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Multiphase machines with a prime number of phases (five and seven) have shown better torque density than machines with other phase numbers. Unfortunately, these machines require a special stator design. Hence, this paper proposes general rewinding techniques to obtain a five-phase winding from the existing standard three-phase stator frames. The proposed rewinding techniques are applied to construct a five-phase star-connected synchronous reluctance machine (SynRM 1) and a novel combined star-pentagon winding (SynRM 2). Simple mathematical formulations are introduced to compute the equivalent winding factor. The performance of five-phase SynRMs is analyzed using 2D Ansys Maxwell transient simulations under the same copper volume for both healthy and faulty cases. SynRM 1 and 2 provide 6.56% and 13.35% higher torque compared to the three-phase SynRM at rated current and at optimal current angle. The torque ripple is decreased by 17% and 30% respectively. Moreover, SynRM 1 and 2 offer a better performance at the faulty case; e.g. at one phase opened, the average torque of SynRM 1 and 2 is 82% and 108% higher compared to the three-phase SynRM. In addition, the torque ripple is reduced by about 63% and 81%. Finally, experimental results are done to validate the proposed winding techniques.

This article presents a novel permanent magnet assisted flux-controllable machine, namely the hybrid-excited biased-flux machine (HEBFM). The proposed machine can implement flexible flux regulations (i.e., either field weakening or strengthening) by integrating the field current winding with the half consequence permanent magnet (PM) poles in the stator. The topology of the HEBFM can be explored to multi-pole cases, which contributes to improved flexibility for the flux control and winding regulation. Compared to the conventional flux-controllable machines, the proposed machine gains the merits of owning (i) extended flux control range via the modulation of winding factor (i.e., winding factor modulation), (ii) stable and compact structure and (iii) reduced demagnetization risk of permanent magnetics (PMs), (iv) capability of topology exploration. In this paper, operation principle and electromagnetic performance of the proposed machine is analyzed using the finite element method (FEM). Besides, the torque and torque ripple are optimized based on the multi-objective differential evolution (DE) coupled with FEM. Finally, a prototype is manufactured and tested to validate the effectiveness and feasibility of the proposed machine designs.

This paper aims to investigate and reveal the torque enhancement mechanism in several emerging switched flux permanent magnet (SFPM) machines by employing a unified torque equation with an improved winding factor function. Based on a hybrid finite-element (FE)/analytical method, the torque contributions of the major air-gap field harmonics in the conventional, C-core and E-core, and consequent-pole (CP) SFPM machines are identified and quantified by taking a conventional 12-stator-slot/13-rotor-tooth (12s13r) SFPM machine as a benchmark, which shows that the dominant torque proportions are contributed by the low-order field harmonics due to the amplification effect of the gear ratio. Besides, a low-order field harmonic impeding effect is observed in the conventional and C-core SFPM structures, resulting in a compromised torque capability. Whereas, since the auxiliary teeth and stator iron bridge designs provide relatively lower magnetic reluctances for low-order harmonics, the E-core and CP structures can produce improved the low-order harmonics and higher torques than the conventional one. Finally, some experiments on a CP-SFPM machine are conducted to validate the theoretical and FE analyses.

This paper formulates the difference in base frequency and maximum torque between distributed and concentrated windings taking into account the air-gap modulation of concentrated-winding permanent magnet (PM) motors. The design superiority is typically confirmed for each winding type during a development period by using time-consuming finite element analysis (FEA). We propose a quantification that enables motor designers to easily judge, at the initial design stage, a superior winding type and to shorten a design period. Throughout our formulation, we found that the distributed-winding PM motors, in principle, have larger q-axis inductance and smaller d-axis inductance than the concentrated-winding motors, which leads to a decrease in the base frequency. On the other hand, the distributed winding inherently has higher winding factor and needs shorter stack length of core than the concentrated winding for identical torque output, which results in an increase in the base frequency. And also, we theoretically quantified the difference in reluctance-torque contribution between the two winding types and found that it was too small to have much impact on practical design. We applied the proposed formulae to a 0.2-kW concentrated-winding motor.The FEA and measurement results demonstrated the validity of the proposed approach for the fabricated distributed-winding motor.

For the advantages of oriented silicon steel sheet (OSSS) with better magnetic permeability in the rolling direction, this paper proposes a permanent magnet (PM) torque motor with armature teeth made by OSSS. This paper introduces the influence of unequal tooth width on the winding factor and the width calculation method of the armature teeth tip top, and analyzes the torque performance improvement by OSSS. In the end, based on testing the B-H waves of OSSS, the flux linkage, back electromotive force, rated torque and overload torque of three motors with different structure or material are compared by finite element software. The results show the proposed motor can increase the torque density and overload ability.

Automotive starter-generator applications require a high peak torque for cranking and a wide speed flux weakening region for generation. In such applications, the pole-changing winding induction machine offers a wide speed flux weakening region with a low pole number and a high peak torque capability when operated with a higher number of poles. In this article, a 6-phase, electronic pole-changing winding induction machine with improved performance over the existing 3-phase pole-changing is discussed. Compared to the 3-phase 120o phase belt winding, the proposed 6-phase pole-changing winding induction machine shows a 15 % increase in peak torque due to improved winding factor. Finite element analysis is used to predict the torque capability, losses and efficiency of the 6-phase and 3-phase pole-changing winding induction machines. A 1kW induction machine is prototyped and the improved torque capability of the 6-phase pole-changing machines over 3-phase counterparts is experimentally validated under various operating conditions.

Low-power machines were commonly considered as the main application field of concentrated windings. However, a lot of paper have recently been published, which address both the theory of these windings and specific cases of their application for large synchronous machines. The article presents an analysis of the parameters of concentrated windings having various configurations intended for use in high-power gear and gearless wind generators. In assessing the winding, not only the high winding factor value was taken into account, but also the star of slot EMFs, harmonic spectra of the MMFs and EMFs, the cogging torque component and torque pulsation under load, as well as emerging losses. It is shown that the well-known advantages of concentrated windings over distributed windings can be fully realized by choosing the appropriated numbers of slots and poles.

In this paper, the dual-stator axial-field flux-switching permanent magnet (DSAFFSPM) motors with E- and U-core stator modular segments, as well as different stator/rotor-pole combinations are compared. The operation performance of the DSAFFSPM machines are explored by using the MMF-permeance model method. A more comprehensive theoretical analysis, no more limited to numerical calculation, is presented. This reveals directly the relations between the operation performance and design parameters of the machine. The performance comparisons between the E-shaped and U-shaped teeth DSAFFSPM machines are given, including the effects of the structural parameters on the electromagnetic torque, different stator/rotor-pole combinations on the winding factor and gear ratio, the differences of the average torque and the torque density and the efficiency in the 12/10 U-core and 6/10 E-core topology. These are the basis of the DSAFFSPM machine design and optimization. Finally, the experiments on the two prototype, 6/10 E-core and 12/10 U-core DSAFFSPM machines are carried out. The results show that the average torque of the 12/10 U-core prototype is higher than that of the 6/10 E-core prototype, while the torque density and the efficiency of 6/10 E-core DSAFFSPM machines are much higher.

Refurbishing electrical machines to have a higher performance and/or reliability is a clear trend in the circular economy. This paper investigates the gain in efficiency, torque density and reliability with replacing the windings and the iron of the stator of existing three-phase synchronous reluctance machines (SynRMs), resulting in a multiphase machine. The stator housing, shaft, bearings and the rotor are not changed, to keep the cost of refurbishing low. As the housing and rotor are kept, logical constraints are to have the same inner and/or outer stator diameters, air gap length and axial length. In the new windings, an identical copper volume is considered as a constraint. An optimization technique is coupled to 2D finite element method to select the optimal slot dimensions. Case studies showed that it is possible to replace the stator of existing three-phase SynRMs with a better performance multiphase one. It is found that the average torque, efficiency and power factor of the five-phase SynRM are increased by 11.78%, 0.72% and 5.54%, respectively, compared to a three-phase SynRM at rated conditions. At higher speeds (three times rated value), the efficiency and average torque are greatly improved by about 3.64% and 33.67%, respectively, compared to the three-phase SynRM. Moreover, a faulty case of one phase opened is also investigated. The five-phase SynRM works at 75.45% of the healthy rated torque of the three-phase SynRM, whereas the three-phase SynRM works at only 43%. Measurements on an existing 5.5-kW, three-phase SynRM confirm the observed results.

Due to the elimination of the magnetic core on the stator, the design of coils is more flexible and more sensitive to the number of rotor poles for ironless stator axial flux permanent magnet (AFPM) machine. The slot-pole combination is a vital aspect of optimization design for the improvement of torque and power density. This article is mainly aimed at investigating the influence of slot-pole combination on the comprehensive performance of ironless stator AFPM machine with non-overlapping concentrated windings. Firstly, the space utilization of coils and winding factor of non-overlapping concentrated winding are deduced in formula form to compare the output capacity. And the copper mass and utilization are analyzed with different numbers of slots and stator diameter. Then, field utilization ratio is defined and derived to analyze magnetic flux leakage of Halbach-array PM dual-rotor for different numbers of poles. The performance comparison of the optimized prototypes is carried out using three-dimensional finite element analysis (3-D FEA). The back-EMF, torque and winding loss are also highlighted. Finally, a 50 kW prototype with 12-slot and 10-pole is designed and manufactured for experimental validations. This paper provides a valuable reference to select the basic configuration for the ironless stator AFPM machine application.

This paper analyses the performance of synchronous reluctance motors (SynRMs) when an existing three-phase stator is rewound to a higher number of phases. The introduced rewinding technique offers an optimized distribution for air gap flux, higher winding factor and higher value for the fundamental component of the magneto-motive force with lower harmonics. The number of turns of the proposed multiphase winding is calculated, keeping fixed copper volume. Finite element simulations verified that the torque density of the rewound five and seven-phase SynRMs is enhanced by 6.56% and 3.37% respectively over the existing machine under rated conditions. The torque ripple is also reduced by 17.13% and 15.87% respectively. Further, the efficiency is enhanced with the rewound machines by 0.3% at rated condition. Moreover, the torque gain is greatly increased to 23.48% at higher speed (9000rpm) and the efficiency is also increased by 3 %. The main advantage of the rewound machine is clearly observed in case of an open circuit fault. With one-phase opened, the rewound machine can work at 78% of the healthy rated torque, while the three-phase machine works at only 43% with a very huge torque ripple about 228%. Experimental measurements are obtained to validate the theoretical work.

In order to describes an investigation of interior permanent magnet (IPM) synchronous machines with higher winding factor, this paper presents a detailed comparisons of the 18-slot/10-pole IPM machine equipped with two coil pitches with conventional one coil pitch fractional slot 18-slot/10-pole machine for applications that require optimal flux-weakening operation, which are including the predicted air gap flux density, back-EMF, average torque, torque ripple and d-axis and q-axis designed by finite element analysis (FEA). With this result, a better structure is carried out to determine the coil pitch, compared with the one coil pitch machine, the two coil pitches increase the winding factor and have better performance in the machine without significant increases in the ripple torque.

Fractional slot concentrated winding (FSCW) permanent magnet synchronous machines (PMSMs) have been a research hotspot over the past few decades. Recently, the magnetic gearing effect in FSCW PMSMs is revealed along with its gear ratio, which is a function of slot/pole number combination. At the design stage of FSCW PMSMs, one of the key issues is the selection of the slot/pole number combination. This paper shows that the gear ratio can contribute to a proper slot/pole number selection in any multiphase FSCW PMSMs by acting as a unified index for a quick overall performance comparison. In this paper, first, the magnetic gearing effect in FSCW PMSMs is explained and the gear ratio is further discussed. The advantages of adopting gear ratio as the overall performance index over other indices are revealed. The influence of the gear ratio on the winding factor, torque output, cogging torque, inductance, and rotor losses of three- and six-phase FSCW PMSMs is analyzed and validated by experiments, thus proving the analyses.

In this paper, the stator-slot/rotor-pole pair combination principle of flux-reversal permanent magnet machines is proposed considering both magnetization modes and magnetic flux leakage effects. First, arbitrary slot/pole combinations with different magnetization modes exhibit compensation effect or are not investigated and the reason why some special slot/pole combinations without compensation effect still exhibit a rather sinusoidal back electromotive force (EMF) is unveiled. Then, the winding factor of back EMF is given and the effect of slot/pole combination on electromagnetic performances is investigated. Finally, specific slot/pole combinations exhibiting fault-tolerant capability are also discussed. Correspondingly, the experiments are constructed to verify the theoretical analysis. Finally, a determination principle for reasonable slot/pole combining is summarized, where both the magnetization mode and coil pitch can be obtained aiming at maximum back EMF. Additionally, the proper slot/pole combinations suitable for different load conditions and fault-tolerant applications are also highlighted.

Permanent magnet vernier (PMV) machines, as one of the flux modulation machines, have gained considerable attention due to inherent high torque density and low torque ripple. This paper mainly investigates the torque performance of PMV machines with different stator tooth topologies. First, it begins with the theoretical analysis of surface-mounted PMV machines, which has a generic number of flux modulation poles (FMPs), PM poles, and armature poles. Then, the expression of flux linkage, back-electromotive force (EMF) and electromagnetic torque are derived successively, where the equivalent winding factor is proposed and defined to evaluate the flux modulation of stator auxiliary teeth and multi-harmonics coupling effect. Next, the back EMF, torque, power factor, flux-weakening capability, and PM demagnetization of PMV machines with different number of stator teeth are analyzed and compared. The final results of theoretical analysis and finite-element analysis can match well. Meanwhile, the non-uniform distribution of FMPs for increasing the average torque is first proposed and analyzed. A parameter K titled as FMP ratio is defined to evaluate the relationship among the angles among FMPs, the influence of the variation of K on the back EMF and torque is deeply explored and analyzed. Besides, the optimal range of K is carefully validated, which will help to optimize the design parameters more conveniently in the future.

In this paper, in order to increase the space for windings and torque capability, a novel yokeless and segmented armature axial field flux-switching sandwiched permanent-magnet (YASA-AFFSSPM) motor which is appropriate for direct-drive applications is proposed. The proposed motor is composed of single stator and two rotors. Stator winding has unit displacement winding factor. Moreover, two rotors are displaced by π (elec.) shift. The unaligned rotors are employed to achieve yokeless and segmented armature structure and also reduce the cogging torque. A three-phase 12/19-pole YASA-AFFSSPM motor is designed. This proposed motor and conventional AFFSSPM are optimized and compared with the conventional AFFSPM. It is shown that the YASA-AFFSSPM motor exhibits higher torque density and greatly lower cogging torque. To evaluate the static and dynamic performance of the YASA-AFFSSPM motor, the sensor-less control drives have been applied. A prototype of the optimized YASA-AFFSSPM motor is manufactured and tested.

A quantitative analysis and design guideline for dual-permanent-magnet Vernier machine (DPMVM) are presented in this paper. First, by winding factor analysis for dominant air-gap harmonics, torque components excited by stator PMs and rotor PMs are quantified, which reveals that, in DPMVM, the rotor PMs essentially have higher torque generation ability than stator PMs, due to the effective utilization of fundamental PM harmonic without flux modulation. Furthermore, mutual influence between dual PM sources is analyzed. It is revealed torque contribution of stator PMs is unilaterally affected by design parameters of rotor PMs. Finally, a design guideline is provided for DPMVM, considering the design priorities of dual-PM sources. Finite element simulation and prototype experiments prove the validity of the theoretical analysis.

In this paper, existing feasible slot/pole combinations of the fractional slot permanent magnet (FSPM) machines are extended. In comparison with the existing slot/pole combinations, the proposed ones could result in a higher winding factor, lower torque ripple, and lower cogging torque. This diversity in the number of the slot/pole combinations brings the designers more alternative solutions. To reach such slot/pole combinations three-slot pitch coils are applied. The existing slot/pole combinations are limited to the designs with an integer number of slots per phase in one periodicity of the FSPM machine. In the presented work, FSPM machines with fractional numbers of the slots per phase in one periodicity of the machines are introduced. However, the phase back electromotive force signals are balanced. Moreover, to achieve a slot/pole combination with small unbalance magnetic force (UMF) and low THD value of the armature MMF, the multilayer winding technique is applied. In addition, a simple technique is presented to find an arrangement of the multilayer winding with very small UMF. Extensive finite element simulations are used to compare the FSPM machines with the proposed slot/pole combinations with the traditional FSPM machines.

This paper proposes a novel shaped-magnet surface permanent magnet machine design concept featuring magnets shaped according to a sinusoid plus a third harmonic along the axial direction, and full-pole-pitched distributed stator windings with a unity winding factor to provide high torque density with essentially zero torque ripple for high-performance motor applications. The magnet thickness is uniform along the radial direction so as not to impair the magnet's ability to handle the demagnetization force. The proposed design was compared against a full-pole-pitched magnet design with maximum magnetic loading and a conventional bread-loaf magnet design. The results demonstrate that the proposed shaped-magnet design uses the magnet materials efficiently to achieve torque density comparable to that of the full-pole-pitched magnet design, and essentially zero torque ripple without compromising its resistivity against a demagnetization force, which conventional bread-loaf magnets cannot offer.

This paper analyzes the operation principle of a short-pitched flux-bidirectional-modulation machine, with especial efforts in terms of its torque component quantification and back EMF harmonics reduction. With the bidirectional-flux-modulation effect, increased equivalent permeance of the air gap is constructed to enhance the machine torque production. Meanwhile, with the shorted-pitched distributed winding design, the electrical gear ratio of machine is increased to realize boosted torque production, and a variety of back-EMF harmonics are eliminated, thus the torque ripple is reduced. In this paper, the machine operation principle is analyzed based on a simple magnetomotive force-permeance analytical model. The torque components and back EMF harmonics are deduced by winding factor analysis. It is revealed that in the proposed machine, the excitation fields with pole pairs of 2, 22 and 46 have generated the effective back-EMF and constant torque and their contribution percentages are 77%, 20% and 3% respectively. Rotor-PM and stator-PM contribute 59% and 41% of the torque respectively. With the 5/6 short-pitch design, the $3^{\mathrm {rd}}$ , $5^{\mathrm {th}}$ and $7^{\mathrm {th}}$ back-EMF harmonics are reduced by 55%, 88% and 88% respectively and the THD of back-EMF is reduced 56.8%. A prototype is fabricated and tested for experimental verification.

In modern aerospace electromechanical actuators (EMA), the integrated structure has brought many advantages, such as reducing system components and system volume, etc. In this paper, the design of dual three-phase winding permanent magnet synchronous machine (PMSM) for an integrated EMA is addressed. The motor adopts slot pole combination of 12/10 because of a high winding factor and utilization. The motor is integrated with the EMA system, so the size of it is strictly restricted. Under the condition of limited size, the most suitable stator split ratio is found by analytical calculation and then verified through finite element simulation. Then through the analysis and comparison of three winding configurations, the double-layer winding phase shift 180 degree is selected. Finally, in the case of considering the eddy current loss on the rotor, the optimal design is carried out to obtain the optimal output torque and reduce the torque ripple.

A six-phase electronic pole changing winding induction machine with 4/2-poles is discussed in this paper. The improved winding factor of the six-phase pole changing winding during high pole number operation over the conventional three-phase windings is discussed. It is also shown that when operating with the lower number of poles, due to the reduction of the spatial angular separation between the three-phase groups, the 3rd harmonic current injection is possible and results in enhanced torque capability and an increased flux weakening region of operation. Finite Element Analysis (FEA) is used to determine the impact of pole changing and the 3rd harmonic injection on torque ripple and also to determine the optimum 3rd harmonic to fundamental current ratio that maximises the peak torque capability. The simulation results demonstrate the behaviour of the six-phase pole changing winding induction machine with the 3rd harmonic injection.

Researches on more electric aircraft (MEA) are actively conducted. It is necessary for realizing MEA to meet aircraft application requirements: high ability, high availability, and high-power density, while aiming to reduce weight and environmental impact. For example, interior permanent magnet synchronous motors (IPMSMs) are expected to be used for aircraft applications of MEA, because IPMSMs can achieve both high-power density and high efficiency at high speed and high torque area compared to other types such as induction motors. In general, IPMSMs with concentrated winding structure are available to utilize limited space effectively. Rectangular windings allow high winding factor and realizing more high-power density motors, whereas eddy current loss in rectangular windings is much higher than that in round windings. In this paper, high-power density concentrated winding IPMSMs that employ rectangular windings are discussed. We have examined three improvements for a reduction of the eddy current loss in the rectangular windings to attain continuous operation with high-power density in this motor. In order to reduce the eddy current loss in the windings situated in front of the rotor, we adopted an asymmetric tooth-tip. Moreover, an adequate groove shape between tooth and stator yoke allows to reduce the eddy current loss in stator yoke side windings. Windings, which have optimized unequal cross-sectional area, offer to reduce whole winding loss. Finally, we present a proposed motor employing the three improvements.

Multi-phase permanent-magnet synchronous machines (PMSMs) have been widely used in safety critical applications due to its fault-tolerant ability. In this paper, the slot opening distribution for fraction slot winding and its influences on the winding factor and the coil pitch are analyzed, based on which several six phase fault-tolerant PMSMs with different slot opening distributions are proposed. The performance, including the magnetomotive force (MMF) harmonic spectrum, the eddy loss and the cogging torque, is evaluated in healthy condition. For the open-circuit and short-circuit condition, the performance before and after the fault-tolerant strategy adopted is compared and analyzed in terms of the MMF spectrum and the inductance feature. The tradeoff design of the slot opening distribution considering the fault-tolerant ability and the performance in healthy condition is concluded, which provides a generally guideline on the design of fault-tolerant PMSM.

6-slot/2-pole permanent magnet (PM) motors with tooth-coil windings are employed widely for high-speed application due to short end-winding and no inherent magnetic force. However, tooth-coil windings can be replaced by 2 and 3 coil-pitch windings for winding factor improvement. Different winding configurations mainly affect winding factor and end-winding length, and consequently average torque and torque density. In this paper, three 6-slot/2-pole high-speed PM (HSPM) motors with 1, 2, and 3 coil-pitch windings are optimized for maximum average torque by finite element method (FEM). Their electromagnetic performances are then compared, accounting for the influence of motor axial length and end-winding. It is found that for high-speed application, compared with 1 and 3 coil-pitches, 2 coil-pitch has a good trade-off between winding factor and end-winding axial length which are attractive for high efficiency and large torque density.

This paper researches the possibility of changing the stator of existing three phase synchronous reluctance motors to achieve improved multiphase machines performance, keeping the same rotor. An optimal design for the stator is proposed. Thus, several geometrical constraints are imposed such as fixed inner stator bore diameter, air gap length and axial stack length. Analysis and discussion to select the optimal dimensions of the proposed multiphase stator with no extra cost in both iron and copper are provided, considering a main goal to achieve a higher torque gain and a minimum torque ripple. By means of finite element magnetic simulation, two stator designs (60 and 40 slots) are simulated and compared with the 3-phase (36 slots) SynRM. It has been found that a 5-phase SynRM with 60 slots stator gives better performance compared to a 3-phase SynRM: the average torque is increased by 11.78%, the efficiency and the power factor are increased by around 0.72% and 5.54% respectively compared to 3-phase. However, the torque ripple becomes slightly higher, but within the permitted range (

Five-phase machines were suggested as an optimum in literature to improve the torque density of electrical machines. This target can be reached by a suitable third harmonic phase current injection which leads to a better utilization of the active machine parts especially the lamination material. Hence, a fivephase IPMSM was designed, built and validated to prove the torque influence by using the third harmonic. After a basic system description this paper shows a reasonable machine design with concentrated windings to use additionally to the fundamental also the third harmonic for torque production. Following, this paper is completed by presenting the used validation process and the comparison of simulation and measurement results.

Under the adverse trend of fossil energy attenuation and air pollution, wind power effectively alleviates the global energy crisis and environmental pollution. For wind turbines, especially large offshore wind turbines, their transportation, installation, and maintenance are very inconvenient. In order to solve this problem, this paper presents an E-core stator modular machine which inserts stator gap into the unwounded teeth of the fractional-slot concentrated winding (FSCW) permanent magnet (PM) machine. The winding factor of the new stator structure machine was derived. The electromagnetic models of 12-slot/10-pole and 12-slot/14-pole modular FSCW PM machines and traditional FSCW PM machines were established using the finite element analysis (FEA) software, and the open-circuit flux density, cogging torque, load torque, loss, and efficiency were simulated and analyzed. The results showed that the modular structure of E-core stator not only simplified the transportation, installation, and maintenance of wind turbines, but also optimized the electromagnetic performance of the 12-slot/14-pole machine, i.e., improved the output torque and operation efficiency.

This paper investigates the influence of stator slots and rotor pole pairs combinations on torque performances in rotor permanent magnet flux switching (RPM-FS) machines. Based on a magnetomotive force (MMF) permeance model, the candidates of stator slots and rotor pole pairs combinations with higher torque capability can be determined by analyzing the PM-MMF and winding factor. Meanwhile, the candidates with a lower torque ripple can be obtained by referring to the cogging torque, which is related to the greatest common divisor of stator slots and rotor pole pairs. In addition, from the field modulation principle, the RPM-FS machines with the same fundamental magnetic loadings and winding factors exhibit identical fundamental harmonic torque, but different modulation harmonic components. Finally, four candidates with attractive torque performance are chosen, and the characteristics are verified by finite-element analysis and experiments.

International audience; If multi-phase machines equipped with tooth concentrated winding with half a slot per pole and per phaseoffer interesting characteristics (simplified manufacturing, no space subharmonic, fault-tolerant ability), their low fundamentalwinding factors make their designs and controls challenging. The paper addresses the case of a seven-phase Surface-mountedPermanent Magnet (SPM) machine which has a fundamental winding factor lower than the third. This so-called bi-harmonicspecificity is considered in order to achieve good torque quality (average value and ripples). Regarding the design, the magnetlayer is segmented into two identical radially magnetized tiles that cover about three-quarters the pole arc. Regarding the control,the rated Maximum Torque Per Ampere (MTPA) supply strategy (h1h3 control) aims at generating a third harmonic currentcomponent greater than the fundamental. A prototype has been manufactured: the ability of the machine to provide smoothtorque is experimentally confirmed through the implementation of a simple MTPA control which copes with high distortion inno-load voltage.

Axial flux permanent magnet (AFPM) motors are suitable options for solar-powered vehicles due to their compact structure and high torque density. Furthermore, certain types of AFPM machines may be configured without stator cores, which eliminates associated losses and cogging torque and simplifies the manufacturing and assembly. This paper examines two machine designs for use in the solar-powered vehicle of the challenger class—a single rotor, single stator conventional AFPM machine, and a coreless AFPM machine with multiple stator and rotor disks. The response surface methodology (RSM) is utilized for the systematic comparison of the conventional and coreless topologies and to select the optimum designs among several hundreds of candidates. Designs with minimum losses and mass producing required torque with larger air-gap are favored. The performance of the selected designs has been studied via three-dimensional finite element analysis (FEA). The FEA parametric modeling methodology is validated by measurements on three AFPM machines of the conventional and coreless type.

The main purposes of this paper consist of two parts: Firstly, the geometric topology of novel modular spoke-type permanent-magnet (MSTPM) machines with different magnetization modes are introduced. Secondly, based on magnetic field modulation (MFM) analysis and finite element method (FEM), the influence of magnetization on MSTPM machines are investigated with respect to field harmonic, combination of slots and poles, winding factor, back electromotive force (EMF), inductance, eletromagnetic torque, and so on. A prototype machine is manufactured to verify the MFM and FEM predicted results.

This paper investigates the performance of synchronous reluctance motors when the stator is equipped with a combined star–delta winding layout. The conventional star winding is used as a benchmark in this study to compare different possible single-layer winding layouts. Among these different winding layouts, those which maximize the fundamental magneto-motive force component are selected. A simple mathematical formula is then derived to calculate the equivalent winding factor for different shares between star and delta subwindings. It has been proved that for the same copper volume and line current magnitude, the star–delta connection can offer an enhancement in the torque density of approximately 5.2% over the conventional star case under rated conditions. However, this gain is affected by the employed number of poles and stator slots. On the other hand, the effect of the winding layout on either power factor or core loss can be merely neglected over a wide range of speeds and currents. Nevertheless, the machine efficiency under a combined star–delta connection is relatively improved under light loading as a result to the machine torque/current ratio enhancement. The theoretical findings are experimentally validated using two identical 5.5 kW prototype machines, having star and combined star–delta winding connections.

PurposeThe purpose of this paper is to propose a novel axial field flux-switching machine with sandwiched permanent magnets. It is one of the most efficient machines which is appropriate for high-torque and low-speed direct-drive applications. The proposed model is equipped with an advanced phase-group concentrated-coil winding to obtain a unity displacement winding factor. Two configurations of the proposed motors with 6-stator-slot (S)/10-rotor-pole (P) and 12S/19P are investigated. These two structures are compared with optimized a conventional axial-field flux-switching permanent-magnet (CAFFSPM) machine. Unity displacement winding factor increases the back-EMF and electromagnetic torque. Moreover, the prototype 12S/19P motor is built to verify the design. Design/methodology/approachThe torque equation is obtained and the dimensions of the two proposed motors are determined. Some specific design issues, including the stator/rotor pole sandwiching pole angle, the stator tooth angle and the rotor pole angle have been optimized to minimize the cogging torque while maintaining the high torque density by means of response surface methodology (RSM) and 3-D finite element model of the machine. FindingsTo improve the performance, especially at high torque density, low cogging torque and high level of fault-tolerant capability, the 12S/19P axial field flux-switching sandwiched permanent-magnet (AFFSSPM) motor is proposed. Based on the optimized design, a prototype of the 12S/19P AFFSSPM motor is fabricated and tested. It is found that the experimental results validate the 3-D finite element method (FEM) simulation results. Originality/valueThe AFFSSPM motor is one of the most efficient motors, but the 12S/19P AFFSSPM motor with sandwiched permanent magnet and unity displacement winding factor has not been specially reported to date. Thus, in this paper, the authors report on optimal design of a novel axial flux-switching sandwiched permanent-magnet machine for electric vehicles and fabricate a prototype of the 12S/19P AFFSSPM motor.

In this study, the influence of stator/rotor-pole combinations on electromagnetic performance in partitioned stator doubly salient permanent magnet (PS-DSPM) machines is investigated, in terms of open-circuit flux-linkage, back-electromotive force (EMF), cogging torque and on-load torque characteristics. Analytical deduction shows that by modifying the all poles wound winding to alternate poles wound winding in the 12/11- and 12/13 stator/rotor-pole PS-DSPM machines, the fundamental distribution factor and hence the fundamental winding factor can be enhanced, resulting higher torque density. Consequently, among the 12-stator-pole all and alternate poles wound PS-DSPM machines, the 10- and 11-rotor-pole machines exhibit the highest torque density, respectively. However, the 12/10- and 12/14-pole alternate poles wound PS-DSPM machines suffer from higher phase back-EMF even harmonics, resulting larger torque ripple. The 12/10- and 12/11-pole all and alternate poles wound prototypes are built and tested to verify the finite-element analysis.

This paper proposes a novel detached winding configuration for asymmetric six-phase double-stator axial flux permanent magnet machines aiming at fault-tolerant applications. Due to the machine unique double-stator structure, the six-phase winding can be separated into two three-phase windings with 30 electrical degree angle shift and arranged in different stators, which is the basic idea of the detached winding. In this paper, the connection of detached six-phase winding is first given, followed by a comprehensive comparison of the conventional six-phase winding and the detached winding in aspect such as the winding factor, electromotive force, inductances, rotor eddy current loss, and torque in normal condition. Performance under fault-tolerant operation is investigated by the copper loss minimization control strategy. The results show that by applying the detached winding instead of the conventional winding, rotor eddy current losses could be reduced by 25% and 70% under normal and fault-tolerant operation, respectively, without sacrificing torque output. This implies that under fault operation, the excess heating in rotor could be reduced and the machine durability can be enhanced. A prototype machine is built to validate the performance of the detached winding design. The experimental results match well with simulation analysis.

International audience; Multiphase induction machines have the advantage of producing torque under different current harmonics. Theoretically, with some simplifications, the maximum produced torque can be considered proportional to the harmonic winding factor related to the injected current harmonic. However previous work has shown that this theoretical proportionality between the maximum developed torque and harmonic winding factors is not obtained in the case of a five-phase induction machine with eight-poles andfractional-slot tooth concentrated winding. This paper aims to investigate the effect of winding parameters, especially phasenumber, fundamental polarity and stator slots number, on the torque production in multiphase induction machine under harmonics injection. A comparative study is done between four five-phase winding configurations, with the same geometry and copper volume, under both first and third harmonic injection. Finally, a special 15-phase winding presenting better consistency between maximum developed torque and harmonic winding factors is proposed.