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Fractional‐slot concentrated‐windings are appreciated for their simple construction, short end‐winding length, high copper fill factor, low cogging torque, good field‐weakening capability and fault‐tolerant ability. However, in comparison to the conventional distributed windings, the fractional‐slot concentrated‐windings are characterised with high space magnetomotive force (MMF) harmonics, which results in undesirable effects on the machine performance, such as localised core saturation, eddy current loss in the rotor and noise and vibration. In order to improve winding characteristics, several techniques have been developed recently. This manuscript introduces the 5 new winding topologies by using the general concept of stator slot shifting. It means that, in order to cancel undesirable MMF harmonics, by doubling (or tripling or even multiplying) the slot number and dividing the winding and then relatively shifting the winding by one (or more) slots, the undesirable harmonics have been eliminated effectively. The best choice is chosen according to the lowest amount of the MMF harmonic, highest value of winding factor and torque desirable characteristics. At the end, comprehensive comparisons for the designed synchronous reluctance motor (SynRel) equipped with proposed windings and also distributed winding are presented. The analytical study and 2D FEM analysis results show that it is possible to get an ideal low space‐harmonic winding topology, and consequently, a low torque ripple for these motors. [ABSTRACT FROM AUTHOR]

Summary: Predictive control of stator currents is a model‐based technique needing an estimation of rotor currents, which are normally not measured. These currents affect the evolution of the stator currents and, therefore, also affect the predictions used by the controller. The usual procedure consists in correcting their effect by a simple feedback technique. In this article, the estimation of rotor currents is tackled based in the induction machine equivalent circuit. The proposed estimation procedure aims at improving the predictions with respect to the usual procedure. Simulation and experimental results are provided for the particularly demanding case of a multi‐phase induction machine, showing the superiority of the proposal. [ABSTRACT FROM AUTHOR]

This paper investigates the accuracy of rotor‐locked transient‐response (RLTR)‐based vibration model for switched reluctance machines (SRM). RLTR is stator vibration stimulated by abrupt change of radial force when turning off one phase of SRM with rotor being locked, the total vibration of SRM can be modelled as linear superposition of RLTR series. An electromechanical model is built to clarify the generation of SRM vibration, it is revealed that some velocity‐depend terms in electromechanical model would be neglected when rotor is locked, it leads to inevitable difference of RLRT between rotor‐locked condition and rotational condition, the difference is illustrated through multi‐physics simulation. A harmonic radial force model is proposed to quantitatively evaluate the accuracy of RLTR‐based vibration model, radial force spectrums with locked rotor and rotational rotor are compared to predict relative error between RLTR‐based vibration and actual vibration. The influence of turn‐off angle and velocity on accuracy of RLTR‐based vibration model is also analysed. The accuracy of RLTR‐based vibration model is evaluated through experiment on 3‐phase 12/8 SRM, the results showed that: (1) the accuracy of RLTR‐based vibration model is impacted by turn‐off angle and velocity; (2) relative error between RLTR‐based vibration and actual vibration can be predicted using harmonic radial force model. This paper illustrates the generation mechanism of modelling error for commonly used RLTR‐based vibration model of SRM, the proposed error prediction method could lead to improved accuracy on SRM vibration model through error compensation. [ABSTRACT FROM AUTHOR]

A linear switched reluctance motor (LSRM) is designed for electric propulsion application in a Magnetically Levitated (Maglev) train with the base speed of 7.6 m/s and operating at a maximum of 27.8 m/s. In such high‐speed LSRMs, windage loss is one of the key issues of concern. Usually, windage loss accounts for approximately 0.5% below the base speed, 20% above the base speed, and 45% at higher speeds of the total loss of the LSRM. One of the many parameters affecting this windage loss is the stator slot profile. This research work studies about different stator slot structures, thereby aiming to reduce the windage loss through computational fluid dynamics analysis. Furthermore, experimental testing of the LSRM is also done to verify the simulation results. [ABSTRACT FROM AUTHOR]

This paper proposes an automatic design method of typical parameters such as number of phases, number of poles, stack thickness, stator outer diameter, rotor outer diameter, and number of turns of a switched reluctance motor from the requirement of the N‐T characteristic. In particular, a specific parameter related to the magnetic saturation is defined in order to arbitrarily determine how much to use the magnetic properties of the iron core material. In the proposed method, the typical motor parameters in order to realize a miniaturized volume which satisfies an input N‐T characteristic are obtained by setting the parameter related to magnetic saturation, maximum electrical frequency, maximum current density, maximum copper loss, conductor slot fill factor, magnetic properties of material, and input voltage. The designed motor is analyzed using the Finite Element Method (FEM) in order to validate the proposed method. [ABSTRACT FROM AUTHOR]

Here a new sensitive fault detection criterion is proposed, based on the stationary wavelet transform (SWT) decomposition components of the stator currents, for the online detection of stator winding turn‐to‐turn faults at an early stage of development. The energies of the desired detail components are calculated and the normalized Euclidean distance of the energy differences between the three phases is used as a new fault detection criterion. The robustness of the proposed technique against the presence of rotor turn‐to‐turn faults and loading variations is demonstrated. In addition, an adaptive threshold level as a function of the voltage unbalance factor is proposed to guarantee the robustness of the diagnostic technique against unbalanced voltage sources. Experimental results demonstrate the effectiveness and sensitivity of the proposed diagnostic approach for the detection of stator faults in line‐connected and inverter‐fed motors. [ABSTRACT FROM AUTHOR]

This study proposes a state formulation of the space‐vector dynamic model of the Synchronous Reluctance Motor (SynRM) considering both saturation and cross‐saturation effects. The proposed model adopts the stator currents as state variables and has been theoretically developed in both the rotor and stator reference frames. The proposed magnetic model is based on a flux versus current approach and relies on the knowledge of 11 parameters. Starting from the definition of a suitable co‐energy variation function, new flux versus current functions have been initially developed, based on the hyperbolic functions and, consequently, the static and dynamic inductance versus current functions have been deduced. The dynamic inductance functions have been derived so to fulfill the reciprocity conditions. This study presents also a technique for the estimation of the parameters of the proposed magnetic model, which is based on stand‐still tests without the need to lock the rotor. The identification process has been performed based on the minimization of a suitably defined error function including the difference between the measured and estimated stator fluxes. The proposed parameter estimation technique has been tested in both numerical simulation and experimentally on a suitably developed test set‐up, permitting the experimental validation of the proposed model. [ABSTRACT FROM AUTHOR]

The magnetic effects and consequently the radial force are the main causes of noise in switched reluctance motors (SRMs). In this study a new design for SRM is developed in order to reduce acoustic noise. In this research a new design for SRM is developed in order to reduce the acoustic noise. In this investigation, at first, different SRM structures are simulated using JMAG software. An 8/6‐pole SRM is designed and built with special modification in the rotor and stator structures. For increasing mechanical strength, trapezoidal stator and rotor pole shape with poles arc βr = βs = 21° are proposed. In this design the taper angles of stator and rotor poles are equal. For noise reduction, the mechanical restructuring is done according to stress analysis. The new designed SRM are simulated and tested experimentally under no‐load and full‐load conditions. The results are shown and compared. Comparison between these results and the results of other structures shows that the acoustic noise of the newly designed motor is reduced considerably. The results show an acoustic noise reduction of ∼72% in new structure SRM. [ABSTRACT FROM AUTHOR]

The rotor structure of synchronous reluctance motor (SynRm) is usually provided with redial ribs to improve structural ruggedness for high‐speed operation. While these radial ribs contribute to mechanical robustness, they also reduce the average torque and limit the flux‐weakening capability due to an increase in inductance along the q ‐axis. To address this issue, the rotor design is refined by adopting non‐magnetic radial ribs in this study. The introduction of titanium as non‐magnetic material for radial ribs prevents magnetic leakage flux from flowing along the q ‐axis, and thereby improves the average torque, saliency ratio, efficiency and power factor of the SynRm. Furthermore, along with the electromagnetic analysis, the mechanical integrity of the proposed rotor design is also investigated. Two prototypes rated 1 kW at 1500 rpm are fabricated using both the conventional and the proposed rotor design, while the stator and other parameters are maintained constant in the two cases. The conventional design uses magnetic radial ribs whereas the proposed design uses non‐magnetic radial ribs. Finally, a thorough comparative study, including inductance tests on the prototypes, is performed between the proposed and the conventional SynRm, confirming the strengths of the technology solution being set forth. [ABSTRACT FROM AUTHOR]

A comprehensive study on divided‐teeth permanent‐magnet assisted outer‐rotor switched reluctance motors (SRMs) is carried out. Foremost, it looks into the impact of the number of teeth per stator pole. The average and maximum torque profiles of the compared structures are obtained using finite‐element simulations. It is shown that as the number of teeth increases, higher torque is obtained. Then, six small PMs are inserted inside the teeth of neighbouring modules to form new hybrid reluctance motors (HRMs). The four permanent‐magnet assisted SRMs are compared in terms of the average and maximum torques using finite‐element simulations. Based on the comparison results, the 48/50 HRM is selected as the best candidate among all compared SRMs and HRMs. The magnetic flux density distributions, static torque, and flux linkage characteristics of the proposed HRM are obtained. Moreover, the cogging torque profile of the motor is obtained, which approximates to zero. Next, the steady‐state performances of the proposed HRM are obtained under low‐ and high‐operating speeds. Finally, a prototype of the machine is constructed and the test results are obtained and compared with those of the simulations, which show that there is a good agreement between these results. [ABSTRACT FROM AUTHOR]

The multi‐layer switched reluctance motor (SRM) is a special type of the SRM which can be utilised appropriately in high‐power applications such as electric vehicle (EV). Thermal modelling of the multi‐layer SRM is considered for the first time in the present study and a lumped parameter thermal model is introduced for quick prediction of temperature rise in this motor. In the introduced lumped thermal model, independent thermal networks are considered for different parts of the machine including frame, stator yoke, stator pole, winding, air‐gap, end‐winding, end‐cap air, rotor pole, rotor core and shaft. All details of the modelling and the required equations are given and therefore someone can use the model easily. The developed thermal model is applied to a typical two‐layer 8/6 SRM and a prototyped three‐layer 8/8 SRM and the simulation results are then compared with those derived from three‐dimensional finite element (FE) method using ANSYS FE package and experimental results. These comparisons show well high computation speed and accuracy of the lumped thermal model developed for the multi‐layer SRM. [ABSTRACT FROM AUTHOR]

Flux saturation of switched reluctance motors (SRMs) and severe non‐linear relationship between current, position angles and electromagnetic torque lead to the difficulty of torque modelling and analysis. Specifically, the permeability of ferromagnetic material varies with the magnetic field strength H, and the core saturation effect increases with H. In this study, piecewise curve fitting method is adopted for analysing the relationship between the permeability and the stator winding current. The magnetic equivalent circuit method is adopted to build an analytical model for a SRM where the saturation of ferromagnetic material is expressed in the form of variable permeance. The comparison between computation results of analytical model and finite‐element method simulation results verifies the correctness of the proposed model. Simulation and experimental research of a SRM speed control system verify the practicability of the model. [ABSTRACT FROM AUTHOR]

This study proposes a modified structure of the E‐core permanent magnet (PM) assist switched reluctance motor by relocating the PM blades inside the stator core. For this purpose, the PMs are removed from the stator poles and placed slantwise inside the yoke. The proposed yoke‐PM assist structure is characterised with higher average torque and a lower torque ripple with respect to the conventional pole‐PM assist structure. An analytical approach based on the magnetic equivalent circuit is applied at the preliminary design stage to predict the performance of the motor. Based on the presented analytical modelling, the physical dimensions of the motor are optimised via a genetic algorithm to maximise the motor torque and the overall steady state performance. For further verifications, the finite‐element analysis simulation results are verified by the experimental tests on the motor prototype. [ABSTRACT FROM AUTHOR]

In this paper, a concentrated‐wound exterior‐rotor direct‐drive electric bicycle (e‐bike) mutually coupled switched reluctance motor (MCSRM) has been designed to match the performance parameters and dimensional constraints of a commercially available permanent magnet e‐bike motor. Different stator and rotor pole configurations are compared for a 3‐phase MCSRM. During the design process, many parameters have been evaluated and analysed. The finalised performance capabilities of all pole configurations are summarised, and the choice of pole configuration for the final design is justified. The full dynamic torque‐speed performance of the finalised 15/10 MCSRM is presented, along with a detailed thermal analysis. Finally, the MCSRM performance is compared to a 12/16 non‐coupled SRM and a commercially available permanent magnet motor. [ABSTRACT FROM AUTHOR]

The long stator of linear synchronous reluctance motor (LSynRM) consists only of low‐cost permeable material. Hence, LSynRM has a good application prospect in long‐distance drive systems. What about the electromagnetic performance of LSynRM under the constraints of installation size of rail transit? What are the advantages of LSynRM compared with the existing linear induction motor (LIM)? Research is non‐existent in academic circles. The purpose of this study is to compare LSynRM with LIM used in rail transit and give a comprehensive evaluation. First, a LIM used in Guangzhou Metro was analysed. Second, the working principle of LSynRM was analysed, and the selection principles of key parameters were determined. On this basis, the relevant parameters were optimized by using two‐dimensional finite‐element analysis (FEA) software. Then, the output characteristics of LIM and LSynRM were compared. The influence of ferrite on LSynRM was explored in view of the low power factor. The influence of winding end effect is explored through three‐dimensional FEA. The thrust force and power factor of LSynRM are corrected and the model is adjusted. Finally, the system cost and energy consumption of the two motors based on Guangzhou Metro Line 4 were estimated and compared in detail. [ABSTRACT FROM AUTHOR]

Since the traditional direct torque control (DTC) of switched reluctance motors (SRMs) has the shortcomings of large torque ripple and non‐constant switching frequency, this study proposes the deadbeat‐direct torque and flux‐linkage control (DB‐DTFC) method for SRM. By analysing the basic principles of SRM, a discrete‐time model is established to predict the future states of the SRM drive system. With DB‐DTFC, the stator flux and torque can be manipulated during each pulse‐width modulation cycle to minimise torque ripple during operation. As a result, the proposed DB‐DTFC can minimise the torque ripple as well as apply space‐vector modulation with a constant switching frequency. Finally, to verify its effectiveness, DB‐DTFC was applied to the 15 kW three‐phase 12/8‐pole SRM test bench in real time and the results are compared with conventional DTC. [ABSTRACT FROM AUTHOR]

This study presents an investigation on iron loss and start-up ability of a 1.5 kW output power with rated speed 5850 r/min 6/2 switched reluctance machine (SRM), which is used as a prime motor to directly drive centrifugal blower. Two winding connection types of the SRM are investigated, including the symmetrical magnetic topology (SyMT) and asymmetrical magnetic topology (ASyMT). The two types are proposed to settle poor self-start ability of the 6/2 SRM and high iron loss density of highspeed SRM. According to the simulation results, the SyMT has merit of self-start ability, i.e. no risk of start-up failure, whereas the ASyMT has advantage of low iron loss, i.e. low iron loss density on stator and rotor. Prototypes are manufactured to confirm and verify the predicted results and the test results prove the correctness of the analyses. [ABSTRACT FROM AUTHOR]

Finding an optimally designed synchronous reluctance machine with desired performance among all possible combinations of the stator and rotor with different shapes of barriers requires long execution time, which is an overwhelming task. Selecting the number of flux barriers, for instance, in accordance with the pre‐designed stator has a significant effect on the torque ripple. To tackle these issues, this study presents a comprehensive design procedure of an external rotor synchronous reluctance machine suitable for an electric bike application that includes considerations such as electro‐magnetic and mechanical aspects. Dimensions of the internal stator with tapered slots are calculated. Additionally, a global parameter, insulation ratio in the q‐axis, is used to link the microscopic parameters. Seeking for the optimal design through the insulation ratio effectively reduced the number of geometric parameters involved in the rotor shape optimisation. The preliminary rotor design is used to run multi‐objective optimisation to provide further improvement to the average torque and torque ripple. Utilising the finite‐element method, thermal and structural analyses are conducted to guarantee the safe operation of the designed motor under a steady‐state condition. Finally, measurement results of a 250 W‐fabricated motor are compared with the predicted results, which validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In this study, an initial rotor position estimation at standstill condition is presented for reliable operation of switched reluctance motor (SRM) without initialising machine parameters for light electric vehicle (LEV) applications. The prime objective of this method is to startup an SRM without using the mechanical position sensor, and eliminate the starting hesitation and starting jerk issues from standstill condition. In the proposed method, the initial rotor position at standstill is determined by injecting a single pulse dc voltage simultaneously into all stator phase windings for a very short period (microsecond). The obtained current envelope data is then used to calculate the initial rotor position with the quadratic polynomial interpolation technique without any prior knowledge of other motor parameters. The experimental results for a 3.5 kW, 6/4 SRM are provided to substantiate the overall good performance. The developed system can be considered as a strong candidate for high precision LEV applications. [ABSTRACT FROM AUTHOR]

In order to improve the operation performance and decrease the torque ripple of switched reluctance motor (SRM), a new current control method for SRM based on voltage space vector was proposed. In which the stator windings are excited by sinusoidal current with a DC offset to realise the unipolar current excitation. In this control system, zero vectors were used to control zero‐sequence current alone and non‐zero voltage space vector was selected to control d–q‐axis current considering coupling. The reluctance torque component was offset by injecting third harmonic current into the DC bias current, and copper loss was minimised by selecting appropriate current ratio. Experiences verified that the new method can effectively control SRM current. The torque ripple can be reduced with third times harmonic current injection, but the efficiency is also decreased[AQ ID=Q1]. Compared with the traditional control method, the proposed method is simple, easy to implement, and can effectively suppress torque ripple. [ABSTRACT FROM AUTHOR]

The main objective of this study is the analytical modelling of two short‐flux‐path two‐phase reluctance motors with E‐type stators: first, a switched reluctance motor and second, a hybrid‐excitation reluctance motor (HRM). The former has no permanent magnets in its structure, whilst in the latter, there are magnets inside the common poles. Firstly, finite element analysis (FEA) is adopted to obtain the flux paths distribution in the proposed structures. Then, a precise magnetic circuit model (MCM), which considers all leakages and fringing effects, is built and the permeances of the machine are calculated for any rotor position based on the predicted flux flow patterns. Torque and inductance curves and steady‐state current and voltage waveforms are also carried out. Finally, both motor prototypes are fabricated and the experimental results are obtained and compared with those of MCM and FEA. This comparative study confirms the validity and accuracy of the developed MCMs. In addition, the torque profiles of the proposed structures and two other conventional and C‐type reluctance motors are compared. It is shown that the proposed HRM has superior characteristics amongst all compared structures. [ABSTRACT FROM AUTHOR]

This study presents the evaluation of performance indexes of a novel synchronous reluctance motor (NSynRM) that has an axially sinusoidal rotor lamination shape. The stator of a 5.5 kW, 4‐pole, 50 Hz conventional three‐phase squirrel cage induction motor, with distributed and chorded by one slot, double‐layer winding, is used for both standard and NSynRMs. Owing to the nature of the sinusoidal rotor structure, the three‐dimensional finite element analysis (FEA) is utilised to study the electromagnetic parameters of interests. The NSynRM with sinusoidal rotor shape results is compared with the standard SynRM without cut‐off on the q‐axis. The FEA results are validated by means of practical measurements. [ABSTRACT FROM AUTHOR]

Summary: This paper addresses the problem of on‐line parameter estimation of switched reluctance motors and provides, to the best of the authors' knowledge, the first result that takes into account the dynamics of both electrical and mechanical subsystems. Based on a widely‐used standard model of the motor and establishing a reasonable structure for modeling the unknown load torque, a linear parametric model is derived and a 2‐stage identification scheme is proposed and implemented with the recursive least‐squares algorithm with forgetting factor. It is assumed that stator voltages and currents and rotor position and speed are available through measurements. Numerical simulations and experimental tests are included for a 3‐phase 12/8 switched reluctance motor. The results show a good performance of the proposed methodology, and the estimated parameters are validated through their use in a closed‐loop control scheme. Key features of the proposed solution are that it does not rely on locked‐rotor tests nor does it assume previous knowledge of the magnetization curves of the motor. The estimation scheme is intended to improve the performance and efficiency of currently available control algorithms, and it is potentially useful for the design of selfcommissioning switched reluctance drives, ie, drives that can automatically adjust the controller parameters for a wide range of motors and loads. [ABSTRACT FROM AUTHOR]

The double-stator configuration of the switched reluctance machine (SRM) aims to maximise the energy conversion efficiency by optimising the ratio of motional force to the total magnetic force. Maintaining the attractive features of SRM, the double-stator switched reluctance machine (DSSRM) proves to have higher torque/power density than the conventional SRM, which is a crucial feature for traction applications. The original winding configuration used in DSSRM is the full-pitch winding, which yields high-power density but causes significant heat within the machine's end windings. As end windings do not take part in torque generation, concentrated windings were proposed to reduce the heat as well as to reduce the size, cost, and weight of the machine. This study provides a detailed comparative analysis of the effects that the winding configuration has on the performance of a 100 kW DSSRM, with emphasis on flux density distribution, efficiency, and heat generation. It is concluded that the concentrated windings are a better alternative to the full-pitch windings in DSSRM. [ABSTRACT FROM AUTHOR]

In this Letter, three types of bearingless switched reluctance machines (BSRMs) with different hybrid stator structures are designed and analysed. First of all, topologies of three BSRMs, the conventional 8/10 pole, 12/14 pole BSRMs and a novel 12/12 pole BSRM with axial split phase inner stator permanent magnet structure, are given. Then, the electromagnetic performances, including the distribution of magnetic fields, suspension force and electromagnetic torque are comprehensively compared by means of 2D and 3D finite‐element method (FEM). The results based on theoretical analysis and FEM reveal that the proposed 12/12 pole BSRM would exhibit complete decoupling, shorter magnetic circuit, higher torque (power) density and suspension force than the conventional ones. Further, it is found that four degree‐of‐freedom suspension of the rotor can be realised by two‐phase suspension windings in the proposed 12/12 pole BSRM. Finally, a prototype machine is designed and manufactured to verify the validity of the topology design and electromagnetic performance. [ABSTRACT FROM AUTHOR]

A hybrid double stator bearingless switched reluctance motor with advantages of high suspension output, small loss and weak coupling is presented. This motor can realise electric/power generation and radial two‐degree‐of‐freedom suspension. The biased magnetic field for producing radial force is provided by a permanent magnet, which reduces system power consumption. Self‐decoupling is realised between a torque system and suspension system according to the mechanical structure design. Furthermore, the radial force is approximately constant when the suspension current is constant, thereby improving the controllability of the system. The operation principle is introduced and the electromagnetic characteristics are analysed through the time‐stepping finite element method. This analysis verifies the effectiveness of the theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper presents a multi‐physic analytical model for a permanent magnet assisted synchronous reluctance motor. The proposed model consists of: an electromagnetic model, an electrical model, a loss model, and a thermal model. The electromagnetic model is based on Maxwell's equations. Stator and rotor magnetic saturation is considered, as well as the effect of the magnetic bridges of the flux‐barriers. The electrical model computes the terminal voltage and power factor. Copper loss and iron losses are also considered. The thermal model makes an estimation of the winding and magnet temperature. The goal is to compute the motor performances (average torque, voltage, power factor, efficiency etc.) for several current values and current angles. The analytical model results are compared with those from a finite element model and are subsequently validated by an experimental prototype. [ABSTRACT FROM AUTHOR]

SUMMARY The motor efficiencies of switched reluctance motors (SRMs) are inferior to those of permanent magnet synchronous motors. This paper describes a design procedure for an SRM to obtain a higher motor efficiency. The first step in the design procedure makes clear the principle for improving the motor efficiency. The cross-sectional and axial shapes of the rotor and stator cores are designed by magnetic field analysis with the two-dimensional (2D) and 3D finite element method. A high-efficiency SRM with 12 stator poles and eight rotor poles is designed. The designed SRM was produced experimentally, and was tested to verify its performance. The motor efficiency was improved in comparison to the standard SRM with six stator poles and four rotor poles. [ABSTRACT FROM AUTHOR]

SUMMARY This paper proposes vector control specialized for a switched reluctance motor (SRM) drive. Because it is a unipolar drive, a sinusoidal current with a dc offset is applied to each circuit instead of the conventional trapezoidal current. The current consists of dc and ac components which can be identified by their generation of a (virtual) rotor flux and rotating stator magnetic field, respectively. Thus, the vector control system can be developed in the same way as conventional ac machines. The proposed technique provides new mathematical models of SRMs on a rotating reference frame and achieves precise and fast torque response and advanced operations such as linear torque-current control and maximum-torque-per-ampere control. The vector control theory was verified through simulations and experiments. [ABSTRACT FROM AUTHOR]

This study presents a design methodology based on scale models for low speed switched reluctance generators (SRG). This study is motivated by the application of SRG to direct-drive wind turbines and other low speed renewable energy systems. In direct drive energy converters considerable simplifications result from the elimination of the gear box which has generally been used to interface a slowly rotating shaft with the generator shaft. The comparison and evaluation of magnetic structures plays an important role in the SRG design. General design methodologies are usually oriented towards the evaluation of stator/rotor poles combinations for regular switched reluctance machines. Besides covering that feature, the formulation of scale laws proposed is also suitable to compare other SRG topologies distinguished by different characteristics of electric and magnetic circuits and their own relative position. In addition, this methodology can be extended to other physical phenomena such as thermal changes and magnetic saturation by introducing some constraints. The running example compares a modular short flux-path topology versus a low speed 20 kW prototype SRG designed for a direct drive wind turbine. The modular topology can optimise the efficiency and weight taking benefits from the significant gain of power per unit of volume and lower losses. [ABSTRACT FROM AUTHOR]

In this paper, a new type 12/14 bearingless switched reluctance motor with double windings is presented. The stator includes two types of poles such as suspending pole and torque pole. Different from the previous 8/10 structure, double windings including bias winding and control winding are installed on the same suspending pole. In addition, in order to reduce the coupling between torque and levitation force, the stator torque poles are shifted with one angle. Windings of two adjacent torque poles are connected in series. Therefore in order to explain advantages of proposed motor, structure and basic operating principle are introduced. In the meanwhile, levitation force is derived by means of equivalent magnetic circuit. The force characteristics with respect to current and displacement are analysed. In addition, by means of finite element analysis, coupling characteristic and self‐starting characteristic are investigated. The validity of the structure is verified by the analysis and experimental results. [ABSTRACT FROM AUTHOR]

This study presents a novel switched reluctance machine (SRM) with modular E‐core stators and multi‐layer common rotors for high reliability applications. The stator is composed of six independent modular E‐cores with the windings wound around the yoke of the E‐cores. The rotor consists of three magnetically independent common rotors which are place in the same shaft without any angular shift. The equivalent magnetic circuit (EMC) models of this new SRM at the aligned and unaligned positions are described. To evaluate the motor performance, two types of analysis, namely, approximate simplified two‐dimensional (2D) model and 3D model finite‐element analysis (FEA) have been utilised. The 2D FEA static and dynamic results are compared with 3D FEA results. Furthermore, comparisons between the novel modular SRM and a conventional 6/4 SRM are made. Finally, a prototype of this modular SRM has been fabricated and tested in the laboratory. Comparison between FEA and EMC analysis for flux linkage are made and compared with measured characteristics. The simulated and measured phase currents and average torque are also presented and compared to verify the analytical and simulation results. [ABSTRACT FROM AUTHOR]

A hybrid double stator bearingless switched reluctance motor with advantages of high suspension output, small loss and weak coupling is presented. This motor can realise electric/power generation and radial two-degree-of-freedom suspension. The biased magnetic field for producing radial force is provided by a permanent magnet, which reduces system power consumption. Self-decoupling is realised between a torque system and suspension system according to the mechanical structure design. Furthermore, the radial force is approximately constant when the suspension current is constant, thereby improving the controllability of the system. The operation principle is introduced and the electromagnetic characteristics are analysed through the timestepping finite element method. This analysis verifies the effectiveness of the theoretical analysis. [ABSTRACT FROM AUTHOR]

The article focuses on single winding bearingless switched reluctance motors and its potential use for energy storage. It describes switched reluctance motors, noting the change of the motor design from outer stator and inner rotor to inner stator and outer rotor. It mentions the advantages of the developed flywheels as energy storage systems as well as recommends a suspension force modelling method based on the Maxwell tensor method.