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Due to the high-power density and compact structure, axial-flux permanent magnet (AFPM) machines have gradually received much attention with a view to researching breakthroughs in the next generation electric drive technology for electric vehicles in the recent decades. The AFPM machines with factional slot concentrated winding (FSCW) and yokeless stator, namely yokeless, and segmented armature (YASA) motors, have drawn much attention for its high-power density and potential manufacturability due to the concentrated winding and modular stator core configuration. However, the significant rotor loss resulting from the abundant armature reaction harmonics in FSCW machines imposes a great challenge to the rotor heat dissipation, especially when the pursuit of higher speed has become the trend for electric vehicle applications. On the other hand, distributed winding is widely used in high speed radial flux permanent magnet (PM) machines due to its low armature reaction harmonics. In order to figure out the advantages and disadvantages of various winding arrangement and rotor configuration of AFPM for electric vehicle applications, the comparative study of four AFPM machines with various winding configurations and rotor PM arrangements are comprehensively conducted in this article. First, the design and primary optimization of the four AFPM machines are conducted for the electric vehicle requirement specifications. Then, a comprehensive three-dimensional finite-element analysis (FEA) is employed to compare the electromagnetic performance including torque/power density, efficiency, and flux-weakening capacity. Furthermore, the guideline of winding selection of AFPM machines for electrical vehicle is given. Finally, a yokeless stator AFPM prototype with ISDW configuration is manufactured and tested to verify the validity of the FEA results, as well as confirm the comparison conclusion. [ABSTRACT FROM AUTHOR]

Spoke-array brushless dual-electrical-port dual-mechanical-port (SA-DEP-DMP) machine is a good candidate for continuously variable transmission device, because of its high compactness, contactless torque transmission, and decoupled rotors. Due to the specific features, including two independent controllable rotors, two set windings, and complex magnetic field coupling, some unique design considerations of SA-DEP-DMP machine are analyzed in this article. First, there is a little accurate analytical model for DEP-DMP machine. An applicable analytical model is proposed to directly describe the characteristic of air-gap magnetic field and calculate the sizing equation. The key innovation is that the inner air-gap permeance with the slot effect is mapped into the magnetic potential by air-gap mapping model, which simplifies the double air-gap structure into a single air-gap structure. Second, the torques of two rotors are always optimized separately at the same time. Using this design method, the optimal torques of two rotors cannot achieve simultaneously for many parameters. In order to solve this problem, a novel constant torque ratio design method is proposed where two windings electric loading distributions are considered. The influences of key parameters, such as combination of slot and pole, stator split ratio, permanent magnet size, etc., on the torque performances are analyzed based on finite-element analysis. Finally, an SA-DEP-DMP prototype is manufactured. [ABSTRACT FROM AUTHOR]

In very low power drives, a single-phase induction motor is used. This motor, like the 3-phase induction squirrel-cage motor, requires a voltage supply with suitable parameters - of suitable quality, in practice. In energy systems, voltage quality distortions may occur in connection with the deviation of the RMS voltage and the occurrence of harmonics, subharmonics and interharmonics in its waveforms. Subharmonics and interharmonics in the voltage waveforms are particularly detrimental to induction motors. They cause, for example, additional power losses, electromagnetic torque pulsation and motor vibrations. It should be stressed that the existing publications on the impact of the considered distortions on the induction squirrel-cage motor are almost only applicable to 3-phase machines. The article presents the results of research on the influence of subharmonic and interharmonic voltage components on the single-phase induction squirrel-cage motor. [ABSTRACT FROM AUTHOR]

Today, many applications requiring mass manufacturing are shifting to robotic applications through automation systems. The actuators used in these robotic systems should be designed according to needs. In this study, an air core spherical motor which has rotor and stator winding arrangement is described. The spherical motor's windings are optimally positioned on the stator made of delrin. Mutual inductance and self-inductance change were examined according to r=4, 20, 40 and 60 mm radius and the change in the number of stator winding for the spherical motor. Changes in inductance were found through curve fitting method with the coefficients of cubic equations. Equivalent circuit with winding inductance model is also given. Torque change according to magnet change was also investigated. Magnetic flux density change of N52 M magnet 3 winding 2-pole model was examined and the effect of the increase in overall size on torque was evaluated. [ABSTRACT FROM AUTHOR]

The TC48 drive is a low-cost, low-voltage integrated motor-drive solution suitable for mild hybrid electric vehicles, off-highway traction, and any application where a compact, highly torque-dense machine is required. Low-voltage solutions for electric vehicles are attractive to manufacturers due to lower insulation requirements, and hence lower cost. The package is based on a six-phase switched reluctance machine, which uses a novel stator topology and unique winding design to achieve high torque density. The power electronics converter hardware is integrated into the motor housing, giving a physically, electrically, and thermally optimised solution. The complete package has been designed to be suitable for manufacturing in high volumes. This study describes the electromagnetic design of the motor, the mechanical innovations used to physically realise this design, and the cooling system which makes the high power density possible. The integration of the power electronics and their control is also discussed. The project is the result of collaboration between Newcastle and Loughbosrough Universities, RDM Ltd., Productiv, Infineon, Tata Steel, and Libralato. [ABSTRACT FROM AUTHOR]

A series of systematic studies are carried out to investigate the influence on torque density and power density on machine speed rating. Several series of permanent magnet machine designs are established using an array of different electrical and thermal design constraints. The paper demonstrates that torque density in permanent magnet machines tends to decrease with speed rating due to complex interplay between electromagnetic and mechanical considerations, e.g. fixed winding current density, fixed split ratio etc. Interesting trends are observed, including cases in which there is an optimum rotational speed in terms of power density, beyond which the power density starts to decrease with increased speed rating. [ABSTRACT FROM AUTHOR]

This study presents a comparative study of different modular brushless wound rotor synchronous machines (MB-WRSM) using non-overlapping fractional slot double-layer concentrated windings. The goal of the study is to highlight the structure which offers the best fault-tolerance capability and the highest output performance. The fundamental winding factor is calculated by using the method based on voltage phasors as a significant criterion to select the preferred numbers of phases, stator slots, and poles. With the limited number of poles for a small machine (3.67 kW/7000 rpm), 15 different machines for different phase/slot/pole combinations are analysed using two- dimensional (2D) finite element method and compared according to three criteria: torque density, torque ripple, and machine efficiency. The seven-phase/seven-slot/six-pole machine is chosen with the best compromise of high torque density, small torque ripple (3.89%), and high nominal efficiency (95%). This machine is then compared with a reference design surface-mounted permanent magnet synchronous machine (SM-PMSM). The simulation results are discussed and demonstrate that the MB-WRSM presents interesting performance features, such as extended field weakening range, with overall performance closely matching that of an equivalent SM-PMSM. [ABSTRACT FROM AUTHOR]

Here, the selection of optimal slot/pole (Ns-slot/pr-pole) number combination between the pairs of fractional slot concentrated winding (FSCW) permanent magnet synchronous machines (PMSMs) with Ns = 2pr ± 1 or Ns = 2pr ± 2 will be analysed by a modified winding function accounting for slot opening and validated by finite element method. The results show that for FSCW PMSMs with Ns = 2pr ± 1 or Ns = 2pr ± 2, the higher pole machine will have larger winding factor and hence better torque performance than the lower pole one. Moreover, it also reveals that this torque advantage is more evident in the external rotor machine than that in internal rotor machine. [ABSTRACT FROM AUTHOR]

A dual three-phase machine with interior permanent magnet rotor and distributed winding has been studied and compared to a commercial automotive traction machine, the Nissan Leaf IPM machine. The performance of the two designs are compared for typical traction operating points, via high torque, low speed and low torque, high speed, and constant power field weakening operation. The dual three-phase machine is shown to have improved torque density and torque quality without compromising efficiency. [ABSTRACT FROM AUTHOR]

In this study, a novel partitioned stator hybrid excited machine is proposed, in which the excitation sources including both permanent magnets (PMs) and field windings are allocated on the secondary stator that is separated from the original stator having armature windings. As a result, the available space is boosted to improve the torque density and flux regulation capability. Meanwhile, the rotor is simple without coil or PM. The PMs on the stator is placed on the slot openings between the two neighbour tooth tips, with which the uncontrolled voltage of the proposed machine is limited and it is favoured for safety-critical applications. The machine topology and operating principle are introduced in detail, and the basic electromagnetic performance is evaluated based on finite element method to validate the analysis. [ABSTRACT FROM AUTHOR]

In this study, the performance of a triple redundant nine-phase permanent magnet-assisted synchronous reluctance motor with delta-connected windings is comprehensively assessed and compared with that of wye-connected winding under healthy and fault conditions, including open circuit, inter-turn short-circuit and terminal short circuit. The steady-state torque behaviour, loss, efficiency and temperature distribution of the two winding configurations are analysed and compared. It is shown that the delta-connected winding has higher output torque under one phase open-circuit fault and lower inter-turn short-circuit current with three-phase terminal short circuit. [ABSTRACT FROM AUTHOR]

This study investigates the field-weakening capability of interior permanent magnet (IPM) and surface-mounted permanent magnet (SPM) machines with distributed windings by considering phase voltage distortion in field-weakening region. For analysis and comparison, the Nissan Leaf vehicle traction machine is studied as a reference benchmark machine and then a comparable SPM machine is designed within the main constraints of the benchmark machine. A finite element analysis model of the benchmark machine is developed and validated by published experimental measurement. Sinusoidal phase current is desired to enhance machine torque performance and power electronic converters employing vector control method are commonly used for traction machine supply. However, the machine terminal phase voltage distortion may introduce additional difficulties for machine control. Therefore, firstly, phase voltage distortions of IPM and SPM machines with distributed windings are compared and the mechanisms are discussed. Due to the voltage distortion, the peak value of phase voltage may be higher than the fundamental one. Therefore, the influences of IPM and SPM topologies on machine traction characteristics are investigated. The study indicates that SPM machines with distributed windings can be designed to achieve comparable torque and power performance and better field-weakening capability compared to IPM machines. [ABSTRACT FROM AUTHOR]

This paper proposes a novel winding layout for the electric machines with fractional-slot concentrated windings (FSCW) using a stator shifting concept, with which all the non-working harmonics can be completely cancelled or significantly reduced and the non-overlapping winding can be kept. First, the basic winding layout with a 24-slot 14-pole machine to reduce the significant 1st sub-harmonic will be presented for machines with single-layer (SL) windings. From this, a novel double layer (DL) winding layout using the stator-shifting concept will be introduced. By adopting two SL winding sets with a 105° mechanical angle shift with respect to each other, it is not necessary to use overlapping windings. With this configuration, the 1st sub-harmonic will be completely cancelled and the parasitic 5th harmonic will be significantly reduced. Hence, the rotor losses, specifically magnet loss will be significantly reduced. Finally, two PM machines with different DL winding layout, namely, conventional 12-slot 14-pole and 24-slot 14-pole machine, will be designed and compared to validate the advantages of this winding topology. [ABSTRACT FROM AUTHOR]

Here, the authors present a magnetic circuit design with a multilayer air gap winding. This design provides a new degree of freedom in the design process. The approach is based on a single layer air gap winding, which demonstrates the ability to scale, permitting application in small and large electric machines. A meandering structure with coils arranged parallel to the rotation axis are mounted in several layers on a slotless magnetic core. The authors consider a fixed ohmic power loss boundary condition to compare this approach with an existing validated machine design. Machine current is reduced with each winding layer, while self-inductance and induced voltage are increased. Since the air gap height is increased with every additional layer, the useable magnetic flux density decreases. Accordingly, an utilisable range in which optimal torque output is obtained can be described analytically. The authors provide comparison between a single-layer winding design, which achieves the global optimum torque, and a four-layer winding design, which gives a 16-fold increase in the phase self-inductance. Additional thermal simulations prove that the multilayer design give the same ohmic power losses as the single layer design, without having any thermal issues and hot spots. [ABSTRACT FROM AUTHOR]

The Electric Solar Wind Sail is an innovative propulsion system that gains thrust from the interaction of the incoming ions from the solar wind with an artificial electric field produced by means of long charged tethers, which are deployed and maintained stretched by rotating the spacecraft around a spin axis. Under the combined interaction between solar wind dynamic pressure and centrifugal force, the tethers reach an equilibrium configuration whose spatial shape must be known for obtaining a reasonable estimate of the propulsive acceleration, a fundamental information for preliminary mission analysis purposes. This problem has been addressed in recent papers, which deal with the analytical expressions of thrust and torque vectors of a spinning and axially-symmetric Electric Solar Wind Sail. The torque acting on the sail induces a perturbation on the orientation of the thrust vector, which is here studied by analyzing the attitude dynamics. Numerical simulations show that the spacecraft motion is characterized by an undamped precession combined with a nutation motion. The effect due to the torque acting on the spacecraft is to align the thrust direction along the Sun-sail line, thus reducing the maneuvering capabilities. This paper proposes an effective control law which is able to remove the torque by suitably adjusting the tether electric voltage. It is shown that the proposed solution maintains the nominal thrust magnitude, and requires a small electric voltage modulation. • This paper investigates the effects of the E-sail inflection on its attitude dynamics. • An analytical model is presented to describe the E-sail torque vector. • The attitude dynamics are simulated with small sail pitch angles. • The E-sail shows to perform a combined precession-nutation motion. • The paper presents a strategy to remove the torque by modulating the tether electric voltage. [ABSTRACT FROM AUTHOR]

This paper investigates the torque production and the torque ripple reduction of a six-stator/seven-rotor-pole (6/7) variable flux reluctance machine (VFRM). As a main advantage, the 6/7 VFRM produces higher torque density, but less torque ripple compared with the 6/4 VFRM. The instantaneous torque equation of the 6/7 VFRM is derived by considering the spectra of the winding inductance and current. Based on the derived equation, the average torque is found to be mainly produced by the mutual inductance between the field and armature windings. The even-order harmonics of self-inductance and odd-order harmonics in mutual inductance between the field and armature windings are eliminated due to the opposite polarity connection of the armature coils in each phase. This results in the elimination of the third harmonic torque ripple, while a multiple of the sixth harmonic torque ripple exists. In order to mitigate the sixth harmonic torque ripple, the harmonic current injection method is implemented into the field winding. The field harmonic current is calculated from the analytical torque ripple equation. The performance of the proposed methods is verified by both finite element analysis (FEA) and experiment. [ABSTRACT FROM AUTHOR]

In this paper, the open-circuit dc-winding-induced voltage in a wound field switched flux (WFSFs) machines is analyzed. The phenomenon of open-circuit dc-winding-induced voltage is illustrated and the mechanism is explained. Rotor skewing is proposed to reduce the open-circuit dc-winding-induced voltage, and the optimal skewing angle is analytically derived based on the analytically deduced harmonic orders of the open-circuit dc-winding-induced voltage. Finite-element (FE) analyses show that the open-circuit dc-winding-induced voltages in the analyzed 12-stator-pole partitioned stator WFSF machines having 10-, 11-, 13-, and 14-rotor-pole rotors can be effectively reduced by >94%, while the ac-winding phase-fundamental back-EMFs can be maintained by >95%. Twelve/ten-stator/rotor-pole prototypes with skewed and nonskewed rotors are built and tested to verify the analytical and FE results. [ABSTRACT FROM AUTHOR]

This paper presents a novel consequent-pole permanent magnet (CPM) machine featuring N-S-iron–S-N-iron sequences to eliminate the even-order harmonics of phase back electromotive force (EMF) and the unipolar leakage flux in the end region. The flux barrier is employed to improve the symmetry of the air-gap flux and reduce the saturation of the stator yoke, and hence the output torque can be improved. The proposed CPM machine, as well as its conventional counterpart with N-iron sequences, is optimized by finite-element analyses. Moreover, the electromagnetic performance of the proposed CPM machine, including the open-circuit air-gap flux density, back EMF, average torque, torque ripple, loss, efficiency, and unipolar leakage flux, is compared with the conventional CPM and surface-mounted PM (SPM) machines. Although both the proposed and conventional CPM machines have lower output torque than the SPM machine, the utilization ratio of PM material is increased by >33%. It is demonstrated that the proposed CPM machine has similar output torque and efficiency, but much lower torque ripple compared to the conventional one. Moreover, unipolar leakage flux does not exist in the end shaft of the proposed machine, and thus, the magnetization of the mechanical components can be effectively eliminated. Finally, the 9-slot/6-pole CPM machine is prototyped and measured to validate the analyses. [ABSTRACT FROM AUTHOR]

The dual-winding fault-tolerant permanent magnet motor (FTPMM) incorporates the merits of high power density and high efficiency of the permanent magnet (PM) motor and high fault-tolerance of the single FTPMM. In this paper, a three-phase dual-winding FTPMM is investigated to study fault-tolerant control strategy. To generate the same output torque and reduce the torque ripples under healthy, winding open-circuit fault and winding short-circuit fault conditions, the current vector fault-tolerant control strategy is proposed. The currents under one-phase open-circuit and short-circuit failure conditions are calculated in detail. The torque ripples and copper loss are obtained and compared with other different fault-tolerant strategies. The simulation model of the dual-winding FTPMM drive is built and the hardware experimental platform based on TMS320LF28335DSP is developed. The simulation and experimental results have proved that the proposed dual-winding FTPMM has good operation performance under healthy condition, and the proposed vector fault-tolerant control strategy can compensate the function of faulty phase to obtain the invariable torque with small ripples under open-circuit and short-circuit fault conditions, which verified the proposed current vector fault-tolerant control strategy correct and valid. [ABSTRACT FROM AUTHOR]

In this paper, a design method for a wound field synchronous motor (WFSM) employing the dual stator winding and the winding connection change circuit is proposed. Through the design method, the WFSM can be operated as two different modes, and each mode is determined by the connection between the stator windings U, V, W and X, Y, Z. By applying the proposed method to the conventional WFSM, the operation mode of the motor is changed at a certain speed. The speed for the mode change is determined to maximize the efficiency of the machine. As a result, through the mode change, the line to line induced voltage, current phase angle, and phase resistance are decreased. In addition, the demand field current is also reduced to achieve the required torque due to the salient pole characteristics of WFSM. Consequently, the efficiency of the WFSM is increased due to the mode change. Finally, the effect of the proposed method and the validity of the simulation results are verified by the load test. [ABSTRACT FROM AUTHOR]

DC winding induced voltage pulsation in the wound field synchronous machines (WFSMs) will cause dc winding current ripple, challenge the dc power supply, and deteriorate the control performance, especially at high speed. In this paper, the influence of dc winding configuration including the dc coil number and the parallel branch number on its induced voltage pulsation is investigated for WFSMs. Based on the modeling of both open-circuit and on-load dc winding induced voltages, the preferred dc winding configurations for WFSMs having various stator/rotor pole number combinations with double layer or single layer ac windings are obtained and validated by finite element (FE) analysis on four typical partitioned stator WFSMs (PS-WFSMs). A PS-WFSM prototype is built and tested to validate both analytical and FE analyses. [ABSTRACT FROM AUTHOR]

This paper presents the design and analysis of fractional-slot concentrated-windings for use with direct liquid cooling. To achieve considerably higher torque density than state of the art of electrical machines, recently patented cast coils that allow slot fill factors up to 90% are considered as basis for further enhancement. The sensitivity of large conductors to high losses due to current displacement as well as the implementation of direct liquid cooling of every single conductor is discussed. Two innovative coil designs are developed and compared, in consideration of current displacement using finite element methods, with basic trapezoidal cast coils. The heat dissipation capacities of the new coil designs are tested analytically as well as by measurement. Additionally, different cooling mediums are compared for their suitability for direct liquid cooling of coils. The proposed coil designs lead to possible current densities of 100Amm2 and to a reduction of the additional losses to about 50%. [ABSTRACT FROM AUTHOR]

Comparison of the electromagnetic performance of a flux-switching permanent magnet (PM) machine having two separate stators as well as different winding topologies is investigated in this paper. Different stator and rotor pole combinations of these machines are also considered. The analysis includes the open-circuit and on-load characteristics of the analyzed machines. It is observed that, the largest fundamental values of electromagnetic torque, for each winding topology, is seen in the 11-rotor-pole and 10-rotor-pole machines having alternate- and all-pole-wound configurations, respectively. Moreover, significant ripple is observed in the waveforms of the even-number rotor pole machines compared to their corresponding odd-number rotor pole counterparts. Overall, the alternate-pole-wound machines essentially have larger torque-density than their equivalent all-pole-wound ones. The investigated machine is also tested for validation. [ABSTRACT FROM AUTHOR]

In this paper, the optimal design for a permanent magnet-assisted synchronous reluctance motor (PMA-SynRM) is proposed in terms of efficiency, maximum torque, and minimum torque pulsations. Design variables, objective functions, and constraints are selected for this optimal design, which is divided into two steps. Step I utilizes the pole/slot combination of the PMA-SynRM and winding methods. The chosen 4-pole/36-slot model with distributed winding maximizes the rated efficiency. In Step II, the optimal design of the stator parameters is obtained using the response surface method and the precise torque and torque ripple are calculated using the finite-element analysis (FEA). The proposed stator slot openings are minimized to minimize the air-gap flux leakage, and consequently, realize a smooth electromagnetic torque. Finally, a few FEA results are validated by experimental results. [ABSTRACT FROM AUTHOR]

In this paper, improvement of torque quality and magnetic losses of a concentrated winding high-speed permanent magnet (PM)-assisted synchronous reluctance motor (PMaSRM) that can operate in the wide speed range are investigated. Optimization studies have been carried out to enhance the torque quality. In addition, ac copper losses in the stator coils and iron losses in laminations at high frequencies have been investigated. Since the PMaSRM can operate in a wide constant power-speed range, the field weakening performance has also been investigated. The motor performance results of the PMaSRM at both no-load and on-load conditions are examined by using Flux 2-D FEA software. A prototype motor based on the simulations has been built and validated in order to show the feasibility of such technology for white good applications. [ABSTRACT FROM AUTHOR]

In this paper, an integrated motor-drive and battery-charging (IMB) system with a doubly salient electromagnetic machine (DSEM) is proposed to be implemented for electric vehicles. In the driving mode, the front-end dc/dc converter is employed to boost the battery voltage to improve the speed range and acceleration ability of the DSEM. The field windings distribution of a 12/10-pole DSEM is arranged for the constant self-inductance, and adopted as the inductance of the front-end dc/dc converter to eliminate the traditional filter inductance and excitation loss of the machine. In the charging mode, the windings of DSEM could be exploited as the filter inductances to obtain the unity power factor operation and constant current charging ability. The simulations and experiments have been accomplished to verify the feasibility of the independent field current control method for the proposed IMB system. [ABSTRACT FROM AUTHOR]

This paper presents an investigative study on a dual-stator spoke-type vernier machine (DSSTVM) suitable for direct-drive electric vehicle (EV) propulsion systems. DSSTVM was a superior choice as a direct-drive motor because of its high torque density per volume, wide speed range operation, and high power factor, which are critical features for the direct-drive EV propulsion system. However, previous research on DSSTVMs was restricted to conventional 12 slots and 20 poles (12S20P) with distributed windings. Thus, the 12S22P combination, which has a higher gear ratio, was presented to enhance the torque performance. Different winding configurations were also considered to further improve the performance, as concentrated and distributed windings in vernier machines show different performances due to their different vernier effects and different end windings. A total of four models, 12S20P and 12S22P models with concentrated and distributed windings, were suggested and compared. The finite-element method analysis was performed to confirm the characteristics of each model. Consequently, the 12S22P model with a distributed winding was chosen for EV applications due to its good overall performance. [ABSTRACT FROM AUTHOR]

This paper proposes a novel multi-phase double-winding vernier permanent magnet (DW-VPM) wind power generator applied for hybrid ac/dc microgrid. The key is to employ two sets of windings, namely, ac windings and dc windings in the machine, which serve to produce ac power and dc power for microgrid, respectively. The permanent magnets (PMs) are surface mounted on the rotor, and the stator is designed with open slots. The stator teeth can act as flux modulator for the permeance difference between the stator teeth and the air. Therefore, the field excited by PMs can be effectively modulated. Besides the original harmonic used to induce sinusoidal back electromotive force (EMF) in the ac windings and generate ac power, another low-order harmonic can be generated, which is used to induce square wave EMF in the dc windings and generate dc power through diode-bridge rectifier. Since multi-phase windings can get the square wave EMF more easier, the dc windings are designed with six phases. By using time-stepping finite-element method, the electromagnetic performances of the proposed DW-VPM wind generator are comprehensively investigated and verified. [ABSTRACT FROM AUTHOR]

This paper proposes a novel dual-sided permanent magnet memory machine (DSPM-MM) by combing the distinct advantages of “high torque density” of conventional rotor-PM machine and “convenient online PM flux control” of stator-PM MM. In the proposed design, the consequent-pole NdFeB PMs are placed in the rotor, whereas the low coercive force (LCF) PMs are mounted between the adjacent stator teeth to enable flexible air-gap flux adjustment. Meanwhile, since the LCF PMs can be either remagnetized or demagnetized bidirectionally by a current pulse, the associated flux-weakening copper loss is eliminated, and hence, the proposed DSPM-MM can maintain high efficiency operation over a wide operating range. The machine topology and operating principle are introduced and addressed from the perspective of the nonlinear hysteresis behavior of LCF PMs as well as dual flux modulation effect, respectively. Then, the electromagnetic characteristics of the proposed machines having various available rotor poles are investigated and compared. The feasibility of the proposed design is validated by both finite element and experimental results. [ABSTRACT FROM AUTHOR]

This paper addresses the design and investigation of an improved torque density dc-biased Vernier reluctance machine (dc-biased-VRM), which is characterized by salient rotor structure, and merely one set of concentrated windings in stator. First, a 12-stator slot, 10-rotor slot dc-biased-VRM is designed. Then by analyzing the magnetic flux distribution with finite-element analysis, it is found that the flux always doesn’t flow across half of the stator teeth. Therefore, these teeth are removed and a novel 6/10 dc-biased-VRM with 20% higher torque density is obtained. Besides, by optimizing the stator/rotor tooth width combination and tooth shape, the torque ripple is lowered. Finally, a prototype is manufactured and experimental results show good agreement that is observed between the simulation and test data for the proposed motor. [ABSTRACT FROM AUTHOR]

This paper comprehensively studies the electromagnetic performance of flux-reversal permanent-magnet (FRPM) machines with different consequent-pole PM (CPM) topologies. Four CPM topologies are first introduced and classified by different numbers of PM pieces and PM locations on stator teeth. Then, the distribution and working harmonics of air-gap flux density of each CPM topology are analyzed and compared, from which the CPM topology with the highest torque density is identified. The influence of critical design parameters on machine performance is also parametrically investigated. By comparing the torque performance of CPM topologies with their surface-mounted PM counterparts, the advantages of CPM topologies, i.e., torque improvement and magnet volume reduction, are clearly revealed. Four FRPM prototypes are manufactured and tested to verify the analyses. [ABSTRACT FROM AUTHOR]

This paper presents a novel consequent-pole hybrid brushless wound-rotor synchronous machine (CPH-BL-WRSM). The proposed machine employs permanent magnets (PMs) on the alternate poles of the salient pole rotor, which has considerably less magnet usage compared to the regular (PM) assisted synchronous machine. The proposed CPH-BL-WRSM offered the advantages of high starting torque, high torque density, and better performance under full-load conditions. The BL operation for the proposed machine is achieved by generating a composite magneto motive force (MMF) with a fundamental component and sub-harmonic component. The sub-harmonic component of the stator MMF is used for BL excitation of the rotor. The finite-element method was used to analyze the performance of the CPH-BL-WRSM in comparison with the performance of the existing BL-WRSM and regular PM-assisted BL-WRSM. Finally, a prototype of the CPH-BL-WRSM was manufactured and the experiment was conducted to demonstrate the performance of the proposed CPH-BL-WRSM. [ABSTRACT FROM AUTHOR]

The effects of multi-phase and multi-layer windings of the 12-slots 10-poles surface-mounted permanent magnet synchronous machines (SPMSMs) on eddy current losses in permanent magnets (PMs) are mainly investigated using the 3-D finite element analysis in this paper. Eddy current losses in PMs considering its axial segmentation are also analyzed. It is demonstrated that dual three-phase four-layer (DTP-FL) winding layout has the minimum value of eddy current losses in PMs, when segmentation number $N = 4$. It is because DTP-FL winding has smaller magnitude of high-order magnetomotive force harmonics relative to other four winding layouts. The average torque and torque ripple changing with multi-phase, multi-layer, and axial segmentation are also studied. Finally, the no-load and load experiment platform for an axial flux integrated-starter generator with DTP-FL winding and radial segmented PM are established in order to validate the proposed method under power generation mode. [ABSTRACT FROM AUTHOR]

The parallel hybrid excitation machine (PHEM) consists of axial parallel permanent magnet machine part and doubly salient electromagnetic machine part. The three-phase armature windings of two parts are connected in series. Based on the waveforms of back electromotive force, both sinusoidal and rectangular current excitations can be adopted in PHEM. The torque characteristics of PHEM drives with ideal sinusoidal and ideal rectangular current excitations are analyzed. The average torque versus armature current in brushless ac (BLAC) and brushless dc drives are comparatively analyzed. Furthermore, the torque and torque ripple versus current angle in some typical armature currents are investigated. Moreover, the speed and torque waveforms are given under the vector control and the current pulsewidth modulation control scheme. Finally, the experimental data of the target PHEM agree well with the simulation results. It is shown that in BLAC drives, the PHEM exhibits higher torque density with lower torque ripple. [ABSTRACT FROM AUTHOR]

A comprehensive description of a bearingless permanent magnet synchronous machine is presented including simulation, design, control and measurement focusing on a 1 kW/60,000 min-1 machine. A combined six-phase winding is used for the excitation of the two-pole motor field wave and the four-pole levitation field wave by applying two parallel three-phase current systems. The decomposition into the individually controllable current systems for motor torque and lateral rotor position control and the calculation of the relevant control parameters is explained. Measurements give an insight on the controlled motor performance. Thus, it is shown that the combination of torque and lateral force production with a single six-phase winding, fed by two three-phase inverters, not only leads to advantages in winding manufacturing but can be operated with a conventional field-oriented control also at high speed. [ABSTRACT FROM AUTHOR]

This paper adopts simple analytical modeling to investigate the contribution of air-gap field harmonics to the torque production in some three-phase, 12-slot/8-pole doubly salient synchronous reluctance machines (DSRMs) with both conventional and mutually coupled winding configurations. The air-gap flux density has been calculated based on the analytically obtained magnetomotive force and doubly salient air-gap permeance for both the double-layer and single-layer DSRMs with different winding configurations. Then, the contribution of different air-gap field harmonics to average torque and torque ripple can be investigated and validated by direct finite-element analyses. It has been found that in the DSRMs, the 10th-order harmonic in the double-layer conventional winding (DLC), the 4th-order harmonic in the double-layer mutually coupled winding (DLMC), the 7th-order harmonic in the single-layer conventional winding (SLC), and the 10th-order harmonic in the single-layer mutually coupled winding (SLMC) have the highest contribution to positive average torque and with positive influence on torque ripple reduction. However, the 2nd-order harmonic in the DLC, the 8th-order harmonic in the DLMC, the 5th-order harmonic in the SLC, and the 2nd-order harmonic in the SLMC machines mainly reduce the average torque. [ABSTRACT FROM AUTHOR]

This research proposes a novel low-voltage inverter-fed motor drive with variable parameters achieved through the independent armature winding for the automobile traction motor. The independent armature winding with low-voltage inverters can improve the total efficiency by reducing the converter losses. The inverters are able to change their connections to different coils groups of the armature winding in order to achieve the wide operating range. The voltage equation of each mode can be shown by using the transformation matrix when the winding connection is changed. Thus, the proposed motor is called the MATRIX motor. In this paper, the downsized model was designed to verify the principle. The principle model is able to achieve four motor parameters. It was confirmed that the principle model could extend the operating range and could achieve the high-efficiency driving in wide speed range. Furthermore, the novel winding reconfiguration method is proposed that not only avoids the surge voltage, but also compensates the torque reduction during the winding reconfigurations. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of concentrated winding configurations and stator core structures on torque performance of fractional-slot surface-mounted permanent magnet (SPM) machines. From analyzing the separated torque components of prototype SPM machines with 12-slot/10-pole (12S/10P) combination by frozen permeability (FP) method, it can be found that the torque ripple is closely related with local saturation in fully closed slot (FCS) machines. Besides, the heavier local saturation will also jeopardize the merit of using alternate teeth wound windings, such as obtaining higher average torque than electrical machines with all teeth wound windings. The further analysis of stator tooth relative permeability variation over one electrical period demonstrates that the major reason for torque ripple difference among these electrical machines with different stator topologies is the asymmetric saturation between the adjacent teeth. Both the subharmonic due to armature reaction (determined by winding connection and current value) and the asymmetry of stator core structure contribute to such asymmetric saturation. In order to more clearly verify this, the complementary slot/pole number combination (12S/14P) is also analyzed. The conclusion is effective for electrical machines with other slot/pole number combinations as well. Experiments have been carried out to validate the predictions. [ABSTRACT FROM PUBLISHER]

This paper presents a closed-form solution to optimize surface permanent magnet (PM) machines using concentrated windings. An analytical model is developed to predict the electromagnetic performances of fractional-slot PM machines. The model can be used to evaluate open-circuit magnetic field distribution with stator slotting effects, armature reaction field distributions, back-EMF waveform, winding inductance, cogging torque, electromagnetic ripple torque, efficiency, specific power, radial force density, and vibration mode order. Particle swarm optimization technique is applied to the proposed model in order to search for solutions that are a good compromise between conflicting objectives. The performances of the optimized machine are verified using finite element analysis. Finally, the analytical and finite element results have been validated with the experimental data, demonstrating a strong correlation between key machine parameters. [ABSTRACT FROM PUBLISHER]

In this paper, the torque production of fractional-slot concentrated-winding (FSCW) permanent-magnet synchronous machines (PMSMs) is analyzed from the perspective of the air-gap field harmonics modulation accounting for slotting effect. It is found that the average torque of FSCW PMSM is produced by both the principle of conventional PMSM and the magnetic gearing effect. A finite-element analysis (FEA) based equivalent current sheet model and harmonic restoration method is first used in FSCW PM machines with different slot–pole number combinations to quantify the respective contribution of the conventional PMSM and the magnetic gearing effect to the average torque. The influence of slot opening on the magnetic gearing effect, cogging torque, and torque ripple is analyzed. The results show that the magnetic gearing effect makes a nonignorable contribution to the average torque when a large slot opening stator is used. The expression of the gear ratio in FSCW PMSMs is derived. The influence of gear ratio on the contribution of the magnetic gearing effect to the total torque is investigated by FEA. The FEA-predicted torques are validated by experiments on the prototypes. [ABSTRACT FROM PUBLISHER]

Winding configurations that are applicable to a novel bearingless flux-switching permanent magnet motor with stacked structure are investigated, and one method to evaluate these winding configurations is also proposed in this paper. First, the motor structure and the influence of coil connections on torque and radial force are illustrated, and the fundamental radial force expressions of two diametrically opposite coils are derived. Afterward, two kinds of torque windings and four kinds of radial force windings for the motor are studied and the radial force models are derived accordingly. Following this, the radial force models are verified and the transient radial force and torque characteristics are investigated by finite element analysis. More importantly, an evaluation factor related to the winding copper losses is defined to evaluate the winding configurations. Finally, an optimal winding configuration is determined theoretically and a prototype motor is built to validate the effectiveness of the motor structure and the optimal winding configuration. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of the stator winding connection on the performance of a six-phase switched reluctance machine (SRM). Five winding connection types are proposed for the machine. Finite element analyses (FEAs) of flux distribution, output torque, and core losses are presented under single-phase and multiphase excitation for each connection and the results are used to compare the average torque and torque ripple ratio characteristics and to develop understanding of the respective contributions of mutual inductance in the torque development. Experimental tests on a six-phase conventional SRM verify the torque performance and mutual inductance effects of the different winding connections. An optimum winding configuration for a six-phase SRM is proposed. [ABSTRACT FROM AUTHOR]

The brushless doubly fed machine (BDFM) has been one of the key topics in the research of wind power generation. To improve the performances of the BDFM, a new permanent magnet (PM) brushless doubly fed generator (BDFG) with complementary structure is proposed in this paper. Compared with the traditional BDFM, there is an additional PM rotor providing excitation magnetic field for power and control windings. Benefiting from the absence of the exciting current and the excitation loss, the efficiency, and the power density may be increased. In order to solve a series of problems due to the introduction of PM rotor and the field modulation ring, the segmented structure is adopted. The improvement schemes are introduced in detail. Finally, the performances of the proposed BDFG are analyzed by the finite-element analysis and the results verify the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

A new cross-saturated torque model of the synchronous reluctance machine (SynRM) including a direct incorporation of cross-saturation effects is presented. Direct-quadrature (d-q axes) flux linkages for both saturation and cross-saturation conditions, obtained experimentally through current decay test using open winding fixed rotor method, are accurately curve-fitted and linearization between the two extremes yielding analytical functions for cross-coupled d-q axes flux linkages. These flux linkages are used to achieve a cross-saturated flux linkage-based torque model for highly utilized SynRM. The accuracy of the developed torque model is evaluated by comparing with the experimentally measured torque of a 5.5 kW SynRM in a dynamometer test bench which also measures and account for the effect of iron losses. The close similarity of the experimental results with the developed model proves the accuracy of the model and its suitability for direct incorporation in control algorithms of advanced SynRM drives without the use of look-up tables. [ABSTRACT FROM AUTHOR]

In this study, an air core spherical motor comprising a two pole permanent magnet rotor with 8 mm diameter and a multipole stator is designed by considering the ease of manufacturing priorities. Stator winding dimensions are calculated in a way to give maximum torque to the rotor analytically. Magnetic field distribution and torque values are calculated analytically. Stator coils in the yoke made from Delrin are positioned in proper values. Spherical motor with three poles stator and two poles rotor can move 44° up and down in 360° azimuthal angles without direct rotational movement in an open loop system and it is suitable to use in cascade in a robotic system. [ABSTRACT FROM AUTHOR]

This paper studies the postfault control of a nine-phase six-terminal induction machine (IM) during single open-line fault, which was recently proposed for high-power medium-voltage applications as a promising alternative to conventional six-phase IMs. The required optimal reference currents to provide prefault loading conditions under one-line open are derived using the two most common optimization criteria employed in multiphase drives, namely, maximum torque and minimum loss modes. A postfault controller, based on conventional decoupling Clarke's transformation, is then used to ensure the same controller structure under all conditions. Consequently, the machine characteristic curves, achievable torque, and stator copper losses under these different modes are compared. A comparison with a conventional asymmetrical six-phase winding is also given. A 1.5-Hp prototype IM is used for experimental verification. [ABSTRACT FROM PUBLISHER]

In a winding system, it is very important to control the tension precisely. Based on the process of rewinding and unwinding, a sensorless tension control method with PI parameters of adaptive speed controllers is proposed in this paper. According to the principle of torque balance, a tension observer is designed to replace the tension sensor, and the observed value instead of the measured value of tension is used as feedback. Then the measurement delay caused by tension sensor is reduced. For the time-variable inertia, Landau discrete-time recursive algorithm is used to estimate the inertias of the rewind and unwind motors. Moreover, the estimated inertias are used to adjust the PI parameters of the speed controllers. As the tension control system has the ability to adapt to the change of inertia, its dynamic performance is improved to some extent. In addition, the proposed sensorless tension control method is simple and easy to implement, which only uses the current and speed signals of the motors without any additional hardware needed. At last, the feasibility and effectiveness of the proposed method are verified by the experimental results. [ABSTRACT FROM AUTHOR]

This paper presents a new axial flux permanent magnet machine, named ring winding axial flux machine (AFM). The ring winding AFM (RWAFM) takes the advantage of segmented stator of yokeless and segmented armature topology with those of decoupled phases and ring winding of transverse flux topology. In this paper, the geometry of the RWAFM is introduced in detail. Furthermore, the working principle and torque production theory are discussed. To validate the concept and confirm manufacturability of the proposed topology, a prototype is fabricated. The performance of the RWAFM is studied through experimental tests, 3-D finite-element simulations, and analytical discussions. [ABSTRACT FROM PUBLISHER]

Because single-phase dc-excited flux switching machines (DCFSMs) consist of only copper windings and iron cores, they have great potential in low-cost and high-speed applications, such as home appliances. However, similar to other types of single-phase ac machines, single-phase DCFSMs have insufficient initial torque at some rotor positions. A novel single-phase, eight-slot, four-pole DCFSM design is presented in this paper. The key feature of this design is the enhancement of reluctance torque at positions where the machine cannot deliver sufficient initial torque output. This is accomplished by modifying the outline of a section of the rotor. Consequently, the machine has a two-layer rotor structure along the axial direction. The proposed design is validated experimentally using a prototype. The results show that the machine can start from any rotor positions with initial torque higher than 50% of the rated output torque. [ABSTRACT FROM AUTHOR]

In this paper, the characteristics of interior permanent magnet synchronous machine (IPMSM) with concentrated windings are evaluated for three different rotor geometries. The reference machine is a fractional horsepower IPMSM with single-layer magnets (1-layered IPMSM). The maximum output power of the machine is 820 W. Based on the electrical properties and machine cost of the reference machine, IPMSM with two different rotor geometries are designed. The first one is an IPMSM with v-shaped magnets and the second one is an IPMSM with double-layer magnets topology (2-layered IPMSM). The machines are compared in two operating points: one in the base speed area and one in the field weakening range. The focus of the machine comparison is the parasitic effects due to the nonsinusoidal rotor field, e.g., back-EMF harmonics, torque harmonics, radial force densities, and iron losses. [ABSTRACT FROM PUBLISHER]