Switched reluctance motor drives — recent advances

The objective of this paper is to review the state-of-the-art and recent developments in Switched Reluctance Motor (SRM) drives. The interest for improved performance and reliability has motivated many SRM advances in the recent years. Even after almost 30 years of research in SRM, which might appear to be the simplest of all machines, there remain critical issues to be explored to gain deeper insight into the SRM technology. The paper briefly discusses the historical background and the basic operating principles of the motor. The topics discussed include the current state of research in converter topologies, control algorithms, torque ripple, noise, and sensorless operation. Recent advances in the field of SRMs indicates that they will have an increasing influence in the area of variable speed drives in the coming decades.     

An improved method for the determination of saturationcharacteristics of switched reluctance motors

Experimental determination of magnetization characteristics of switched reluctance motors (SRMs) is quite important in their accurate performance prediction. Over the last decade, various experimental procedures have been used to obtain these characteristics. Every evolved new method has its own limitations and constraints. This paper describes an improved, simple and cost effective experimental procedure and an equally simple post-experimental data processing to obtain the flux-linkage-current curves at varying rotor positions of the SRM. The experimental results on a 4 kW, four-phase, 8/6 pole SRMs show the effectiveness of the method and the results compare well with the previously results compare well with the previously published results of similar and higher rating SRM's     

Simple model of switched-reluctance Machine based only on aligned and unaligned position data

We propose a simple equivalent circuit and mathematical model for the magnetic system of switched-reluctance machines (SRMs). The saturation effect in the stator yokes is taken into account, and phase inductance is represented as a function of phase current and reluctance in the air gap. We also propose a simple method for measurement and evaluation of the parameters of SRMs based on the model and present results of numerical simulations and real experiments on an SRM as an autonomous single-phase generator.     

OPTIMIZATION OF SOLID ROCKET MOTOR IGNITER PERFORMANCE REQUIREMENTS†

A numerical technique is presented for optimizing a set of solid rocket motor (SRM) ignition control variables to achieve a specific requirement or set of requirements to be used in preliminary design of an SRM igniter. The mathematical model of the igniter transients uses a simplified ignition simulation routine to calculate igniter and SRM performance. The object function to be optimized (minimized) is typically the summation of The absolute values of the differences between the desired and computed thrust values of the SRM at specified times during ignition. Constraints are imposed in the form of limiting values of igniter characteristics, flame-spreading speeds and/or maximum rate of pressure rise in the SRM. Optimization is obtained using a direct pattern search technique to determine the required values of the controlling variables. Examples are presented which illustrate the ability of the technique to meet practical design requirements. Computational results are shown to be consistent with the static test performance of Space Shuttle SRMs. In addition.it is shown that the method is capable of evaluating certain often unknown parameters, such as flame-spreading speed, from test data.     

A novel switched reluctance motor with C-core stators

This paper presents a novel switched reluctance motor (SRM) design in which the stator is simply formed from C-cores. Unlike conventional SRMs, the windings of the new motor can be individually wound into the stator cores without complex winding equipment. Because of the inherent axial field distribution, this type of SRM requires a three-dimensional (3-D) finite-element analysis (FEA) model for detailed flux analysis. This paper proposes an approximated two-dimensional FEA model to speed up computational time. In addition, since the proper current that ensures operation in the saturated region (to maximize torque and efficiency) is often hard to determine systemically, the paper proposes a simple method to determine the optimum operating current so that one can easily decide the rated current and also obtain the maximum motor efficiency. Finally, the paper compares some characteristics of a traditional SRM with those of the proposed SRM. The comparison shows that the proposed SRM performs well in terms of torque and efficiency, and provides a higher degree of flexibility in winding design.     

Analysis and characterization of switched reluctance motors: Part II. Flow, thermal, and vibration analyses

This paper presents new approaches for certain mechanical characterizations, such as thermal and vibration analyses, of switched reluctance motors (SRMs). The paper presents, in three parts, the modeling and simulation procedure for three-dimensional (3-D) finite-element analysis (FEA)-based flow analysis, flow-analysis-based thermal analysis, and a realistic vibration analysis. Section I documents a computational fluid dynamics (CFD) flow analysis procedure for the evaluation of the air velocity distribution inside the SRM at any speed. Section II presents a prediction method for steady-state and transient thermal characteristics of an SRM, using 3-D FEA. The convection coefficient at various heat-dissipating surfaces inside SRM, which is not a material property, but a quantity that solely depends on the air velocity at the respective surfaces, is the major parameter to be evaluated for an accurate simulation of heat distribution. The results of CFD analysis are used, for the first time on SRM, for this purpose. Windage loss calculation, one of the other applications of CFD, is introduced. Vibration in electric motors is an inevitable, at the same time undesirable, property that originates from four major sources: mechanical, magnetic, applied loads and, to a smaller extent, the associated electronic devices. Section III presents: 1) a thorough numerical study of vibration analysis in SRMs, using 3-D FEA methodology, covering all the above vibration sources except the electronics; 2) a 3-D modal analysis of SRMs including stator and rotor structures, shaft, end shields, bearings, and housing; 3) an unbalanced rotor dynamics analysis; 4) associated harmonic analysis; and 5) a stress analysis under various loading conditions. The 3-D vibration analyses presented in this paper to examine the vibration in SRM as a whole are new additions to SRM vibration analysis. Section IV concludes the paper. Future work in every section is highlighted.     

Experimental Investigations on Computer-Based Methods for Determination of Static Electromagnetic Characteristics of Switched Reluctance Motors

Because of the doubly salient structure of the switched reluctance motor (SRM) and its intentional operation in deep magnetic saturation for higher power density, its static electromagnetic characteristics are highly nonlinear functions of rotor position and phase current. This makes the accurate experimental measurement/determination of these characteristics a difficult task. This paper presents a comprehensive discussion and analysis on the different (most practiced) computer-based methods for the determination of these characteristics for a typical SRM. A digital signal processor (DSP)-based completely automated SRM drive system has been used for these studies. For all the offline computations, user-friendly MATLAB/Simulink-based models have been developed. The experimental methods, computational models, measurement results, and appropriate postmortem discussions for the determination of static flux linkage, inductance, and electromagnetic torque characteristics for an 8/6 four-phase SRM are reported.      

Analysis and characterization of switched reluctance motors: Part I /sub y/namic, static, and frequency spectrum analyses

This paper consists of three parts. Section I explores two software applications for modeling and simulating the dynamic characteristics of switched reluctance motors (SRMs). The software applications are the electromechanical structure system (EMSS), which is a tool within the proprietary Maxwell SPICE environment, and power system computer-aided design (PSCAD). The major parameter of an SRM, the nonlinear winding inductance, which determines the dynamic torque, is individually modeled for use with these applications. Simulation of the dynamic torque and the speed for any load is discussed. Section II presents a new stator geometry for SRMs that improves the torque profile. In the new geometry, pole shoes are affixed to the stator poles. The paper discusses a sensitivity study of the torque profile using a two-dimensional finite-element field simulation. Section III presents a frequency spectrum analysis of torque profile using the fast Fourier transform (FFT) capability of MATLAB. Salient features of this analysis for torque profile of SRM and the results of simulation are presented. Section IV concludes the paper.     

Determination of polycyclic aromatic hydrocarbons with molecular weight 300 and 302 in environmental-matrix standard reference materials by gas chromatography/mass spectrometry

An analytical approach based on gas chromatography/ mass spectrometry (GC/MS) is presented for the measurement of polycyclic aromatic hydrocarbons with molecular weight (MW) 300 and 302 in environmental samples. Three different GC stationary phases [5% and 50% phenyl methylpolysiloxane and dimethyl (50% liquid crystalline) polysiloxane] were compared, and retention indexes (RI) are given for 23 individual MW 302 isomers. Identification of MW 300 and 302 isomers in four environmental-matrix Standard Reference Materials (SRMs) (SRM 1597, coal tar extract; SRM 1648 and SRM 1649a, air particulate matter; and SRM 1941, marine sediment) was based on the comparison of RI data and mass spectra from authentic standards. Dibenzo[a,l]pyrene, which is of considerable interest because of its high carcinogenicity, was identified and quantified in the four environmental-matrix SRMs. A total of 23 isomers of MW 302 and four isomers of MW 300 were quantified in four different environmental-matrix SRMs, and the results are compared to previously reported results based on liquid chromatography with fluorescence detection.     

Temperature Rise Analysis of Switched Reluctance Motors Due to Electromagnetic Losses

We present a finite-element analysis of the temperature rise of switched reluctance motors (SRM) due to electromagnetic losses. We estimate the various components of electromagnetic losses, including core loss in the lamination as well as copper and eddy-current losses in windings, and then predict the temperature rise within the motor due to these losses. We present simulation results for an 8/6 SRM and discuss various aspects of thermal design of SRMs. To validate the procedure for the estimation of electromagnetic losses, we compare predicted and measured losses.      

System response matrix calculation using symmetries for dual‐head PET scanners

Positron emission tomography (PET) scanner with dual‐head geometry offers better spatial resolution and higher sensitivity for dedicated application when compared with conventional full‐ring PET scanners. However, this configuration suffers from limited‐angle projection and depth‐of‐interaction (DOI) effects. Accurate modeling of the system response matrix (SRM) and its incorporation into iterative methods can help to obtain images with better quality. In this paper, we proposed a line‐of‐response (LOR) based symmetry approach to calculate the SRM of PET scanners with dual‐head geometry. Both Monte Carlo (MC) and analytically computed SRMs were obtained and named MC SRM and geometrical SRM respectively, with their performances been compared using simulated phantom studies. The point source study shows that the resolution in directions parallel to the detector is rather uniform, with a full width at half maximum (FWHM) of 0.6～0.7 mm and 0.6～0.8 mm using MC and geometrical SRMs respectively. While the spatial resolution in the direction perpendicular to the detector is much worse, when moving towards the detector panel from the field‐of‐view (FOV) center, the FWHM changes from 1.5 mm to 1.8 mm and 2.4 mm to 3.1 mm using MC and geometrical SRMs, which is caused by the missing of projection views. Images generated using MC SRM also show better stochastic quality and quantitative performance. © 2013 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 23, 205–214, 2013     

Diagnosis of Static Eccentricity in Switched Reluctance Motors Based on Mutually Induced Voltages

This paper presents a novel method for diagnosis of eccentricity in a switched reluctance motor (SRM). The method employs two-dimensional finite-element analysis to calculate mutual fluxes and mutually induced voltages in an 8/6 SRM. An investigation of the effect of static eccentricity on these quantities shows that eccentricity has a considerable effect on them. Since flux measurement is costly, the method introduces mutual voltage as a suitable criterion for diagnosis of eccentricity in SRMs.      

Simultaneous mass bias and fractionation corrections utilizing isotopic solid standards and laser ablation ICPMS

Homogeneous incorporation of analytes of known isotopic abundance into sol-gel-derived standards that mimic important mineral systems has the potential to contribute significantly to providing solid standard benchmarks for a range of applications. This preliminary study reports on the synthesis of solid glass standards produced via the sol-gel method and their doping with Standard Reference Material (SRM) 981 Common Lead Isotopic Standard and SRM 982 Equal-Atom Lead Isotopic Standard. Custom isotopic materials were also prepared using mixtures of the two isotopic SRMs. Particles from these solid samples were then introduced into an inductively coupled plasma mass spectrometer via laser ablation to determine whether materials of suitable homogeneity could be developed as isotopic reference materials. Preliminary results for Pb isotope ratios show that these solid isotopic reference standards are capable of correcting for instrumental mass bias and laser ablation-induced bias due to fractionation simultaneously. Correction factors generated from the quotient of the certified and measured Pb isotopic ratios in sol-gel disks spiked with SRMs 981 and 982 were successfully applied to produce accurate isotope ratios using comparative control/unknown checks. These correction factors were also used to assign Pb isotopic ratios in NIST SRM 612 Trace Elements in Glass that were in excellent agreement with published measurements, suggesting that tunable matrix sol-gel disks can serve as adequate control matrixes for evaluation of isotope ratios in glass samples.     

Modeling switched-reluctance Machines by decomposition of double magnetic saliencies

This paper presents a novel analytical model for a switched-reluctance machine (SRM) based on decomposition of its inherent double joint magnetic saliencies due to rotor and stator salient poles and saturation of magnetic field at high stator currents. With this method, the magnetic characteristics of the motor, such as flux linkage and incremental inductance, are decomposed to vector functions of rotor position and phase current. Dynamic state and torque equations for the SRM are derived on the basis of this representation. The proposed model is appropriate for online identification and for sensorless position control algorithms. It is easy to implement and computationally efficient. Comparison of the predicted motor magnetic characteristics to machine data from finite-element analysis verifies the accuracy of the model.     

Improvement in the field-weakening performance of switched reluctance machine with continuous mode

A new operation mode for switched reluctance motors (SRMs), called 'continuous mode', is described. By using this mode, the torque and then power in field-weakening mode can be considerably increased without any hardware modifications. Consequently, power and torque densities of SRMs become comparable to other technologies (synchronous and induction motors) and with a field weakening operation over a large speed range. This new degree of freedom makes it possible to improve the motor design, by modifying the rotor pole arc size or the windings turns per pole. Only simulation results are presented here, for a 12/8 SRM. Results confirm that the maximum power is improved (constant power on a very large speed range) and with a higher efficiency than that in the classical discontinuous mode.     

Summarizing the effectiveness of supercritical fluid extraction of polycyclic aromatic hydrocarbons from natural matrix environmental samples

A summary of the supercritical fluid extraction (SFE) of polycyclic aromatic hydrocarbons (PAHs) from four natural matrix Standard Reference Materials (SRMs) is presented. The work involved the investigation of the effects of extraction fluid [carbon dioxide (CO(2)), chlorodifluoromethane (R22), and 1,1,1,2-tetrafluoroethane (HFC134a)], fluid modifier (dichloromethane and aniline), temperature (60, 150, and 200 °C) and added water on the SFE recoveries of PAHs compared to certified results from Soxhlet extractions. For SRM 1649a (Urban Dust/Organics), R22 yielded excellent recoveries (>90% of certified concentrations) of all PAHs measured, while results for the same SRM using HFC134a as the fluid were typically <80% of the certified concentrations for most of the PAHs measured. For SRM 1941a and 1944, both aquatic sediments with similar physical and chemical compositions, extractions of the wet materials with dichloromethane-modified CO(2) (10%, v/v) yielded quantitative recoveries of all PAHs for SRM 1944 but an obvious trend of lower recoveries for higher molecular weight PAHs (≥228 amu) for SRM 1941a. Results of SFEs of SRM 1650 (Diesel Particulate Matter) showed that this material is the most refractory of the SRMs investigated in this study, with recoveries of indeno[1,2,3-cd]pyrene and benzo[ghi]perylene at <20% of the Soxhlet results.     

Magnetic circuit model for the mutually coupled switched-reluctancemachine

The mutually coupled switched-reluctance motor (SRM) appears to have several performance advantages over other motor technologies. The existence of strong coupling between phases, however, makes the analysis of this machine quite complicated. Preliminary design of this machine can be greatly accelerated by the ability to evaluate potential motor geometries quickly. This paper introduces a general magnetic circuit model of the mutually coupled SRM that adapts to any geometry, unlike existing geometry-dependent approaches (such as finite elements), which are numerically intensive and require excessive computation time. The model uniquely implements the magneto-motive force (mmf) sources necessary to accommodate complex flux paths through the machine and includes the effects of magnetic saturation. The results are compared to those of a finite element solver to demonstrate the performance of this method as a first-step to evaluating candidate designs     

电流自适应控制抑制开关磁阻电机转矩脉动

开关磁阻电机(SRM)的强非线性源自其双凸极结构、磁路非线性和脉冲供电方式。传统控制多采用SRM线性转矩模型求得参考电流,导致其运行时转矩脉动大。提出基于转矩偏差的双权值神经网络(DWNN)自适应PID控制与基于有限差分扩展卡尔曼滤波(FDEKF)预测电流的前馈补偿控制相结合的SRM控制策略。(1)加入偏差预处理,对转矩偏差进行非线性处理,实现"小误差,大增益,大误差,小增益"的控制,以此为基础进行双权值神经网络自适应PID的电流控制;(2)采用预测电流,构成参考电流的前馈补偿控制,提高控制系统一步预测能力。基于有限差分扩展卡尔曼滤波预测电流,将其与参考电流之差实时补偿参考电流,优化得到恒转矩下有效的控制电流,间接实现总转矩的有效控制。仿真结果证明所提控制策略能有效抑制SRM的转矩脉动。     

Failure Mode Avoidance of Solid Rocket Motor Pressure Monitoring Joint Seals

The sealing joints used for pressure monitoring of solid propellant rocket motors (SRMs) of launch vehicles are very critical, as they are large in number, and leak through any of them is a single point failure mode. Identification of failure modes and its prevention is the key for reliable performance of an SRM. Failure modes are identified and the failure mechanisms of different seals in the pressure monitoring system studied through investigative tests with deliberately induced variations in the design parameters and nonconformance. Systematic analysis is carried out for the proposed designs through a failure mode effects analysis (FMEA), failure modes ranked in accordance with Risk Priority Number (RPN) and reliability of the joints worked out from the data. Design concerns are analyzed, alternate designs explored and innovative design solutions evolved. The effectiveness of the final design is brought out quantitatively by reduced RPN ratings and quantum jump in the reliability. Critical design, process and quality control parameters were identified, and procedures to ensure them evolved for failure mode avoidance.