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Variable reluctance motor is becoming a competitive candidate among all other machines available due to its added features. The development of variable reluctance motor is simple due to the simple construction of rotor without any permanent magnets. Reduced complexity in structure paves the way for low-cost motor and it also leads to the application of SRM in a wide manner. In order that the machine could be used in various applications, it is much necessary to have a suitable driving system (converter configuration). The best choice of converter for SRM would pave the way for desirable control of the machine. The proposed work includes the design and analyses of an appropriate driver configuration for SRM and interface it with the motor which is already designed and analyzed using ANSYS Maxwell. The design and analysis of the converter are carried out using the ANSYS Simplorer tool box. [ABSTRACT FROM AUTHOR]

—In this study, the design and analysis of multi-layer fully pitched winding switched reluctance motor (MFP-SRM) for general use (submersible pump, electric vehicles, etc.) have been performed. It is seen that the multi-layer switched reluctance motor (SRM) has higher output power when compared to the single-layer SRM. In multi-layer SRM, the motors in the layers are electromagnetically independent of each other although they are identically the same motors with the same characteristics in terms of performance and geometry. Each layer of the MFP-SRM which is designed in this study consists of a 6/4 pole fully pitched SRM (FP-SRM) and these motors are magnetically independent of each other. In the MFP-SRM, which is designed as a double layer, there is a 15° phase difference between the rotor position angles and torque profile curves of each layer. With the phase difference that changes depending on the number of layers, each layer contributes to the total torque production of the profile, ensuring a smooth profile. According to the results of the 3D FEM analysis, it is seen that the proposed multi-layer motor structure has high starting torque and low torque ripple properties. In the analysis carried out in the range of 3–15 Amperes, the torque ripple of the traditional FP-SRM varies between 31.99% and 38.19%, while the torque ripple of the proposed MFP-SRM only varies between 3.23% and 7.11%. [ABSTRACT FROM AUTHOR]

SRMs have high torque ripples. Modifying the stator and rotor shape of SRMs is one of their methods to remove torque ripples. In this study, new rotor and stator geometries have been proposed for SRM. Performance characteristics are obtained and dynamic analyses are carried out for both novel and classical 6/4 SRMs. FFT analyses of the torque characteristics are also performed for the both SRMs. The changes in performance and the FFT results of torque characteristics are determined for both the current-controlled and uncontrolled operations in both SRMs. 23.60% and 15.20% improvements in torque ripples are achieved for the uncontrolled and current-controlled operations in SRMs respectively. When the FFT analyses are applied to the torque characteristics, the THD values are obtained as 21.19% and 8.31% in the uncontrolled and controlled motor current operations respectively. A 122 W three-phase 6/4 SRM simulation based on the MATLAB–SIMULINK environment is performed to validate the improvement of the torque ripple of the proposed model. [ABSTRACT FROM AUTHOR]

In this paper, two different strategies are combined to optimize the phase current control for switched reluctance motor (SRM). Firstly, considering the sampling and computation delay, a current prediction chopping control method is proposed to alleviate the current ripple during the entire excitation phase chopping process. Secondly, in order to cut down the large current ripple in the initial stage of phase current establishment and the excessive output current of the battery, a partitioned current control method is proposed to control the phase current with different control logic at different rotor zones. Finally, the two control strategies are combined to further optimize the phase current. In order to verify the proposed combined control strategy, a three-phase 12/8 poles SRM simulation model and experimental platform are built. The simulations and experiments are carried out to verify the effectiveness of the proposed control strategy. [ABSTRACT FROM AUTHOR]

This paper describes a sensorless control technique Based on current waveform detection for Switched Reluctance Motor (SRM) over full speed-range. For conventional sensorless method, the resistive drop and the back- EMF are always neglected, which may cause some errors in position determination and restrict the rotor speed-range. To overcome this problem, an improved current-slope-difference based approach is presented for sensorless starting and continuous low-speed sensorless operation. For medium and higher speeds, a current-gradient method is used for sensorless operation. Based on the proposed sensorless method, the position sensorless operation within the whole speed range of the SRM can be easily implemented. Finally, the experimental results demonstrate the validity of the hybrid sensorless approach in the full speed region. [ABSTRACT FROM AUTHOR]

In this paper, a novel linear switched reluctance motor (LSRM) is introduced in which the total electromagnetic losses and dimensions are significantly reduced compared to the conventional LSRMs. The LSRM's stator has a segmental structure, while its rotor possesses a seven pole configuration with three rotor poles equipped with the winding sets to generate the magnetic flux. The other remaining four rotor poles, i.e., auxiliary poles, are responsible for closing the magnetic flux path loop. In the proposed LSRM-auxiliary mover poles (LSRM-AMP), the flux path length is effectively reduced using the optimized provided auxiliary poles. Therefore, the required magnetomotive force (MMF) is reduced compared to the conventional LSRMs. In addition, as only half of the generated flux passes the stator segments, the dimensions of the stator segments and their corresponding weights are significantly reduced without any saturation issue. In order to verify the finite element (FE)-based performance prediction of the proposed structure, the electromagnetic operating principles and the design rules of the LSRM-AMP are separately investigated. A sensitivity analysis and comparative study for the proposed LSRM-AMP and conventional LSRM topologies are presented to show the performance and characteristics superiority of the optimized LSRM-AMP structure. [ABSTRACT FROM AUTHOR]

Abstract—This article presents a novel torque ripple minimization approach based on the genetic algorithm (GA) for the switched reluctance motor (SRM) drives. The fitness function of the GA is designed on the basis of two main optimization criteria. The first optimization criteria; three objectives are defined to optimize commutation angles minimizing torque ripple and copper loss. The second optimization criteria; an objective is defined to eliminate the negative torque which decreases the average torque in SRM drives. The achievement of all objectives depends on the adjusting appropriate the commutation angles of the torque sharing functions (TSF) during the commutation period. All of conventional TSFs are dependent on three different commutation angles, namely turn-on, turn-off, and overlapping. Due to the nonlinear phase inductances of SRM, the delay of current rising and falling time are not unity in overlapping commutation region. To overcome the separation of the incoming and outgoing phase currents during the commutation region, rise angle, and fall angle are used instead of overlapping angle. GA is used to optimize the commutation angles of conventional (sinusoidal) TSF and improved (sinusoidal) TSF. At the same time, the elimination negative torque effects on torque ripple, average torque, and copper loss is investigated. [ABSTRACT FROM AUTHOR]

This paper proposes a straightforward second-order sliding mode control (SMC) approach to minimize current distortions and torque ripples of a switched reluctance motor (SRM). In the first step, conventional SMC is briefly recalled and detailed. Then, a special attention is paid to the synthesis and the implementation of a second-order (SM2) approach. Stability analysis of these two approaches is ensured. It will be shown that the proposed second-order SM approach offers a lower harmonic distortion of the motor currents, a reduction of the torque ripples, and the elimination of chattering phenomena. The effectiveness of the proposed SM2 is verified by simulation results then validated by experiments. [ABSTRACT FROM AUTHOR]

Aiming at the problem of severe unbalanced magnetic force (UMF) of the switched reluctance motors (SRMs) caused by eccentricity, this paper analyses the radial electromagnetic force's spatial distribution and frequencies under eccentricity and conduct a compensation method for the UMF. Firstly, the expression of the radial electromagnetic force under eccentricity is derived by using the method of magnetomotive force multiplying permeance, combining with the modification of the permeance. Secondly, the UMF is reduced by applying compensation current to the two stator poles of the permeance-descending phase. The selection of the stator poles and the calculation of the compensation current are decided according to the direction and the value of the unbalanced flux density. Dynamic eccentricity (DE) will produce new frequencies and spatial orders of the radial electromagnetic force, and the static eccentricity (SE) only produces the new spatial orders. The results obtained by the finite element model prove that this method can effectively reduce the UMF without sacrificing the output torque performance. [ABSTRACT FROM AUTHOR]

This paper presents four-quadrant sensorless control in switched reluctance machine (SRM) over the wide speed range. The proposed sensorless control technique could be employed not only at low speed with current chopping control (CCC) but also at high speed with angle position control (APC). At startup and low speed, the narrow voltage pulse is injected into the idle phases and the rotor position zone is determined by comparing the measured flux linkage with four flux linkage-current curves. The same flux linkage-current curves also can be adopted for rotor positions estimation at medium and high speeds. Two flux linkage-current characteristic curves in the inductance rising zone are employed to estimate the rotor position for motoring mode and the other two curves in the inductance falling zone are used to estimate the rotor position for braking mode. The experiments on a three-phase 12/8 pole SRM drive platform are carried out to verify the effectiveness of the proposed sensorless control technique. [ABSTRACT FROM AUTHOR]

This work investigates the application of the adjoint variable method (AVM) to switched reluctance motors (SRMs). A MATLAB toolbox developed by the authors estimates the sensitivities of the required objective function with respect to different geometric design parameters using at most one adjoint simulation. In this work, the AVM evaluates the sensitivities of the x and y components of the magnetic flux density, the phase flux linkage, and the electromagnetic torque of switched reluctance motors with respect to teeth height, yoke thickness, teeth pole arc angle, and teeth taper angle of both stator and rotor. The nonlinearity of the motor magnetic material is taken into consideration. The estimated sensitivities using AVM are compared with those obtained using the more accurate but time intensive central finite differences (CFD). An interior-point optimization algorithm utilizes the sensitivities of the electromagnetic torque of an SRM to maximize the motor static torque profile. Structural mapping technique is used to control the geometric design parameters through the optimization process. [ABSTRACT FROM AUTHOR]

Here we present a comprehensive analysis of structural performance of Induction Machine (IM) and Switched Reluctance Machine (SRM) rotors under different operational conditions. Electric machines are susceptible to forces of diverse origins. In addition to traditionally considered magnetic and centrifugal forces, this article discusses independent and inclusive effects of thermal expansion and shaft attachment techniques on structural integrity of the machines. A comparative analysis of structural performance of IMs and SRMs has also been performed, under a range of scenarios, to facilitate application-specific machine selection from a structural perspective. [ABSTRACT FROM AUTHOR]

In this work, we report on the application of the adjoint variable method (AVM) to sensitivity analysis of switched reluctance motors (SRMs). Using at most one adjoint simulation, the sensitivities of the desired response with respect to all geometrical and material parameters are estimated. In this work, the AVM evaluates the sensitivities of the air region magnetic energy and the electromagnetic torque of a SRM with respect to all parameters. Good match is achieved between the AVM sensitivities and those estimated using the more accurate but computationally expensive central finite differences (CFD). [ABSTRACT FROM AUTHOR]

The accurate prediction of temperature rise in various parts of a machine plays a significant role in ensuring that the machine delivers the required performance avoiding failures that arise due to high temperatures. In this paper, a lumped parameter thermal model is presented for exterior-rotor axial flux switched reluctance motors. Depending on its geometry, each part of the motor is modeled as a thermal equivalent circuit based on general cylindrical or cuboidal components. A total thermal network is obtained by proper connection of these sub-circuits. The model was calibrated by a stationary test; then, running conditions were applied to the model. The sensitivity of the model to the heat transfer coefficients was investigated by considering the effect of the coefficient variation on the estimated steady-state temperatures. Results show that the winding temperature, as the hottest part of the motor, is the most sensitive to the frame-to-ambient heat transfer coefficients. [ABSTRACT FROM AUTHOR]

Torque ripple is a major problem for switched reluctance motors, which may cause undesirable vibration and acoustic noise, especially at low speed. This paper presents an optimal topology structure of rotor for 8/6 pole switched reluctance motor by using the level set method. The nonlinear ferromagnetic material boundary of rotor pole is implicitly represented through an embedded level set function. This method is applied to obtaining the optimal distributions of material in the design domain for minimizing torque ripple and maximizing average torque. In the optimization objective function, the reluctivity of ferromagnetic material is selected as the design variable. The normal velocity is derived from sensitivity analysis, where the adjoint variable method is utilized. Two-dimensional finite element method is employed to calculate the electromagnetic parameters of this electric machine. Analysis results obtained from the transient simulation of electromagnetic field coupled with control circuit show that the torque ripple is reduced effectively by using the optimized rotor structure. [ABSTRACT FROM AUTHOR]

Double-rotor switched reluctance machine (DRSRM) integrates two switched reluctance machines (SRMs) into one housing, providing a compact solution for hybrid power trains so that one DRSRM can replace two electric machines. This paper presents a new DRSRM design in which the stator flux barriers are removed and the flux lines in the interior and exterior machines are more evenly distributed. The effects of stator flux barriers are investigated, the loss mechanism in the DRSRM is analyzed, and finally, various winding configurations are compared. It is concluded that flux lines are more evenly distributed in the stator, reducing iron saturation and losses, while the interior and exterior machines can be independently controlled without sacrificing performance. Moreover, winding polarity in DRSRM is critical to reduce stator iron saturation and thereby losses. [ABSTRACT FROM PUBLISHER]

The rotor radial force is changed by adjusting the windings current value to control rotor suspension for various kinds of bearingless switched reluctance motor (BSRM). To accomplish the BSRM's suspension control, the radial force analytical model is necessary. Currently the mathematic relationship among radial force, winding currents, and rotor rotation angle has been built for double-winding BSRM, but the rotor eccentricity displacement has not been considered. That is, the existing radial force analytical model only can be used to analyze rotor radial force when rotor shaft is located in the central position. Actually, the rotor radial force is significantly affected by the rotor shaft eccentricity displacement. It is difficult for the bearingless motor to keep the rotor shaft staying in the central position, and the rotor shaft always runs around the central position with an eccentricity displacement. The rotor eccentricity caused by the radial force is considered in the paper to obtain the air-gap permeance and the windings inductances. Furthermore, the radial forces analytical model considering the rotor eccentricity displacement is derived. Finally, the finite-element method (FEM)-based results are applied and the dynamics simulation using the proposed model is accomplished to verify the correctness of the model. [ABSTRACT FROM AUTHOR]

This article describes the control optimization of a slotted switched reluctance generator for low-speed applications. The machine is simulated with the finite-element method. The turn-off and turn-on angles are optimized by means of a genetic algorithm to maximize the output power and minimize the torque ripple. First, these two criteria are optimized separately with a mono-objective genetic algorithm, and then a multi-objective Pareto genetic algorithm is used. An analysis of optimized parameters and resulting current waveforms is also performed. Experimental results based on a 6/4 switched reluctance generator are also presented. [ABSTRACT FROM AUTHOR]

Abstract—Analytic modeling of radial forces is proposed for the novel bearingless switched reluctance motor, where the rotor eccentricity is taken into account. The novel bearingless switched reluctance motor's model is never disclosed, even though there are many advantages, such as fewer suspension windings and simpler control circuit and algorithm, when compared to the conventional bearingless switched reluctance motor. The analytic model of radial forces is very important to achieve this new bearingless switched reluctance motor's suspension control. The rotor eccentricity is a key cause to affect the radial forces. This article calculates the air-gap permeances through considering rotor eccentricity. The self-inductance and mutual-inductance expressions of the motor torque windings and the suspension windings are derived by using the magnetic equivalent circuit method. The derived radial force model discloses the effects of winding currents, rotor position angle, and rotor eccentricity displacement. The finite-element analysis based results verify the built model. [ABSTRACT FROM PUBLISHER]

A switching flux reference estimation based method for sensorless control of switched reluctance motors is proposed in this article. The basic idea of the method is to estimate switching-on and switching-off flux linkage references from the giving switching angles range and measured phase current. Real-time comparing the estimated flux linkage with estimated switching flux references, the driving signals can be obtained for sensorless control and rotor speed estimation. For closed-loop control, switching-off angle is fixed for speed estimation, and switching-on angle is regulated by the speed deviation proportional-integrator controller. The process to estimate the switching flux references is greatly simplified compared with conventional flux/current methods; it is easily implemented and is suitable for low-cost industry applications. To verify the proposed method, experiments were conducted on a 1-kW, 3-phase 12/8 switched reluctance motor. Experimental results show that speed variable performance of the sensorless drive is comparable with that of position sensors. [ABSTRACT FROM AUTHOR]

The knowledge of air velocity inside all the air regions in any electric machine is essential in performing various air velocity-dependent analyses such as calculation of windage loss, thermal analysis, determination of effectiveness of cooling, and estimation of life of insulators. This article, in this context, introduces computational fluid dynamics (CFD) procedure for the evaluation of air velocity distribution inside electric machines. One of the today's most experimented machine, the switched reluctance motor (SRM), is considered for the illustration. A two-dimensional finite element approach (FEA) for CFD is described and results are discussed. [ABSTRACT FROM AUTHOR]

Torque ripple control of switched reluctance motor has been the main issue in the application of this motor. Conventional proportional plus integration, proportional plus integration and differentiation, variable structure proportional plus integration, and recently, feed-back linearization control techniques with number of reference torques have been used for torque ripple minimization. In this paper an optimal commutation strategy witha novel reference torque is used in order to achieve a minimum torque ripple using different conventional and nonconventional control techniques. This novel reference torque with feedback linearization technique minimizes the torque ripple, peak of phase current, and controlling energy. As a result, the proposed approach provides a simple way to obtaining a switched reluctance motor with optimal performance. [ABSTRACT FROM AUTHOR]

In this paper, the authors present a nonlinear modeling of multiphase switched reluctance motors (SRMs) in which both the self- and mutual-couplings among all phases are described in terms of self-inductance, mutual-inductance and coupling coefficients. Moreover, a novel iteration algorithm to solve the initial value problems of the modeling is proposed. Expressions for computing the instantaneous torque from both the self- and mutual-coupling are derived, too. The simulation and experimental results are compared as a validation of the proposed methods and iteration algorithms. [ABSTRACT FROM AUTHOR]