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.     

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.     

Switched Reluctance Motor Design Using Neural-Network Method With Static Finite-Element Simulation

The paper describes a neural network method for optimal design of a switched reluctance motor (SRM). The approach maximizes average torque while minimizing torque ripple, considering mainly the stator and rotor geometry parameters. Before optimization takes place, an experimental validation of the SRM model, based on the finite-element method, is performed. The validation predicts average torque and torque ripple characteristics for several motor configurations while stator and rotor pole arcs are varied. The numerical results are highly nonlinear, and a function approximation of the data is therefore difficult to implement. We therefore interpolate the data by using a neural network based on a generalized radial basis function. The computed results allow us to search for optimum motor parameters. The optimum design was confirmed by numerical field solutions.     

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.     

Direct instantaneous torque control of switched reluctance machines using 4-level converters

Direct instantaneous torque control (DITC) of switched reluctance machines (SRMs) using a novel 4-level converter is presented. The described DITC control strategy proposes detailed torque control regions and suitable control schemes. Using the 4-level converter, DITC can overcome voltage limitation of asymmetric converters and has a fast magnetisation and demagnetisation to improve dynamic performance and efficiency. For integrated advantages of DITC and 4-level converters, a suitable control scheme is described and analysed. Finally, the proposed DITC method of SRM drive systems using the 4-level converter is verified by simulation and comparative experiments.     

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.     

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.     

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     

DSP-Based Automated Error-Reducing Flux-Linkage-Measurement Method for Switched Reluctance Motors

The switched reluctance motor (SRM) has received considerable attention from researchers for its many inherent advantages, and thus, it has become a popular research topic in the field of variable-speed drives as well as servo drives. Research on SRMs mainly includes their design, modeling and performance analysis, control, as well as applications. However, for verification of design, performance prediction, as well as development of a high-performance sensorless control algorithm, accurate measurement of the magnetic characteristics of the SRM is most critical. Hence, one of the most important problems in the field of SRMs is a practical and accurate instrumentation system for the measurement of the SRM magnetic characteristics. This paper first describes an accurate and fully automated digital method for the measurement of the magnetic characteristic of SRMs, which includes online offset-error removal and winding resistance estimation. In this method, a digital-signal-processor-based virtual instrumentation for measurement of flux linkage is developed. Then, the results of the measurement conducted on a four-phase SRM are presented. The accuracy of the measurement system is verified by comparing with that found via a magnetic analyzer. Finally, the various sources of errors and their contributions to the errors are discussed. The scheme can also be used, in general, for transformers or inductors.     

New procedures for minimizing the torque ripple in switched reluctance motors by optimizing the phase-current profile

This paper introduces five new optimization procedures for the minimization of the torque ripple in the switched reluctance motor (SRM). These new procedures are based on the optimization of the phase-current profile. Two optimization techniques, the simplex method and the genetic algorithm, are adapted to these optimization procedures. The paper compares an older optimization procedure, the optimum harmonic current injection procedure, and the new optimization procedure, and presents conclusions.     

Modeling and Simulation of the Tracked Pipe Duct Cleaning Robot Based on the Pro/Engingeer and RecurDyn

In order to solve the problem of the pipeline inspection and cleaning, combining the 3D modeling software Pro/Eningeer （Pro/E） and the dynamics analysis software RecurDyn, the main model, the track system model of the tracked pipe duct cleaning robot and the road model are built, and the entity assembly in RecurDyn is applied and the simulation model is obtained. The paper RecurDyn. The speed, the torque of driving wheel and the carries out the dynamic simulation with the software vibration-acceleration of gravity of the whole robot in the vertical direction are obtained and analyzed. Finally, the simulation and the calculation results are compared, the two results are basically the same, it has guiding significance for the further study and the potential applications of the tracked pipe duct cleaning robot     

An Analytical Circuit Model of Switched Reluctance Motors

We have developed a dynamic analytical circuit model to simulate the performance of switched reluctance motors (SRMs). Our model expresses flux linkages as multiple decoupled one-argument functions, either current dependent or rotor position dependent, instead of one two-argument function dependent on both current and rotor position. We propose a novel approach for the computation of the air gap permeance at various rotor positions. By using this analytical model, the performance of a SRM can be simulated very efficiently and with improved accuracy. As an application example, we present a simulation of an 8/6 pole SRM in the system domain, and compare the results with transient finite element analysis (FEA) solutions.      

Flextensional ultrasonic motor using the contour mode of a square piezoelectric plate

This paper presents the design, fabrication, and characterization of a new type of standing wave piezoelectric ultrasonic motor. The motor uses a metallic flextensional amplifier, or cymbal, to convert the contour mode vibrations of a square piezoelectric ceramic plate into flexural oscillations, which are further converted to produce rotary actuation by means of an elastic-fin friction drive. The motor operates on a single-phase electrical supply. A beryllium copper rotor design with three-fin configuration was adopted, and the geometry was varied to include different material thicknesses, fin lengths, and inclinations. The best stall torque and no load speed for a 25-mm square motor were 0.72 Nmm and 895 r/minute, respectively. The behavior of the stator structure was analyzed by ANSYS finite element software using harmonic and modal analyses. The vibration mode estimated by finite element modeling (FEM) was confirmed by laser Doppler vibration measurements.     

Modelling and predicting of a switched reluctance motor drive using radial basis function network-based adaptive fuzzy system

A novel fuzzy-neural system, which is referred to as a radial basis function network-based adaptive fuzzy system (RBFN-AFS), is presented, to model the switched reluctance machine (SRM) and predict the dynamic performances in an SRM drive system. First, we use an indirect method to measure the phase flux linkage of a 6/4 SRM and then use the co-energy method to calculate phase torque characteristics. Secondly, the RBFNAFS is designed to learn and train the SRM in the knowledge of the electromagnetic characteristics by using the hierarchically self-organising learning algorithm. This modelling scheme does not require any prior information about the SRM system apart from the input and output signals, and has good capability of generalisation and excellent convergent speed. Then, an RBFN-AFS current-dependent inverse flux linkage model and an RBFN-AFS torque model are used to simulate the various transient and steady-state performances of the 6/4 0.55 kW SRM. The simulation and experimental results based on a DSP drive platform are reported to show that the modelling scheme has good estimation performance under different operation conditions of the SRM.     

Comparison Between Finite-Element Analysis and Winding Function Theory for Inductances and Torque Calculation of a Synchronous Reluctance Machine

This paper compares the prediction of two independent methods for calculating electromagnetic torque and inductances of a synchronous reluctance machine under linear condition. One method is based on winding function analysis (WFA) and the other on finite-element analysis (FEA). Both methods take into account the rotor geometry, the stator slot effects and the stator winding connections. The simulation results obtained by the WFA are compared with the ones obtained by two-dimensional FEA. It is shown that the two methods give approximately the same results but require different computation times.     

Preparation of Reference Material 8504, Transformer Oil

A new reference material (RM), RM 8504, has been prepared for use as a diluent oil with Aroclors in transformer oil Standard Reference Materials (SRMs) 3075 to 3080 and SRM 3090 when developing and validating methods for the determination of polychlorinated biphenyls (PCBs) as Aroclors in transformer oil or similar matrices. SRMs 3075-3080 and SRM 3090 consist of individual Aroclors in the same transformer oil that was used to prepare RM 8504. A unit of RM 8504 consists of one bottle containing approximately 100 mL of transformer oil. No additional constituents have been added to the oil.     

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.     

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.     

High-performance current control for switched reluctance motors based on on-line estimated parameters

To reduce torque ripple in a switched reluctance motor (SRM) by current profiling, a high-performance current controller is necessary. This study presents a high-performance current controller for SRM drives. A Bspline neural network is used to model the non-linearity of the SRM and estimate back electromotive force (EMF) and incremental inductance on-line in real time. The on-line modelling scheme does not require a priori knowledge of the machine?s electromagnetic characteristics. Based on the on-line estimated parameters, a current controller with adjustable PI gains and back-EMF decoupling is implemented. The performance of the current controller has been demonstrated in simulation and experimentally using a four-phase 8/6 550 W SRM drive system.     

Driving mechanism, design, fabrication process, and experiments of a cylindrical ultrasonic linear microactuator

A new type of cylindrical ultrasonic linear microactuator (CULMA) is introduced. The traveling wave generation condition in the stator is presented, which was confirmed using simulation and experimentation. The design and fabrication process to develop the stator is described. The stator was successfully fabricated using metallic glass and a sputtering method, and the vibration of the prototype matched the simulation results. When the driving frequency is at 626 kHz, the traveling wave in the stator was observed. Loaded with a pipe slider, the slider movement was experimentally demonstrated and the motion measured with 26 mm/s in peak speed. This paper presents a traveling wave generation method in a CULMA which would also available in other microactuators or MEMS-scale ones.