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A typical flywheel energy storage system (FESS) includes an electrical machine, a flywheel, and magnetic bearings, which are independent of each other. Therefore, the structure of FESS is complicated, which leads to the problems of high cost and low integration. This article presents a novel stator PM excitation solid rotor machine (SPE-SRM) for FESS, which integrates an electrical machine, flywheels, and a magnetic bearing. The design method of the SPE-SRM is presented specifically. First, the structure and operation principle of the SPE-SRM are illustrated. Second, the design and optimization of the flywheel-rotor are presented with considering of power, energy storage, and mechanical strength. Third, the magnetic equivalent circuit of the SPE-SRM is established to simplify the design. Besides, the armature reaction and leakage flux factor are investigated. Fourth, the performance indexes, including torque, suspension force, no-load back electromotive force (back-EMF), losses, and temperature rise are fully analyzed by the finite element analysis. Finally, a 22 kW prototype is manufactured and tested. The rationality of the concept and design is validated by experiments. The SPE-SRM has the merits of high integration, robust structure, and low cost, so it has the potential for wide application in FESS. [ABSTRACT FROM AUTHOR]

The trend in the industrial power electronics electrical drives is to reach high power density and high efficiency in variable load conditions at cost-effective unwasteful designs. Currently, motors with permanent magnets (such as IPMSM and PMaSynRM) are of great interest because of compactness, low losses, and high-torque capability. The performance of a drive system can be predicted with a motor electromagnetic authentic nonlinear model. In this article, a novel, fast, and precise motor model of PMaSynRM based on virtual reluctance (VR) is proposed. It takes into account the cross saturation, winding distribution, space harmonics, slotting effect, and stepped skewing. The VRs are identified by finite element analysis (FEA) and implemented in the time-stepping simulation. The flux inversion is not required. The proposed concept is useful in the rotating field or phase quantities (for open phase simulation). The model is also discretized for SiL and HiL applications. Finally, the validation in FEA and experimental setup was performed. [ABSTRACT FROM AUTHOR]

This article proposes a new “switched lumped reluctance network”-based equivalent circuit for a switched reluctance motor (SRM) under saturation. The proposed circuit incorporates the effects of the position-dependent switching of the phase windings and changing position of the rotor with respect to the stator. This feature enables the analysis of non-uniform and dynamic variation of flux in motor iron sections along with that in the air gap and their effects on the phase current. The proposed model, thus, emulates the operation of an SRM, more truly, through an equivalent circuit approach. The accuracy of the proposed model is verified by comparing the analytical results of five different stator–rotor sets (having different air gaps and tooth angular widths) with the finite-element method (FEM) simulated results and found to be in excellent mutual agreement. The static and dynamic performance obtained using the proposed model has been validated by experiments on a four-phase, 1-kW, 300-V, 1000-rpm SRM. [ABSTRACT FROM AUTHOR]

A novel electromagnetic force estimation using strain gauges attached to a laminated iron core method is proposed. Based on the strain gauge output, the electromagnetic force that occurs on the air-gap surface of the core is estimated with compensations for magnetostriction and nonuniform strain distribution. The proposed method is validated by comparing the electromagnetic force calculated in the finite element analysis and an experiment on a pair of C-shaped laminated iron cores. This article focuses on the force estimation in a pair of simple C-shaped cores, which are aimed at being a part of the stator and rotor of a switched reluctance machine. In future research, this basic approach will be extended to the estimation of the radial forces in switched reluctance motors to reduce the vibration and acoustic noise. [ABSTRACT FROM AUTHOR]

Vehicle to vehicle (V2V) energy sharing is emerging as an alternate solution to range anxiety and limited charging infrastructure challenges associated with electric vehicles (EVs). The existing off-board dc fast charging options for V2V application found in the literature are not effective due to the additional weight, size and cost of the external charger or interface. In this article, a new V2V interface is proposed in which both EV’s motor winding neutrals and negative rails of on-board drivetrains are directly connected to each other. This further helps in forming an integrated dual bidirectional dc–dc converter to control the direction of power flow. The proposed approach does not require reconfiguration of motor winding or mechanical clutch to arrest the motor from rotating and/or the reconfiguration of drivetrain inverter connections. The major hardware requirement for the proposed approach is, access to the already existing neutral connection of the EV motor phase windings. To achieve dc fast charging, all three-legs of voltage source inverter of energy Provider-EV are switched using interleaved pulsewidth modulation. Furthermore, finite element analysis is presented for 150 kW EV motor model and its performance validation with the high frequency dc current flowing in the motor windings during the V2V operation. A scaled lab prototype is developed to demonstrate the energy sharing between two Lithium-ion battery banks through the proposed direct V2V power transfer concept. [ABSTRACT FROM AUTHOR]

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]

In this article, we propose an interactive visualization method for motor design. We have proposed a visualization system for education using augmented reality (AR) and virtual reality (VR). As a further development of this, we are working on motor design as an industrial application. There are two issues in achieving high-speed interactivity. One is a fast mesh modification method in finite element analysis, and the other is a fast solving method. We propose a high-speed mesh modification method that utilizes regularly arranged grid points and coordinate transformation. In the proposed design system, the user can immediately observe the analysis result of the design change. Furthermore, if the proposed system is executed in cooperation with the projector, designers can change the design of the motor with their fingers and discuss it on the board. Furthermore, since this system can be executed on a Web browser, it can also be executed on a smartphone or tablet PC. [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]

The circumferential and axial widths of permanent magnet (PM) pole and E-shape stator pole of linear rotary motor with interlaced PM poles are very influential to the back electromotive force (EMF) and the flux leakage analysis is complex, which causes difficulty in optimization of the motor structure. One of the key issues in optimization design is to calculate the flux leakage accurately. In this article, the main flux and side flux variation laws of stator pole are derived by analytical method. The flux leakage can be divided into the flux leakage between the PM and the mover, flux leakage on the stator tooth tip, and the flux leakage between the adjacent PM poles and stator pole. The 3-D flux leakage calculation model is built, which is suitable for the calculation of magnetic flux based on different motor operating principles. Then the rotational and rectilinear back EMFs are calculated by analytical method, which are consistent with the results analyzed by 3-D finite element method. [ABSTRACT FROM AUTHOR]

This article proposes a model for obtaining the failure path current and torque waveforms in synchronous machines with saliency under interturn short circuits (ISC). The variations of the magnetomotive force (MMF) due to an ISC can lead to changes in the inductances, which lead to errors when modeling motors with ISC. A compact approach based on complex numbers is proposed to solve the dynamic ISC equation. The proposed method uses rotor reference frame variables and parameters as inputs. These rotor reference frame quantities are transformed to a stationary frame aligned with the faulted coil, thus extracting the real part of these quantities, allowing to solve the ISC dynamic equation quickly. Look-up tables are implemented to account for the MMF variations due to an ISC and saturation. The proposed model is validated with finite element analysis and experiments. [ABSTRACT FROM AUTHOR]

The permanent magnet linear motor (PMLM) has a variety of outstanding topological structures, such as flux switch structure and transverse flux structure. However, the inherited cogging force of PMLM is difficult to reduce without thrust damage. To solve the above-mentioned problem, this article investigates the thrust force, based on a novel flux-switching transverse-flux PMLM (FSTFPMLM) with a simple structure systematically, and provides the guidance to design the FSTFPMLM to achieve a larger thrust, with smaller cogging force. First, the basic structure and working principle of the FSTFPMLM are introduced. Second, an equivalent permeance model of the FSTFPMLM is proposed to calculate the thrust force, including cogging force, permanent magnet thrust, and winding reluctance force. Then, the leading parameters’ influence on the thrust force is investigated; it is concluded that the method effectively minimizes the cogging force and increases the thrust force. Finally, the prototype is manufactured, experiments are performed, and the experimental results agree well with the finite-element method results. This article verifies the effectiveness and practicability of the motor and the proposed analysis method, pointing out the motor's outstanding advantages in reducing cogging force while maintaining high thrust force. [ABSTRACT FROM AUTHOR]

At high gear ratios, surface permanent magnet (SPM) cycloidal magnetic gears (CyMGs) can achieve higher torque densities than SPM coaxial magnetic gears (CoMGs). This article introduces the radial flux reluctance CyMG (Rel CyMG) topology and its operating principles. The Rel CyMG replaces the permanent magnets (PMs) on an SPM CyMG’s inner rotor with salient teeth. Additionally, the Rel CyMG only requires half of the SPM CyMG’s outer rotor PM count to achieve the same gear ratio, which simplifies assembly and allows the use of wider magnets. This may improve high gear ratio designs’ manufacturability. A genetic algorithm (GA) was used with 2-D finite element analysis (FEA) to optimize Rel CyMGs, SPM CyMGs, and SPM CoMGs and demonstrate that SPM CyMGs significantly outperform the other topologies at higher gear ratios in terms of specific torque (ST) and PM ST. However, Rel CyMGs outperform SPM CoMGs at higher gear ratios, with respect to ST and PM ST. Rel CyMGs also eliminate the need for a PM retention sleeve and potentially enable the use of smaller air gaps, which can allow them to achieve slightly higher PM STs than SPM CyMGs at ultrahigh gear ratios. Employing Halbach arrays significantly improves both CyMG topologies’ ST. [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]

Stator and rotor cores of interior permanent magnet (IPM) motors are usually saturated, and the saturation distribution and saturation depth vary with the stator current. Also, their rotor structures are complex; hence, the saturation cannot be accurately reflected by a saturation factor. These considerations lead to the existing equivalent air-gap length models of induction motors and inset permanent magnet (PM) motors no longer suitable for IPM motors. Therefore, based on the consideration of stator and rotor saturation, this article proposes the equivalent air-gap length model of IPM motors expressed by magnetic potentials on the stator inner surface and the rotor outer surface. The proposed equivalent air-gap length model can accurately reflect the influences of complex structure and severe saturation of IPM motors. Compared with the existing models, the proposed one is no longer uniquely determined by motor structure parameters; it is also a function of stator current and rotor position. Furthermore, the obtained equivalent air-gap length model is combined with the winding function and the modified winding function to solve the inductances under different stator currents and different rotor eccentricity states. Finally, the proposed method is verified by both finite element analysis (FEA) and experiments. [ABSTRACT FROM AUTHOR]

According to International Electrotechnical Commission (IEC) 60034-1, in industrial applications not only efficiency but also power factors are important performance indexes. When comparing line motor to induction motor (IM), a line-start synchronous reluctance motor (LS-SynRM) has a high efficiency but a low power factor than that of IM. In this article, the analysis and design of LS-SynRM are carried out considering the rotor slot opening and bridges for improving the efficiency and power factor. The reference machine is selected with a 2.2 kW IM, and the performance of the reference model is analyzed based on finite element analysis (FEA). To analyze the effect of rotor slot opening and bridges, an optimal model of LS-SynRM is designed through a two-step design process. First, the design of rotor slot for synchronization is carried out, and second, the design of barriers using the response surface method (RSM) is carried out under the same conditions of the stator size of IM. Based on the basic model, the performances of LS-SynRM are analyzed according to the slot opening and bridges. Furthermore, the parametric analysis is carried out and the final model is designed considering the efficiency and power factor based on the design parameters. Finally, the final model is manufactured, and the experiment is carried out to verify the FEA result. [ABSTRACT FROM AUTHOR]

This work investigates the effect of design parameters of permanent magnets (PMs) and flux barriers (FBs) in the rotor on the anti-demagnetization ability (ADA) of fractional slot concentrated windings interior PM (IPM) motors for electric scooters. A 2.5 kW IPM motor (12 slots and 8 poles) is designed for a wide speed range, and its ADA associated with different PM and FB arrangements is studied under high temperature and high current density operations. The analysis shows the relationship between the ADA and characteristic current ($I_{\mathrm {ch}}$ , defined as the ratio of PM flux linkage to $d$ -axis inductance). It is also found that proper designs of FBs can significantly improve the ADA of the IPM motor without much affecting $I_{\mathrm {ch}}$. Thus, the motor ADA and performance can be simultaneously improved. Finite element analysis is used for evaluation, and experiments are conducted to validate the analysis. [ABSTRACT FROM AUTHOR]

In this article, a new asymmetric PM-placed rotor topology is applied to the conventional less-rare-Earth hybrid magnet machine, where such new placement of hybrid magnets can be designed to improve the torque performance effectively. Considering the difference between the two magnetic materials, the optimal placement scheme of NdFeB-PMs and ferrite-PMs in the rotor are determined by theoretical derivation of equivalent magnetic circuit and finite element analysis. Based on the torque component separation analysis using frozen permeability method, the sizes of the two magnets are preliminarily designed to improve the utilization of reluctance torque and to reduce the superposition coupling loss of PM torque. Then, based on the parameter sensitivity analysis, the proposed asymmetric-hybrid-PM machine (AHPM) is further optimized aiming at the multi-objective of torque performance and anti-demagnetization performance. Finally, a prototype motor is fabricated and tested. Both the theoretical analysis and experimental results verify the effectiveness and reasonability of the AHPM and the proposed design method. [ABSTRACT FROM AUTHOR]

This article employs grain-oriented (GO) silicon steel in an axial-flux permanent magnet (AFPM) machine to improve its torque and efficiency. Rolling direction of the GO material have been studied to ensure the machine’s main magnetic flux passes through the easy magnetization direction. Based on the study of the electromagnetic characteristics of AFPM machine, GO silicon steel is laminated to form a stator according to a certain lamination direction. The torque and efficiency of the proposed machine with GO material shows an increase in comparison with that of the conventional non-oriented (NO) silicon steel machine under identical conditions. In addition, an equivalent magnetic circuit model is established to illustrate little difference of electromagnetic property under no-load condition for the yokeless stator AFPM using two kinds of silicon steel sheet. Furthermore, a AFPM machine with stator yoke is also established to highlight the superiority of GO in the application of the AFPM machine with yokeless stator. [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]

Synchronous reluctance motors show nonlinear behavior in the high torque region due to core saturation, especially on the $d$ -axis. In this study, the maximum torque per ampere (MTPA) solution is sought in the mathematical frame. First, flux linkage data are obtained from finite element method, and fitted as the plane functions of currents by the least square method. Thereafter, the inductances are derived as binomials in $i_d$ and $i_q$. These analytic expressions of inductances are used in deriving a necessary condition for the MTPA, and constructing an on-line MTPA control method. The effectiveness is verified through simulation and experimental results. [ABSTRACT FROM AUTHOR]

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

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]

Switched reluctance motors (SRMs) have attracted much attention in industry due to the advantages of low cost, robust structure, high fault tolerance and high torque density. However, several disadvantages like high torque ripples and coil temperatures hinder their industrialization for some applications requiring high dynamic performance, like electric vehicles (EVs). In this paper, a multiobjective and multiphysics design optimization method considering both thermal and electromagnetic performance is presented for a 12/10 SRM. First, the topology of the SRM is introduced and the optimal parameters are defined. Then, the electromagnetic finite element model (FEM) is introduced and the 3D transient lumped-parameter thermal model (TLPTM), considering both axial and radial heat transfer for the SRM, is proposed. Second, the objectives and constraints of the optimization are determined. To improve the optimization efficiency, the sequential subspace optimization strategy is employed to find the optimal solution of this high-dimensional design optimization problem. Finally, to validate the effectiveness of the proposed method, both simulation and experimental results are given and discussed. Compared with the initial design, the optimal solution exhibits lower temperature, higher torque, lower torque ripple and less loss. [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]

An 8-pole 48-slot dual three-phase synchronous reluctance motor has been tested under half control mode, that is, when only a single three-phase system is supplied while the other is not operating. Changing the terminal connections of the motor prototype available, two different winding configurations have been tested. This allows their performances to be experimentally compared. At first, the cross coupling effect between the axis in $dq$ reference is analyzed, by measuring the flux linkages for different current combinations. The torque characteristics are compared in terms of torque map, maximum torque capability and torque ripple. Then the finite element analysis has been used to explain the experimental results and to investigate the radial forces on the rotor. Finally, the impact of a lack of symmetry between the two three-phase system is investigated. [ABSTRACT FROM AUTHOR]

A new method to detect the initial rotor position of switched reluctance machine (SRM) is presented in this article. Unlike most conventional position estimation methods, the proposed method does not need any extra premeasurement and only the data with finite element method (FEM) are required. First, a linear regression model (LRM) is presented to describe the relationship between FEM and measured inductance characteristics. Then, to detect the position, the residual sum of squares of the proposed LRM is considered as an objective function, which is a convex function with rotor position. The rotor position can be estimated by minimizing the objective function with the golden-section search method. Finally, the accuracy of the proposed estimation algorithm is validated by the experimental results on a three-phase 12/8 pole SRM prototype. Compared with the existing position estimation methods, the proposed method has higher accuracy and less measurement effort. The proposed method can serve as a supplement to provide accurate initial position information for incremental position sensors. [ABSTRACT FROM AUTHOR]

Energy storage is an emerging technology that can enable the transition toward renewable-energy-based distributed generation, reducing peak power demand and the time difference between production and use. The energy storage could be implemented both at grid level (concentrated) or at user level (distributed). Chemical batteries represent the de facto standard of storage systems for performance and maturity; however, batteries feature a quite large environmental footprint and use precious raw materials. Mechanical storage technologies could represent a viable alternative to chemical batteries, because of their reduced impacts on the environment and on raw materials. This article presents the design of a motor/generator for a flywheel energy storage at household level. Three reference machines were compared by means of finite element analysis: a traditional iron-core surface permanent-magnet (SPM) synchronous machine, a synchronous reluctance machine (SynchRel), and an ironless SPM synchronous machine. Simulation shows that the ironless machine is good candidate for distributed energy storage, because of its high efficiency, high discharge duration, and low losses. A prototype ironless machine was designed and manufactured. Experiments confirm the simulation results. [ABSTRACT FROM AUTHOR]

This paper presents a new structure of Permanent Magnet Flux-Switching Linear Motor (PM-FSLM) with a simple low weight modular primary and acceptable thrust ripple production. A flexible Magnetic Equivalent Circuit (MEC) is applied for modeling the proposed machine, which is capable to analyze the performance of different structures of PM-FSLMs. The saturation and end-effect phenomena are considered by a nonlinear permeability function and virtual zones at both ends of the machine, respectively. The machine operation under dynamic load is also investigated and its specifications are obtained. The proposed PM-FSLM has more power capability, lower current un-symmetry, and simpler mover structure compared to other ones, which can be mentioned as its benefits. Finally, the results of the proposed method are validated by the Finite Element Method (FEM) to show the effectiveness of the proposed MEC technique in terms of accuracy and processing time. The introduced linear machine and the proposed analysis method with adjustable accuracy are the paper novelties, which are presented in this work for the first time. [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]

Mutually coupled switched reluctance motors (MCSRMs) are alternatives in the family of reluctance machines that can overcome switched reluctance motor's (SRM's) system-level integration and control challenges by utilizing standard three-phase voltage source inverters. In this article, a novel segmented-rotor, fractional-slot, tooth-wound MCSRM with notched rotor design is presented, which has very low torque ripple compared to other machine types in the SRM family. The torque ripple is reduced to 3.6% without utilizing any current profiling techniques or torque sharing functions. The ripple minimization is achieved primarily through rotor segment shaping, which has a strong influence on stator flux densities, flux linkages, and torque harmonics. The design strategy, along with the optimization details, is presented for a 120 W, 12 slot-8 pole MCSRM. The designed MCSRM is prototyped for experimental verification and validation of the finite element analysis results and design methodology. [ABSTRACT FROM AUTHOR]

High-speed machines exhibit the advantages of super-high-power density, high efficiency, etc. and have been gaining more research attention in recent years. This article proposes an elaborate high-speed vernier reluctance machine (HSVRM) topology. The main advantages are as follows: (1) the stator adopts the so-called half-quasi-squirrel cage winding so that one side of all conductors is short connected and the other side is powered by modular inverter, (2) dc-biased current is fed into each conductor independently so that the machine can operate with the principle of magnetic field modulation, and (3) ladder rotor is equipped to weaken the torque ripple of the machine. Obviously, the machine topology significantly resolves the shortage of overlong end length and improves the fault-tolerant ability. In this article, the basic principle and electromagnetic characteristics of the machine will be analyzed by finite element analysis (FEA). [ABSTRACT FROM AUTHOR]

Compared with traditional linear motors, such as Linear Permanent Magnet Motors (LPMs) and Linear Induction Motors (LIMs), Linear Flux-Switching Permanent Magnet (LFSPM) motors have the merits of high efficiency, power density, with simple and robotic secondary structure. Despite these advantages, the flux-weakening ability of LFSPM motor is limited and thus the speed range of it is not ideal. As a promising choice, it is feasible to replace the PMs of LFSPM motors with coils made with High Temperature Superconducting (HTS) tapes. By using HTS material, High Temperature Superconducting Linear Flux-Switching Motors (HTS-LFSMs) have good flux-weakening ability while inheriting the edges of LFSM motors. Since the existence of HTS coils, the cooling system has a minimum size and has to take up certain room of the motor. When it comes to applications where the volume of motor is strictly restrained, there may not be enough room for a basic pattern of typical pole pitch combinations for HTS-LFSM, such as 12-7 or 12-9, leading to large thrust ripple. To solve this problem, a method of reducing thrust force using asymmetry mover structure is proposed based on a 9-5 pole pitch ratio. The mechanism and working principle are analyzed and the validation is verified with the help of Finite Element Method (FEM). [ABSTRACT FROM AUTHOR]

Both Linear Switched Reluctance Motor (LSRM) and Linear Flux-Switching Motor (LFSM) have the merits of none-adhesive thrust force and simple and robust secondary structures. Therefore, LSRM and LFSM are quite suitable for applications such as vertical lifting, wave power generation and urban railway transit. To further improve the power density of them, the field windings of LFSM and DC windings of LSRM can be replaced with High Temperature Superconducting (HTS) coils, and thus forming High Temperature Superconducting Linear Flux-Switching Motor (HTS-LFSM) and High Temperature Superconducting Linear Switched Reluctance Motor (HTS-LSRM). Despite their similar structure, they have different working principles and electromagnetic performances. To reveal their merits and drawbacks for urban railway transit system, a comparative investigation is conducted in this paper using Finite Element Method (FEM). [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]

In this paper, a novel topology for the flywheel battery is proposed, based on the axial split phase (ASP) bearingless switched reluctance machine (BSRM) concept. The topology and operating principle of the ASP-BSRM are explained, the electromagnetic characteristics, torque, suspension force and coupling performance are analyzed by 3-D finite element analysis (FEA). In order to improve the torque and suspension force of the ASP-BSRM, the single variable method by FEA is adopt to screen out the sensitive structure parameters, and a new multi-objective optimization design mothed based on random forest regression (RFR) and differential evolution (DE) is proposed to optimize the key parameters. The 3-D FEA of the complete system is performed, and simulation results verify the proposed topology overcomes the dead zone of suspension force and realize the decoupling between torque and suspension forces. Besides, the optimized torque and suspension force are improved by 4.15% and 12.91%, respectively. An experimental prototype is built to provide an experimental basis for investigation of the actual operating characteristics. The experimental results of the system are evaluated under different operating conditions and compared with FEA results. [ABSTRACT FROM AUTHOR]

Embedded applications like electric and hybrid vehicles are increasingly using electrical machines with a very high power/mass ratio. In this context, the design of such machines, very often operating at high speeds, becomes essential. However, in order to remain economically attractive, these machines cannot use rare earth magnets but at best include (low cost) ferrites. In this context, a significant number of publications have shown that synchronous reluctance machine (SynRM) may be a good choice. However, this type of machine gives poor performances due to the difficulty to get high saliency ratio. This saliency ratio may be improved by the use of low-cost ferrites that saturate the rotor magnetic bridges. The determination of the height of the magnetic bridges becomes then a problem of the prime importance to ensure both high-speed integrity and high saliency ratio. This article proposes a fast model based on the “Beam Theory Method (BTM),” which is intended to be integrated in an electromechanical optimization process. This method will be compared to another one that has been previously introduced for this type of problem: the equivalent ring method. The maximum mechanical stress at critical regions of the rotor of the assisted SynRM can then be calculated for different rotating speeds and rotor iron bridge thicknesses. By adopting the concept of stress concentration, both methods are compared with the results of finite element analyses. Finally, a prototype of the assisted SynRM is used to validate these results from finite element simulations. [ABSTRACT FROM AUTHOR]

This article proposes a concept for homothetic scaling of Synchronous Reluctance (SynRel) machines with the aim to generate a design for a wide range of power ratings. A generalized modeling approach, based on the saliency ratio, is presented in detail to analytically evaluate the magnetic behavior of the scaled SynRel machines. The analytical model has been applied to a wide range of machines and validated through finite element analysis. General scaling functions are derived to size and evaluate the performance of the scaled machines using the data resulting from the analytical model. The accuracy of the proposed functions is validated, for a range of operating conditions, comparing the results with the experimental measurement carried out on two 4-poles SynRel prototypes. These have been designed using the homothetic method proposed, which has been proven to be a quick and accurate preliminary sizing tool for SynRel motors. [ABSTRACT FROM AUTHOR]

In this article, a rotor magnetic potential (RMP) model is proposed, which can accurately describe the rotor surface magnetic potential distribution under the interaction of multi-excitation sources. Furthermore, a new magnetic equivalent circuit (MEC) model is used to model the complex saturation in the bridge region, which employs an improved nonlinear reluctance modeling method. Then, the unknown parameters in the RMP model are obtained by solving the MEC model. In this article, the RMP model and MEC model are combined to consider the stator and rotor saturation effects, and the magnetic field is calculated accurately. Compared with the existing RMP model, the proposed one can take into account the effects of the stator saturation and PM magnetic field. Compared with the existing MEC and equivalent magnetic network (EMN), the area of the nonlinear reluctance in this paper varies with excitation conditions, which can accurately consider the saturation effects in the bridge region. This improvement can improve calculation accuracy on the basis of reducing the number of nonlinear reluctances. Moreover, the proposed method does not need to consider the change of the air-gap reluctances caused by rotor rotation. Finally, the proposed method is verified by both finite element analysis and experiments. [ABSTRACT FROM AUTHOR]

This article aims to implement a fan motor design with an airfoil-shaped rotor via the newly developed 3-D printing method. This integrated design is originated from a flux-switching permanent magnet motor, in which the motor rotor can directly produce airflow without any external impellers. Such a design and manufacturing process can effectively enhance the robustness of the fan motor structure and increase its power density. This article adopts 3-D finite element analysis for electromagnetic and fluid field simulation. Moreover, a new metal 3-D printing method with a low core loss feature during high frequency operation is applied. Finally, the experimental results with a prototype are presented to verify the designed performance. [ABSTRACT FROM AUTHOR]

This article presents a method for the computation of the incremental inductances in a 12/10 variable flux reluctance machine (VFRM) using the hybrid analytical modeling coupled with a fixed-point nonlinear solver. The variation of incremental and apparent inductance with respect to the dc-field excitation is investigated for both zero and non-zero ac-field excitations. The results show that the difference between both inductance values is not negligible after 25 A/mm2 dc-current density for the investigated benchmark without the ac field. Moreover, when a non-zero ac field is introduced in addition to the dc-field, the apparent inductance becomes misleading not only under magnetic saturation but also under low excitation in the linear region of the saturation curve. The results obtained with the proposed nonlinear hybrid model are compared with the finite element method in terms of magnetic flux density distribution and incremental inductance value. The root-mean-square discrepancy of magnetic flux density distribution is found to be 37.6 mT. Furthermore, the discrepancy between incremental inductance results of the proposed method and the finite element model is calculated as 1.43%, while the proposed approach requires less post-processing and necessitates ten times less number of degrees-of-freedom. [ABSTRACT FROM AUTHOR]

Outer-rotor switched reluctance machines (SRMs) have drawn much attention as promising candidates for in-wheel direct-drive motors of future electric vehicles. This article presents a systematic performance comparison of three outer-rotor SRM topologies for in-wheel traction applications in terms of the specific torque, electromagnetic efficiency, torque ripple, radial force, and mechanical aspects. A generalized design optimization framework for SRMs is proposed to enable the fast evaluation of large numbers of designs generated from the differential evolution by incorporating an analytical current profile estimation into the transient finite element analysis. The relationship between the saliency ratio and converter volt-ampere rating is also discussed. The calculations are then benchmarked with the experimental results from an existing prototype. The effectiveness of the performance prediction method and the proposed optimization approach is validated. [ABSTRACT FROM AUTHOR]