOR]

The torque production mechanism of switched reluctance machines (SRMs) is investigated from the perspective of air-gap field modulation principle. The unipolar stator current excitations can be divided into DC and AC components and they induce the air-gap magneto-motive force (MMF) respectively. Meanwhile, thanks to the salient structure in SRMs, the air-gap MMFs induced by the two sources above can be modulated to obtain the synchronized air-gap fields for torque production. It is revealed that a multitude of field harmonics contribute to the torque together. The MMF-permeance model is built and the analytical deduction of the field modulation effect is provided, with which the orders of the field harmonics contributing to the torque output can be identified. Moreover, finite element method is employed to verify the predictions on various SRM topologies. Finally, aprototype machine is fabricated and measuredfor validation. [ABSTRACT FROM AUTHOR]

Hybrid permanent-magnet (PM) variable-flux memory (VFM) machines employ both high coercive force PM, i.e., the constant PM (CPM), and low coercive force PM, i.e., the variable PM (VPM). The high energy-product CPM guarantees the benefits of high torque density of the conventional PM machines, while the PM magnetization state of the VPM is flexibly regulated to match various operation requirements. In fact, the two kinds of PMs can be magnetically connected in either parallel or series, with which the machine characteristics are quite different. In this paper, based on the two-dimensional and three-dimensional finite-element analyses, a pair of VFM machines with parallel and series connections, respectively, are investigated with specific reference to identify their difference in end effects. The comparison results show that the series hybrid PM VFM machine suffers more serious end leakage flux. The prototype machines are manufactured and tested to validate the analyses and predictions. [ABSTRACT FROM AUTHOR]

This paper proposes a novel variable flux memory (VFM) machine, in which the “constant” permanent magnet (CPM) with high coercive force and the “variable” PM (VPM) with low coercive force are alternatively located in the interior-PM rotor. Thus, the VPMs and CPMs are magnetically connected in series, with which the CPMs can assist the VPMs to withstand the unintentional demagnetization caused by armature reaction. Therefore, a high armature current can be applied to the machine. Meanwhile, the reluctance torque is retrieved. Thus, a high torque density can be obtained. Based on two-dimensional finite element analysis, first, the electromagnetic performance of the proposed VFM machine in two extreme magnetization states is evaluated in detail. Then, the demagnetization and remagnetization characteristics are investigated, in which the working points of VPMs are illustrated. Furthermore, the advantages of improved efficiency of the proposed VFM machine are demonstrated. A prototype machine is manufactured and tested to validate the predictions. [ABSTRACT FROM AUTHOR]

Switched reluctance machines (SRMs) are becoming increasingly attractive due to their inherent advantages, such as robust and rare-earth-permanent magnet-free topology, as well as excellent fault-tolerance and temperature management. However, the accurate and efficient analyses of SRMs are always challenging since they operate with variable reluctance and pulsating excitation, suffering severe nonlinear characteristics. This paper first introduces a general power equation of SRMs, which can be a powerful tool in the investigation of SRMs. Then, the proposed power equation is validated by finite element (FE) results and experimental results with different excitations. Afterwards, the calculated results with various conditions including different stator inner diameters and different stator outer diameters are compared with the FE-predicted results. Finally, the comparison between SRMs and several conventional machines is carried out to evaluate the power density of SRMs. [ABSTRACT FROM AUTHOR]

A dual-stator hybrid-excited switched-flux (DS-HESF) machine, which is based on the conventional SF permanent magnet machine but employs a secondary stator to accommodate the field windings, is proposed in this paper. The DS-HESF machine inherits the robust rotor and benefits from a better space utilization. The topology and operating principle of the proposed machine are introduced in detail. Based on the 2-D finite-element analysis, the comparison between the DS-HESF machines having different rotor pole numbers is carried out, accompanied with a conventional HESF machine as a baseline. The results reveal that the DS-HESF machines exhibit not only higher torque density but also a better flux regulation capability. The prototype is manufactured and tested to validate the predictions. [ABSTRACT FROM PUBLISHER]

The half-teeth-wound switched reluctance machines (HT-SRMs) having single-layer concentrated windings, feature simpler structures since the coil number is half, and phase-to-phase insulations in slot are eliminated. To evaluate the effects of winding configurations, the electromagnetic performances of HT-SRMs and conventional full-teeth-wound SRMs (FT-SRMs), including air-gap flux density, coil and phase flux linkage, inductance, torque, volt–ampere, and radial magnetic force (RMF), are comprehensively compared. The results based on theoretical analysis and finite-element (FE) method reveal that HT-SRMs would exhibit higher torque per ampere when the magnetic saturations are not too severe, whereas require higher voltage supply and generate more significant RMF. Further, it is found that the fault-tolerant capabilities of HT-SRMs are superior to FT-SRMs. A pair of prototypes with identical laminations but different winding configurations are manufactured and the experimental results confirm the predictions. [ABSTRACT FROM PUBLISHER]

Switched reluctance machines (SRMs) have been comprehensively researched, and they play an important role in the modern industrial field. The topology of SRMs is quite simple and only one set of windings is employed. Consequently, the winding configuration has an essential impact on performance. In this paper, a new winding configuration for SRMs with only half-teeth wound (HT-SRM) is proposed, which is totally different from the conventional SRMs with full-teeth wound (FT-SRM). First, the basic topology and operating principle of HT-SRMs are presented by a three-phase 12/8 prototype. Then, based on the 2-D finite element analysis, an optimization of the original 12/8 HT-SRM is conducted and a series of static characteristics of three SRMs, namely, a conventional 12/8 FT-SRM, an original 12/8 HT-SRM with the same iron laminations, and an optimal HT-SRM with the optimized dimensions, are compared. Finally, three 12/8 SRM prototypes are fabricated and the experimental results verify the theoretical analysis and the corresponding finite element analysis-based predictions. [ABSTRACT FROM AUTHOR]

The switched reluctance machine (SRM) has attracted increasing attentions in recent years due to its inherent simplicity, robustness, reliability and high starting torque. Meanwhile, with the aggravation of the energy dilemma and environment contamination, the research on electric vehicles is becoming the focus in a large number of counties. In China, the study on electric bicycle, which possesses high performance-price ratio and suits characteristic conditions, absolutely contains remarkable values. Here, an in-wheel three-phase 12/16 SRM-based drive system is investigated for electric bicycle. Firstly, the structure of the SRM is discussed and the prototype is designed based on finite element analysis. Then, the detailed design process of SRM is described. Also, the influence of winding configuration on the electromagnetic performance is discussed. Finally, a 350 W prototype is manufactured and the experimental test is conducted based on an ARM-based controller. The measured results verify the performance of the SRM. [ABSTRACT FROM AUTHOR]