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This article proposes a multiobjective optimization design framework for a double stator brushless hybrid excitation motor (DSBHEM) to provide high torque, wide flux regulation ability and low torque ripple. The design variables are divided into sensitive level and insensitive level by sensitivity analysis. The response surface model (RSM) and nondominated sorting genetic algorithm 2 (NSGA2) are organically combined to generate a set of Pareto solutions for the sensitive level variables, from which the optimal values of the sensitive level variables are obtained. In addition, the optimal values of insensitive variables are obtained through single parameter scanning optimization, and a set of final optimal design variables are obtained. The electromagnetic performance of the initial design and the optimal design are compared with finite element analysis. Finally, a prototype is manufactured to verify the proposed concepts. [ABSTRACT FROM AUTHOR]

This article presents an accurate analytical model (AM) for synchronous reluctance machine (SynRM) that incorporates the effect of stator slots on the air gap flux density and torque waveforms. From the formulation of magnetic potential in the air gap for both the stator and rotor, the flux density is obtained, considering the first harmonic of the flux density and the electric loading, the average torque is calculated using the Lorentz’s force. The ripple torque is obtained from the energy stored in magnetic circuit. The method is developed for a rotor with one flux barrier per pole and then extended to a larger number of barriers. To validate the results obtained by the AM proposed finite element analysis have been carried out. Several comparisons have been derived considering different rotor positions as well as different harmonic orders, and the pros and cons of the method are highlighted. The model performs fast and can predict results with high accuracy, and can be adopted to speed up the preliminary design and optimizations of this type of motors, with respect to finite element. In addition, from the analytical expressions it is possible to obtain all the correlations between electrical, magnetic, and geometrical characteristics of the machine, with the advantage of enabling a faster machine design. [ABSTRACT FROM AUTHOR]

Synchronous reluctance motors (SynRMs) with four layers of flux barriers are currently in practical use as high-efficiency motors for industrial applications. While SynRMs have higher efficiency than induction motors, they have a high torque ripple. In this study, an asymmetric rotor structure was designed to reduce the torque ripple of the four-layer SynRM, considering the mechanical strength. Two rotor structures with different flux barrier angles were combined in the stacking direction, and the ratio of the combination was optimized by finite element analysis. In addition, prototypes of the initial structure and proposed asymmetric structure were manufactured, and their torque and efficiency characteristics were measured. The experimental results show that the proposed asymmetric structure can reduce the torque ripple while maintaining the basic characteristics such as average torque and efficiency. [ABSTRACT FROM AUTHOR]

Vernier reluctance machine (VRM) with dc field coils in stator is a competitive rare-earth-free design for variable-speed industrial applications due to its robust structure and controllable excitation, while its torque density is relatively disadvantageous. To address this issue, this article proposes a new armature winding design method for VRM with dc field coils across two stator teeth. The key is to break the traditional winding design principle based on the flux modulation effect of fundamental dc field harmonic, and instead, reconstruct a novel harmonic winding to enhance the utilization factor of the modulated high-order dc field harmonics arising from the unique magnetomotive force distribution of dc field coils across two stator teeth. By this means, the torque density can be improved by 75.6% against the existing poor counterpart. In this article, the machine structure and operation principle are introduced, with emphasis on the high-order dc field harmonics distribution rule and its influence on the armature winding design. By finite element design and optimization, a comparative study is performed to evaluate the electromagnetic performance of VRMs using two different winding configurations with variable slot pole combinations. A prototype is fabricated and tested, and the results agree well with finite element analysis, which verifies the feasibility and advantages of the proposed winding design method. [ABSTRACT FROM AUTHOR]

A new partitioned stator field modulation machine (PSFMM) with H-shape permanent magnet (HPM) excitation (HPM-PSFMM) is proposed, which is evolved from the conventional flux-switching machine (FSM) and flux-reversal machine (FRM). The proposed HPM-PSFMM combines the merits of high reliability and good heat dissipation characteristic. In addition, it exhibits high torque production with low torque ripple. Based on the theory of electrical machine operation, the FSM and FRM can be transformed into PSFMM with interior permanent magnet (IPM) and surface-mounted PM (SPM) excitation by changing the position of PM excitation, respectively. It benefits to improve space utilization and increase slot area for a large number of armature windings. For reducing the flux leakage and enhancing the flux density in air gaps, the IPM and SPM excitation are combined into HPM excitation. The iron-pole rotor between the inner and outer stators acts the role of modulator to modulate the magnetic field excited by HPM excitation to couple with the armature reaction for converting electromechanical energy. The evolution process, operating principle, and key design parameters of the proposed HPM-PSFMM are presented. Finally, using the finite element analysis (FEA), it can be proven that the proposed HPM-PSFMM has the merits of high torque production, low flux leakage, low total harmonic distortion (THD), and low torque ripple when compared to other stator-PM machines, which is a desirable choice for high stability applications. [ABSTRACT FROM AUTHOR]

The magnetic field distribution in the air gap is of great importance in the design of rotary machines. In this article, an efficient analytical method is presented, which is capable of plotting the air-gap flux density waveform of induction machines (IMs) less time-consuming than the finite element method (FEM) does. The proposed method, based on the product of the current linkage waveform and the permeance waveform, utilizes the calculations of the steady-state equivalent circuit to ensure the accuracy and an equivalent air-gap reluctance model to take into account both the slot opening effect and the rotor movement. The method is tested on a general IM with different load cases and different design parameters, and the results are compared to the FEM calculations. It can be concluded that the proposed analytical method is an efficient option in the motor design to investigate the influence of the parameters on the flux density distribution. [ABSTRACT FROM AUTHOR]

This paper presents an analytical approach to determine the air-gap magnetic field and the winding inductance in the brushless doubly-fed reluctance machine (BDFRM) with flux barriers. By dividing one flux guide layer into several segments, a calculus method based on magnetic circuit analysis is developed and specific analytical expression of the air-gap flux density is rigorously derived. Then, the included angle between fundamental components with the same pole pairs is also discussed. Based on the air-gap flux density distribution, the inductance expressions between different windings are also presented. Three kinds of finite element analysis models are established and studied. As a result, the accuracy of the analytical model can be verified by simulations and experimental data from an existing BDFRM prototype. [ABSTRACT FROM AUTHOR]

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

Special attention has been paid to two-phase switched reluctance motors (SRMs) as they have fewer power electronics components compared to three- or multi-phase ones. However, their main drawbacks are the lack of starting torque and a predetermined direction of rotation. This paper proposes a new self-starting technique for two-phase SRMs, which has superiorities over the previous approaches. In the proposed topology, the flux paths are shorter, and thus the required magnetomotive force is smaller, which reduces losses. The design procedure is explained. Two- and three-dimensional finite element method (FEM) is employed in the analysis. Also, the motor is prototyped, and two test setups for torque-angle measurement and control study are used. The dynamic behavior of the motor is studied applying single-pulse control and current hysteresis control strategies. The experimental results confirm the results obtained by FEM. Both simulation and experiment results confirm that the proposed topology offers higher efficiency, higher mean torque, and better dynamic behavior compared to two conventional SRMs. [ABSTRACT FROM AUTHOR]

In this paper, a novel six-phase outer rotor induction motor equipped with pseudo-concentrated windings is introduced as a robust, reliable, and low-cost solution. Multiple aspects of the proposed motor structure have been investigated such as a design algorithm and an analytical modeling based on the modified winding function considering the skew effect. The effect of using variable number of turns for the coils has been examined on the pseudo-concentrated windings. An appropriate optimization problem has been also defined to maximize the power factor and efficiency and to minimize the output torque ripple. The designed motor has been fabricated to verify the accuracy of the design procedure with an analytical model and a finite element analysis. Experimental results show superior performances for the designed motor. [ABSTRACT FROM AUTHOR]

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

In this article, a new dual-winding dual-flux-concentrated magnetic-field-modulated brushless compound-structure machine (DDMFM-BCSM) is proposed by combining the magnetic-field modulated brushless dual-rotor machine (MFM-BDRM) and permanent magnet synchronous machine (PMSM) into one. Proposed machine has two sets of windings in stator slots and spoke-type PMs on dual rotors. Besides, there are flux barriers on the inner rotor to improve the performance of MFM-BDRM part. Based on magnetic field modulation principle, the main harmonics of the flux density in inner and outer air gap are calculated by analytical method and simulated by finite element method (FEM). The performance of the proposed machine, including MFM-BDRM part, PMSM part, and the whole DDMFM-BCSM, is analyzed. In order to analyze the influence of flux barriers on the performance of DDMFM-BCSM, a DDMFM-BCSM without flux barriers is designed to compare their performance, including torque, loss, and power factor. [ABSTRACT FROM AUTHOR]

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 Nd-Fe-B magnet motor and were able to quantify the base frequency, the maximum torque, and the minimum stack length of core for a distributed-winding motor with high accuracy without having to rely on FEA. The FEA and measurement results demonstrated the validity of the proposed approach for the fabricated distributed-winding PM motor. [ABSTRACT FROM AUTHOR]

The main idea of this paper is to offer a continuous C-cores unique configuration for switched reluctance motor (SRM) and to present an analytical model for its analysis. The advantages of this structure are having a short path for the main part of the magnetic flux, resulting in less core losses and as well as less negative torque. On the other hand, there is less leakage flux in the proposed structure. Another advantage of this structure is that it has a high mean torque compared to conventional structures, so that this increase in mean torque also increases a small amount of torque ripple, which is negligible. However, power density at a constant volume increases relatively much. The proposed SRM is analyzed by the finite element method (FEM) and by employing a magnetic flux density pattern and magnetic fluxes path, its magnetic equivalent circuit (MEC) is obtained. In this MEC model, the main fluxes and leakage fluxes are fully modeled. After its complete analysis, electromagnetics torque, inductance, flux-linkage, mean torque, and peak torque are evaluated. Static and dynamic performances are then determined. Finally, the proposed SRM was prototyped and tested. The experimental results consisting of static torque, flux-linkage, voltage, and current waveforms and input power are compared with the corresponding results in the MEC model and FEM. The comparisons verify the accuracy and validity of the introduced analytical model. Besides, static torque, flux-linkage characteristics, and dynamic performance at a nominal speed of 1000 rpm and the current chopping control mode with chopping 5A under the load of the proposed SRM are compared with the conventional SRM and its merits are observed. [ABSTRACT FROM AUTHOR]

This paper presents a dynamic thermal model which predicts the winding temperature of electrical machines at steady-state and transient conditions where windings are used in integrated battery chargers (IBCs) for DC charging in a stationary position. Using winding in high current charging process causes rising winding temperature which affects insulation life. Switched reluctance machines are a proper choice for using in electric vehicles (EVs) because of their advantages such as simple and sturdy structures. IBCs can reduce volume and weight of EVs and total cost is diminished because of integration. The analytical thermal model proposed in this paper can calculates the winding temperature in balanced and unbalanced currents injection because of the phase inductance in each rotor angle is distinct, so current excitation in each phase should be different for obtaining zero total torque and keeping rotor in a stationary position, also a reduced-order model is proposed with minor impact on the accuracy of the model. Special attention has been paid to monitor the winding temperature with considering the motor lifetime in DC charging mode, this view has not been addressed in IBCs before. The proposed model is then validated against experimental results and 3D finite element method. [ABSTRACT FROM AUTHOR]

In this article, a variable flux reluctance machine (VFRM) with dc field excitation and modular structure is proposed and it exhibits controllable flux, simplified manufacture, better fault tolerant capability, and potentially reduced material consumption. Its operational theory is illustrated by using flux modulation principles, and the working harmonics considering the modular structure are analyzed. Besides, the winding factors of modular VFRM are derived considering the flux gap width. The parameters are optimized by two-dimensional finite element method to maximize the back electromotive force (back-EMF) and the ratio of phase self-inductance to mutual inductance. Moreover, the electromagnetic performance including open circuit air-gap flux distributions, open circuit air-gap flux densities, flux linkage, back-EMF, inductance of armature windings, output characteristics, loss, power factor, and efficiency-map are compared for 12s10r and 12s14r nonmodular and modular VFRM. Additionally, the fault including short circuit and open circuit fault are analyzed. Finally, a modular 12s14r VFRM prototype is manufactured and tested to validate the theoretical and finite-element analyses. [ABSTRACT FROM AUTHOR]

In this article, a novel dual-consequent-pole transverse flux motor and its analytical model are proposed. Differ from existed transverse flux machines, the proposed motor owns core-tooth-to-magnet types of the consequent-pole configuration on both stator and rotor. This unique motor configuration improves the no-load permanent magnet flux linkage interlinking with armature winding, thus leading to an enhanced torque density. The structure and working principle of the proposed motor are introduced as the first half part. Then, based on the combination of equivalent magnetic circuit method and subdomain method, an analytical modeling method is proposed to estimate the electromagnetic performance of the proposed motor. The parameters of the equivalent magnetic circuit model, e.g., the magnetomotive force and reluctances are calculated based on the subdomain model technique, considering the influence of the cores’ saturation and the axial end effect during calculation. Based on the magnetic field distribution result, the electromagnetic performance is estimated. The analytical results are verified by both the finite-element method and the prototype experiment. [ABSTRACT FROM AUTHOR]

High-speed switched reluctance machines (SRMs) have been a timely topic recently. However, for ultrahigh-speed SRMs over 100,000 rpm, the acoustic noise is a significant issue in many applications such as high speed spindles, compressors/ turbochargers, flywheels, and etc. In this article, a multiphysics acoustic modeling of ultrahigh-speed SRMs is presented based on finite element analysis (FEA). First, a three-dimensional electromagnetic FEA is conducted to calculate the radial force on the stator teeth. Then, a modal analysis and a harmonic response analysis are shown in the frequency domain to estimate the natural frequencies and vibration of the whole motor. An acoustic response analysis is done to estimate the sound pressure level (SPL) using the superposition of the surface vibration. To verify the model, experiments are done to measure and compare the natural frequencies and the SPL of a 4/2 ultrahigh-speed SRM at 100,000 rpm. The results show that the SPL of the motor is as high as 115 dB at 10 mm away from the motor, which matches the simulation result (113 dB) well. The impact of the bearing is proven to be negligible compared with the noise generated by the radial force. Finally, a parametric study example of using the proposed model to guide the design of SRMs has been conducted. It is shown that “hot dog” shaped motors have less noise than “pancake” shaped motors under the same motor volume, speed, and power. [ABSTRACT FROM AUTHOR]

This article proposes an improved analytical method for accurate evaluation of flux-linkage characteristics for a given switched reluctance machine (SRM). Initially, air-gap inductance is calculated using an approximated analytical method, which incorporates the effect of fringing fluxes. Then, precepts of a conventional method are used to compute these characteristics under saturation, with a proposed new analytical model for nonuniform flux distribution in stator and rotor poles. Finally, for error quantification, these characteristics are benchmarked against those from a standard finite element analysis (FEA) based software. Both mean and standard deviation of the estimation errors are presented to quantify estimation accuracy. To establish its general validity, these characteristics are evaluated using the proposed method for six SRMs of different geometries and compared with those obtained from FEA. For further benchmarking, speed-torque characteristics obtained from the proposed method and FEA are presented and compared. Finally, both flux-linkage and torque-speed data are experimentally obtained from a 5 kW, 270 V, 12 000 r/min, 6/4 SRM and presented for validating the accuracy of the proposed method. [ABSTRACT FROM AUTHOR]

The second harmonic current injection method is recently developed to enhance the torque density of variable flux reluctance machines (VFRMs). This article investigates the feasibility and effectiveness of the second harmonic current injection method in VFRMs with different stator/rotor pole combinations. By using magnetic gearing effect, it is found that the second harmonic injection method can only be applied to the 6j/(6i ± 2)j (i, j = 0, 1, 2…) stator/rotor pole VFRMs for the torque density enhancement. For the other stator/rotor pole combinations, the second harmonic current has no contribution in average torque production but only leads to excessive torque ripple. Further, by using global optimization method and finite element analysis, 6/8 stator/rotor pole combination is proved to be the optimal stator/rotor pole combination for 6-stator-slots VFRMs with the second harmonic current injection method, being able to exceed the maximal torque density of conventional VFRMs by 12% at a fixed copper loss. [ABSTRACT FROM AUTHOR]

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

This article develops a modified dynamic reluctance mesh (DRM) method that can be utilized to calculate and analyze the magnetic field of the iron-cored tiered-type permanent magnet spherical motor (T-PMSpM) effectively and efficiently, with the multi-degree-of-freedom (multi-DOF) movements taken into account. According to the structural characteristic of the iron-cored T-PMSpM, the tilting function part, including the tilting stator and rotor, is equivalent to a dynamic lumped-parameter magnetic network model. Besides, the magnetic saturation phenomenon of the iron materials is also considered. The DRM results of magnetic field distribution, flux linkage and back electromotive force (EMF) show a good agreement with the three-dimensional finite-element method results. For further verification, a prototype motor of the iron-cored T-PMSpM has been manufactured. The back EMF curves with different rotor tilting positions are measured by experiments and compared with the calculated results. [ABSTRACT FROM AUTHOR]

A systematic approach based on a novel space-shifted three-layer winding (SSTLW) to eliminate both the sub- and superharmonics of fractional slot concentrated winding ac machines is presented. In this proposed three-layer fractional slot winding, the number of turns in one layer and the relative positions of other two layers are optimized to cancel subharmonics. The cancellation of superharmonics is achieved through series connection of two SSTLWs through effective doubling of the number of slots. The cancellation of the dominant sub- and superharmonics using this approach leads to reducing the total harmonic distortion, torque ripple, PM eddy current loss, and rotor core loss, while simultaneously improving power factor and saliency ratio. The proposed design methodology and ensuring improvements have been validated through finite element analysis for the widely used 12-slot/10-pole and 18-slot/14-pole permanent magnet synchronous machine (PMSM) configurations. A prototype three-layer winding is built for a 10-pole PMSM to validate the simulation results experimentally. [ABSTRACT FROM AUTHOR]

Phase inductance is a key parameter in the design of switched reluctance machines (SRMs) because the torque, torque ripple, losses, and the dynamics of phase voltages and currents are related to the phase inductance. Therefore, accurate calculation of the inductance profile of an SRM is important in determining the SRM behavior. Instead of using the time-consuming finite element analyses (FEAs), or the analytical methods that require prior knowledge of flux linkage from either an FEA simulation or an experimental test such as the curve fitting and flux path based methods, this paper proposes a fast and accurate analytical approach to determine the phase inductance of an SRM with any common topologies, dimensions, and phase currents at any rotor position. In the proposed approach, the magnetic field distribution and the permeance parameters in the air region are first determined by solving the partial differential equations of magnetic potentials based on Maxwell's equations. The air-region permeance parameters are then substituted into a magnetic circuit network to include the impact of the saturation effects of steel on the phase inductance profile. The agreement between the results of the proposed analytical method and two/three-dimensional FEAs and experimental results validates the analysis. [ABSTRACT FROM AUTHOR]

A novel 8/10 two-phase switched reluctance motor is proposed. Thanks to this unique design, the flux paths are shortened, resulting in lower magnetomotive force requirements. There is no negative torque, bringing a higher total torque. The space is more effectively utilized to provide a higher torque density. Flux reversals in the iron cores are reduced, causing a significantly lower loss. The associated conceptual diagrams, optimized design procedures, detailed flux study, and loss analysis are presented. The proposed motor is compared with two existing 9/12 and 6/10 switched reluctance motor in terms of topology advantages, peak and average torques, torque density, core losses, etc. Moreover, a new efficiency index is introduced to more reasonably perform comparisons. Furthermore, finite element method is employed in the investigations. Finally, the motor is prototyped whose experimental results including torque-angle measurements and open-loop control confirm the novelty and superiorities of the proposed motor over the existing ones. [ABSTRACT FROM AUTHOR]

A criteria to design the rotor of multi flux-barrier synchronous reluctance (REL) machines is proposed. In particular, the focus will be on the proper design of flux-barriers geometry. An analytical model is adopted to compute the impact of the rotor flux-barriers on the torque, focusing on the torque ripple. Thanks to proper assumptions, the analytical model is simplified so as to highlight the main causes of torque ripple. Such an analytical model allows to derive the angles of the flux-barrier ends corresponding to the minimum torque ripple in a closed form. This result has never been presented in the past literature and it represents a useful tool as far as the motor design is concerned. Rotors with one, two, and three flux-barriers per rotor pole are taken into account. However, the advantageous analytical model can be extended to any number of flux-barriers per pole. Some examples referring to four-pole synchronous REL machines with different numbers of stator slots are investigated and illustrated. The results are compared with a full-featured analytical model and validated through finite element simulations. [ABSTRACT FROM AUTHOR]

This paper investigates a novel three-phase doubly salient permanent magnet (DSPM) motor. Because of the adoption of Π-shaped stator iron core segments, the asymmetrical magnetic circuit among different phases occurring in conventional DSPM motors with E-shaped stator iron core segments can be avoided, so that balanced and sinusoidal three-phase PM flux linkage and no-load electromotive force (EMF) can be achieved. First, based on a 12/7 stator/rotor pole combination, the operation principle of Π-core DSPM motor is discussed using the least magnetic reluctance principle. Then, the general airgap field modulation theory is extended to the Π-core DSPM motor for explaining its operation principle further and armature winding connection. The finite element analysis is used to validate theoretical analysis, as well as to calculate its electromagnetic performances. The results show that the 12/7-pole Π-core DSPM motor possesses higher average torque output capability and lower torque ripple compared with the 12/8-pole E-core counterpart. Finally, a 12/7-pole Π-core DSPM motor is built and tested so as to experimentally verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

Linear switched reluctance motors (LSRMs) provide an alternative to linear induction motor and linear permanent magnet motor in both vertical and horizontal propulsion applications. This paper attempts to develop a unitized design method of a segmental secondary LSRM, which is characterized by a modular magnetic circuit structure and the independent operation of multimover units. The developed design method is directly performed in linear domain without transforming it to a rotary SRM, which complies with the essential natures of the segmental secondary LSRM, showing that it is capable of delivering more power at the same dimensions compared to the conventional tooth type LSRM. Further, the sensitivity analysis of the critical geometric parameters is performed, and the guidelines for selection of the best dimension parameters are given. Finally, the three-phase and four-phase LSRMs are designed and prototyped, respectively with a 1-m long stator. The experimental results validate the design procedures and analysis above. [ABSTRACT FROM AUTHOR]

This paper analyzes the flux characteristics and normal force of the double-sided switched reluctance linear machine (SRLM) under the asymmetric air gap. The magnetic equivalent circuit (MEC) of the machine and the details of the flux paths configuration at six distinct mover positions under the asymmetric air gap are included. Then, six special mover position magnetization curves are calculated by solving the MEC with the method of Gauss–Seidel. The magnetic flux-linkage model and thrust model based on six distinct mover positions are established by analytical polynomial. Three-dimensional (3-D) finite-element method (FEM) simulation and the experimental study with the prototype hardware are carried out to validate the accuracy of the MEC model calculated for the flux linkage and normal force. The six distinct mover positions flux linkage and normal force calculated by the MEC are consistent with the 3-D FEM calculated data and experimental data. It indicates that the proposed method to calculate the flux linkage and the normal force is feasible and effective. The dynamic analysis is also conducted. The simulated phase current waveforms are also consistent with the experimental results. It indicates that the presented method can be used to simulate the phase current under the asymmetry air gap effectively. The normal force under different asymmetry rates is analyzed, which provides the theoretical basis for reducing the unbalanced force of the double-sided SRLM. [ABSTRACT FROM AUTHOR]

The recent novel dc-biased sinusoidal current reluctance machines (dc-biased VRMs) adopt a doubly salient structure and concentrated windings, which is similar to that of switched reluctance machines (SRMs). The special point is that the phase current is in the form of an ac component superimposed with a dc component. Some literary works show that these machines would have better performance than the existing SRMs and variable flux reluctance machines. In this paper, the slot/pole combinations and winding configurations of the dc-biased VRMs are deeply investigated. First, relationships among slots/poles are given based on the operation principles. Then, several feasible slot combinations are obtained, and the electromagnetic performances including magnetizing inductance, virtual back electromotive force, torque quality, and losses are compared by the finite element analysis. Finally, the correctness of the proposed analysis is validated by the experiment on two 12/10 prototypes. [ABSTRACT FROM AUTHOR]

This paper presents the design and experimental validation of a synchronous reluctance motor (SynRM) using a multilayer (ML) ac winding that meets the ultra-premium/IE5 class efficiency requirement. Compared to conventional double-layer ac windings, the ML winding yields a more sinusoidal stator magnetomotive force (MMF) with a shorter end-turn length. The ML winding is characterized using an analytical stator MMF model with verification against finite element analysis (FEA). The proposed winding configuration is optimized under a given design benchmark. The multi-barrier rotor design is also optimized based on FEA using a genetic algorithm. The performance of the designed ML-SynRM is compared against a commercial premium efficiency induction motor and a conventionally wound SynRM for the same standard frame and cooling type. Results show significant efficiency gain with SynRM designs, and also, the designed ML-SynRM yields lower torque ripple with an improved power factor compared to the conventional SynRM. The prototype ML-SynRM is built, and its simulation results are experimentally validated against the benchmark including their performances at a thermal steady state. [ABSTRACT FROM AUTHOR]

This paper proposed a varying magnetic network modeling method of dual-rotor permanent magnet reluctance (DRPMR) machines based on magnetic circuits considering possible saturation and nonlinearity according to the physical structure, which is put forward to obtain the accurate inductance characteristics of the proposed machine. The feasibility of this analytical model is confirmed by the finite element method. Moreover, experiments are designed to validate the analytical results. It indicates that the analytical inductance characteristics of the DRPMR machine have good agreements with the experimental results. [ABSTRACT FROM AUTHOR]

DC-biased sinusoidal current vernier reluctance machines (dc-biased VRMs) have a doubly salient structure, and their phase currents contain an alternating current (ac) component and a direct current (dc) component. Hence, their main features are one set of concentrated windings compared with variable flux reluctance machines, low vibration and noise due to smooth current, compared with switched reluctance machines, and robust rotor structure. Besides, its achievable high slot fill factor can improve the torque density further. In this paper, based on the flux modulation principles, the torque production mechanism of dc-biased VRMs is analyzed, and two slot combinations of 12/8 and 12/10 are proposed. First, the machine topology and inverter main circuit are illustrated. Second, the torque production mechanism is explained. Furthermore, the inductance characteristic, optimal current configuration for maximum torque and lowest torque ripple are analyzed theoretically and by the finite-element analysis. Finally, one prototype was designed and built, and the proposed analysis is validated by the experimental results. [ABSTRACT FROM AUTHOR]

Linear switched-reluctance motor (LSRM) is investigated and proved to be an alternative for direct linear driving systems, especially for long-distance transportation applications, such as vertical elevator driving motor. This paper presents the design, sensitivity analysis, and optimization of a toroidally wound mover LSRM with segmental stator. The presented LSRM has much higher copper utilization ratio and flux carrying capability than the conventional LSRM for vertical linear propulsion application. The features of motor performance influenced by various geometrical parameters are described using magnetic circuit and finite element analysis to give the guidelines for selecting the reasonable range of those parameters of this kind of machine. Furthermore, an optimization procedure is performed to obtain the optimal machine dimensions considering active payload ratio and force ripples. Finally, the experimental results from the prototype validate the design procedures and analysis above. [ABSTRACT FROM PUBLISHER]

A switched reluctance motor (SRM) with 12/10 poles is investigated in this paper. Compared with the conventional SRMs with single mode, the machine is not only able to be worked as a six-phase motor but also could be used as a three-phase motor, which is thus named multimode SRM (MMSRM). The primary dimensions of the stator and rotor cores are calculated by considering it as a six-phase SRM with long magnetic paths, and the performances of three-phase mode with short magnetic paths are used to test the parameters. The arcs of stator and rotor pole are treated as the optimization objects to minimize torque ripple and copper loss per torque and maximize torque per ampere of the MMSRM. A function is selected to solve the multiobjective problem and the final values of arcs of stator and rotor pole are determined based on the results of finite-element method. The effects of arcs of stator and rotor pole on electromagnetic performances of MMSRM are discussed independently, and a prototype is manufactured to test the simulations. A good agreement between the simulated and measured results verifies the validity of the analytical method and results. [ABSTRACT FROM AUTHOR]

This paper deals with an analytical model of reluctance synchronous motor, able to consider both stator slotting effect and magnetic saturation in the stator and rotor iron paths. It joints the field distribution at the air gap to a lumped-parameter magnetic network. Local saturation factors are defined so as to adjust the flux-density distribution. The analytical approach exhibits great potentiality, since it is a formulation based on an harmonic study, and it is easily adaptable to any motor geometries. As an example, 36-slot 4-pole machine is analyzed, considering three flux barriers per pole. Finite element analysis confirms the results achieved by means of the analytical model. [ABSTRACT FROM PUBLISHER]

This paper presents a new switched reluctance motor (SRM) with wide speed range for the application of electric vehicles. It has an in-wheel structure for direct drive and multiple teeth per stator pole to enhance output torque. Also, the number of rotor poles is more than that of stator teeth. A 6/16 three-phase in-wheel SRM with the concepts of multi-teeth per stator pole and more rotor poles than stator teeth has been proposed for analysis. The torque performance of the topology with multi-teeth per stator pole is proven by theoretical analysis. Moreover, a new design formula is introduced for a novel combination of stator and rotor poles. The parameters of the motor are optimized by genetic algorithm method for the maximum torque output. Then the torque performance is computed by finite-element method (FEM) and compared with its counterparts, including three-phase 6/8 and 6/10 SRMs. The FEM results exhibit higher torque density for the proposed topology. [ABSTRACT FROM AUTHOR]

An analytical calculation of the winding flux linkages and torque is proposed for fully pitched mutual coupled switched reluctance motors to develop a machine model without using numerical methods. The proposed technique is not empirical and does not require any finite-element analysis (FEA). The design parameters and the material properties of the machine are the only inputs to the model, which can predict the winding flux linkages and torque at any phase currents and rotor positions. The model is applicable for the rotor positions where the stator and rotor poles overlap. Initial assumptions and then the step-by-step procedure for flux linkage, co-energy, and torque calculations are provided. The flux linkages and torque predicted through the proposed modeling technique are compared with the FEA results. Finally, experimental results of flux linkage and torque are provided to verify the accuracy of the proposed modeling technique. [ABSTRACT FROM AUTHOR]

A reciprocating single-phase tubular switched reluctance linear launcher (TSRLL) with a short stroke is presented in this paper. The parametric design of this launcher is achieved based on finite-element method (FEM). By using the finite-element (FE) software FLUX, the 2-D and 3-D electromagnetic analyses of this launcher are carried out, respectively. The characteristic curves of position-current-flux linkage are analyzed by the 2-D and 3-D FEM. The prototype tests are conducted to verify the FE analyses. The static tests results show that the 3-D FE calculated results are more precise than the 2-D FE calculated results, and they coincide well with prototype static test results. The effectiveness of the FE model for the TSRLL is further testified by the results of prototype dynamic tests. Finally, some analyses on sensitivity parameters are conducted to further improve the performance of the TSRLL. [ABSTRACT FROM PUBLISHER]

In this paper, a harmonic field current injection method is proposed for torque ripple reduction in 6-stator/4-rotor-pole (6s/4r) variable flux reluctance machines (VFRMs). Initially, the torque production of VFRM is analyzed based on an analytical torque model and harmonic analysis. The torque ripple of 6s/4r VFRM is found to have multiples of third harmonics. Then, one finite-element analysis (FEA)-based and one analytical equation-based method are developed to calculate the magnitude of the injected harmonic current. Both methods are proved to be effective in torque ripple reduction. Finally, the influence of the inductance mismatch on the proposed method is investigated. It shows that the torque ripple reduction performance is not affected much unless the fundamental component of nominal inductance is underestimated. The feasibility and effectiveness of the proposed methods are validated by both 2-D FEA and experimental test. [ABSTRACT FROM AUTHOR]

This paper deals with the nonlinear analytical harmonic modeling (HM) of three phases, and 6/4 conventional switched reluctance machine (SRM). The proposed model consists in computing magnetic field distribution and electromagnetic performances of an SRM with conventional winding. Because an SRM has inherently nonlinear characteristics, the analytical subdomain model that does not take into account the saturation has a limited accuracy. This is due to the assumption of infinite tooth permeability. The new analytical model (AM) based on the HM technique, which overcomes this limitation, is presented with the consideration of the local magnetic saturation on the stator and rotor teeth. The results obtained with the nonlinear AM have been compared with the linear AM based on the subdomain method (i.e., without the saturation effect) and nonlinear finite-element method solutions. [ABSTRACT FROM AUTHOR]

In order to simplify the manufacturing process of variable reluctance (VR) resolvers for hybrid electric vehicle/electric vehicle (HEV/EV) applications, a novel VR resolver with nonoverlapping tooth–coil windings is proposed in this paper. A comparison of the winding configurations is first carried out between the existing and the proposed designs, followed by the description of the operating principle. Furthermore, the influence of actual application conditions is investigated by finite-element (FE) analyses, including operating speed and assembling eccentricity. In addition, identical stator and windings of the novel design can be employed in three resolvers of different rotor saliencies. The voltage difference among the three rotor combinations, as well as the detecting accuracy, is further investigated. Finally, prototypes are fabricated and tested to verify the analyses. [ABSTRACT FROM PUBLISHER]

This paper presents the analysis of a brushless doubly fed reluctance machine (BDFRM) for renewable energy applications with an emphasis on the rotor design. The BDFRM stator includes two sets of windings, i.e., the control winding (CW) and power winding (PW). The PW is connected to the grid, while the CW links the grid by a power converter of fractional rating to regulate the operating speed. This reduces the converter cost, and the brushless configuration enhances the reliability. In this paper, the reluctance rotor of the BDFRM, which is similar to that of a synchronous reluctance machine, is designed and analyzed in order to improve the performance. The influence of the total MMF and its allocation to the two stator windings are also discussed in relation to the machine performance. Finite-element analysis is used for performance simulation. The experimental study validates the proposed design for a small BDFRM. [ABSTRACT FROM PUBLISHER]

This paper presents an optimal design of the rotor pole in a novel axial-flux brushless doubly fed reluctance machine (AF-BDFRM), which features higher torque and power density than its counterpart radial-flux BDFRM. The rotor span and rotor overhang lengths were the optimized parameters, with the goals of improving torque density and improving the quality of the output power, i.e., reducing the torque ripple. The optimal design process was applied to obtain the optimized shape for maximizing torque density while minimizing torque ripple in a 16 kW machine. Then, the optimal design results were verified by means of the transient 3-D finite-element analysis. Furthermore, the results of the optimally designed rotor pole were compared with those of a previously developed diamond shape. Finally, a sample prototype of one HP was selected for testing, considering the manufacturing cost and available testing facilities to verify the proper working of the novel AF-BDFRM. [ABSTRACT FROM PUBLISHER]

The relationship between the well-known competitive torque density and less-competitive power factor of reluctance synchronous machines (RSMs) is investigated in this study. The investigation was carried out by implementing a complete machine model in the optimization, with varying machine-pole number and flux-barrier number combinations. Furthermore, the study consists of a multiobjective design optimization implementing a weighted-factor optimization technique. Determination of the weighting of this specific parameter relationship enables the designer to select an optimum multiobjective relationship during optimization. A specific machine was selected for analysis, then analyzed and manufactured for validation of simulation results. [ABSTRACT FROM AUTHOR]

This paper presents a novel 6/5 segmental rotor-type switched reluctance motor (SRM) for cooling fan application. Unlike conventional structures, the rotor of the proposed structure is constructed from a series of discrete segments, and the stator is constructed from two types of stator poles: exciting and auxiliary poles. Meanwhile, the windings are only placed around the exciting poles, resulting in short flux paths and no flux reversal in the stator of the proposed SRM. Hence, the proposed structure may increase the electrical utilization and reduce magnetomotive force (MMF) requirement compared to conventional SRMs. To verify the proposed structure, the operation principle and the design rules of the proposed structure are illustrated and expounded. The finite-element method (FEM) is employed to get the static and dynamic characteristics of the conventional 12/8 and proposed SRMs. Furthermore, the prototype is manufactured and tested. Finally, the simulation and experimental results are presented and analyzed to verify the effectiveness of the proposed SRM. [ABSTRACT FROM AUTHOR]

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

This paper examines the effect of frame on the acoustic noise and vibration of a high-speed and high-power switched reluctance machine (SRM). Five types of frame/ribs are investigated, where different frame thicknesses, types of cooling ribs, and frame shapes have been analyzed. For this purpose, a 12/8 SRM has been designed at 22 000 r/min and 150 kW and two stages have been applied. In the first stage, a new equivalent stiffness of the frame is utilized in order to estimate the resonant frequencies for different frame shapes. The paper provides a mathematical calculation method and evaluates its effectiveness with finite-element simulations. The results indicate an improvement between 4% and 25% in the estimation natural frequencies. The second stage includes the vibration and acoustic noise analysis using 3-D finite-element method. Considerations for acoustic noise reduction in high-speed SRM using different frame types and cooling ribs are discussed. Particularly, radial and screw-type configurations represent a better solution to decrease the sound pressure level up to 12 dB. [ABSTRACT FROM PUBLISHER]

The double-stator switched reluctance motor (DSSRM) has a potential to produce more power per volume than other types of SRMs. This paper offers a new design strategy concentrating on power rating to calculate the dimensions of a DSSRM. The new strategy is based on dissecting the DSSRM into two inner and outer rotor SRMs. In this regard, both inner and outer rotor SRMs are designed separately, and then, the results are merged together. The characteristics of the DSSRM are achieved utilizing analytical design and 3-D finite-element analysis (FEA). In addition, the obtained results are compared with dual SRM. To determine the appropriate performance of the motor, the magnetic analysis is performed utilizing a 3-D model. In addition, to achieve optimal operation, two different winding configurations are investigated and compared with each other. Finally, a prototype of the flat-type cup-shape DSSRM with a segmented rotor is fabricated and tested in the laboratory. The results of the analytical calculations and the FEA are validated by a testing motor, which show the accuracy and the design strategy, and it can be extensible to other types of motors. [ABSTRACT FROM PUBLISHER]

This paper develops an approach that is capable of accurately predicting the performance of synchronous reluctance motors (SynRMs). The SynRMs receive increasing attention and have been used in many industrial applications. The 2-D finite element analysis (FEA) is usually considered to be competent for design and analysis of SynRMs. However, the power factor of SynRMs is likely to be considerably overestimated. This would then lead to an underestimation of current required and cause problems for the design of electronic drivers. Compensation should be made to improve the accuracy of the analysis for SynRMs although there does not seem to be a solution put forward so far. The research in this paper shows that the exclusion of end turn leakage inductances in 2-D analysis is a key factor to cause such a significant difference. To resolve this problem, this paper analytically calculates the end turn leakage inductance, which is then incorporated into the 2-D FEA. The developed method is found to agree well with the experimental results, and it significantly improves the design accuracy and efficiency using only the 2-D FEA. [ABSTRACT FROM AUTHOR]