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Analysis and characterization of switched reluctance motors: Part I ynamic, static, and frequency spectrum analyses
... Recently, Srinivas [110] has explored two software applications electromechanical structure system (EMSS) and power system computer-aided design (PSCAD) for modeling and simulating the dynamic characteristics of switched reluctance motor through co-simulation. The per-phase model of SRM in EMSS and the block diagram for dynamic characterization using PSCAD along with the waveforms for a load of 0.5 N-m is shown in Figs. 8, 9, and 10. ...
... Complete per-phase model of SRM using EMSS for dynamic analysis[110]. ...
... Block diagram of dynamic characterization of SRM by means of PSCAD[110]. ...
Switched reluctance machines have emerged as an important technology in industrial automation; they represent a real alternative to conventional variable speed drives in many applications. This paper reviews the technology status and trends in switched reluctance machines. It covers the various aspects of modeling, design, simulation, analysis, and control. Finally, it discusses the impact of switched reluctance machines technology on intelligent motion control.
... The torque curves characterize the SRM. These can be obtained with different techniques [18][19][20][21]. In this study, the SRM static torque was measured. ...
... Now, the behaviour of the system is directly related to the switching function dynamic and the reaching law. Performing the appropriate substitutions of (21) in (25), one obtains expression (26) that will be implemented in the microprocessor control system. ...
Abstract This paper presents a study about the angular position control of a regular four phases 8/6 Switched Reluctance Machine (SRM). The SRM has very interesting characteristics, however there is still not a comprehensive use of it as a position controlled system. Effectively there are many papers in the literature about position detection but still few about SRM position control. This work pretends to be a contribution to overcome this limitation. The theoretical development and design of a robust and accurate sliding mode controller (SMC) is presented, based on the machine torque characteristics, with the correspondent experimental implementation based on the construction of a prototype. It is a low cost system, which makes it very attractive and competitive in the market of drive systems for industrial processes. Experimental tests were done in order to validate the theoretical development. The performance and dynamic behaviour of the SRM system with angular position control is presented and discussed.
... The first and most accurate approach is to use transient finite element analysis (FEA) coupled with a driving circuit [1]- [7]. The second approach is to use magnetostatic FEA to derive the phase flux linkage as a function of the phase current and the rotor position in the form of a lookup table; then the performance is computed using a circuit simulator [8]- [10]. Due to the high computational resources required by FEA, these two approaches are usually applied during the final validation stage of the design process. ...
... The traditional method uniformly divides the slot area into flux tubes in such a way that all flux tubes are parallel to the slot bottom; the proposed method divides the slot area into flux tubes via an optimization process to get maximum energy, as shown in Fig. 8. When P moves from A to B, the total permeance in the area ABCDA is (6) where is computed based on (A-23) with (7) and is computed based on (A-12) with (8) where and are current areas in the two subregions. The permeance with P moving from A to B is shown in Fig. 9. ...
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.
... The phase current waveform of FEA seems to be closer to ideal current wave shape as ideal material properties are incorporated in the electromag-netic FEA while measured waveform is due to imperfections in the fabricated machine geometry and variations in the material property of SMC pre-form blanks employed in the fabrication. The comparison of measured and FEA predicted hot spot temperature rise in stator core of SMC prototype is given in Table 3. FEM helped to obtain the static and dynamic electromagnetic characteristics [1,4] through simulation. ...
Soft Magnetic iron powder material and electromagnetic devices based on it underwent prominent development. Basis for soft magnetic composites is tightly packed iron powder using a die into a solid material. However, the properties will in most cases be different from those obtained from compaction and machining process. This paper addresses the development of a switched reluctance machine
(SRM) employing pre-form iron powder blanks (Somaloy 1000 3P) of low mass density to address the vibration and acoustic noise issues. This can be a fast and low cost approach which aim to machine
the components from a pre-form blank. Finite Element Analysis (FEA) study has been conducted to determine key parameters which can be validated through experiments on the prototype motor.
... The static and dynamic electromagnetic characteristics [1,5] have been obtained through FEA. MagNet 6.1.1 ...
Soft Magnetic Composite (SMC) materials possess isotropic magnetic and thermal properties, very low eddy current loss and relatively low total core loss at medium and higher frequencies. This paper presents the application potential of iron powder SMC in switched reluctance machine (SRM) and its performance enhancement. The results of extensive finite element simulation and experimental validation of the proposed fabricated prototype are delineated. The study concludes that the use of SMC as magnetic core of a switched reluctance motor enhances its thermal and vibration characteristics in comparison with the conventional lamination counterpart.
... FEM is a useful tool during machine design and prototype testing, reducing manufacturing costs and experimental testing. Over the years, many papers have used FEM to model SRMs through several software (Xu and Torrey 2002; Parreira et al. 2005;Srinivas and Arumugam 2005). Parreira et al. (2005) compare the FEM results for several currents with the experimental data, and noticing a significant difference for low currents compare the experimental B-H curve with that used in the FEM simulation. ...
The main objective of modeling a switched reluctance machine is to derive a mathematical function to relate the outputs to the inputs. Due to the nonlinear relationship between the variables of torque, flux linkage, current and angular position of the rotor, Switched Reluctance Machine (SRM) modeling is a very challenging task and an open problem. Modeling is usually done in two situations, modeling a single machine, or modeling a set of machines. Each one must fulfill different requirements. This work presents a survey of different SRM modeling approaches, evaluating its advantages and limitations when modeling a single machine or a set of machines.
... The static and dynamic electromagnetic characteristics [1,5] has been obtained using Finite Element Analysis (FEA) simulation studies. The finite element mesh along with the flux lines plot at the aligned position obtained through circuit coupled finite element analysis is shown in Fig.4 while the torque profile for SRM-SMC1000 motor is shown in Fig.5. ...
Soft magnetic composite (SMC) materials characterized by three dimensional isotropic ferromagnetic behavior and very low eddy current losses find utility in complex geometry electrical machines due to flexible machine design and assembly.The suitability of soft magnetic composite material in switched reluctance motor (SRM) has been investigated through static, dynamic, thermal, vibration and acoustic noise characterization. Extensive Finite Element (FE) and coupled field analysis study has been carried out on three configurations viz (a) SRM made of Sheet Steel (SRM-M19)(b)SRM made of Soft Magnetic Composite material 500 (SRM-SMC500) and (c)SRM made of Soft Magnetic Composite material 1000 (SRM-SMC1000) and few test results are presented.
... It is thus necessary to keep the temperature of the machine components within permissible bounds for safety performance. Due to this, thermal analysis plays prominent role in the analyses of electrical machines [3]. There are two basic types of thermal analysis of electric machines: Analytical lumped-circuit and numerical methods. ...
... It is thus necessary to keep the temperature of the machine components within permissible bounds for safety performance. Due to this, thermal analysis plays prominent role in the analyses of electrical machines [3]. There are two basic types of thermal analysis of electric machines: Analytical lumped-circuit and numerical methods. ...
The purpose of this paper is to observe the heat distribution inside the Switched Reluctance Machine (SRM) through Computational Fluid Dynamics (CFD). Electromagnetic losses such as copper and core losses are considered as the heat sources in the machine. Initially, a three dimensional (3-D) steady state thermal analysis is carried out to determine the film coefficient of machine parts. Further, a transient thermal analysis is performed to predict the temperature rise. From the transient analysis, heat distribution for the given speed and time taken to reach the steady state are observed.
... The magnetization characteristic can be obtained by magnetostatic FEA (1)- (3) or by measurements done on the existing machine. However, both methods are not particularly suitable to implement during initial stages of the machine's design process. ...
This paper describes a fast analytical model for computing the nonlinear magnetization and static torque characteristics of a switched reluctance machine (SRM). This model is developed using the flux-tube and gage-curve methods. The proposed model is used for computing the magnetization (flux-linkage) and torque characteristics of three and four-phase SRMs. The simulation results obtained using the proposed analytical model are compared to those obtained using magnetostatic finite-element analysis (FEA) for a three-phase 12/8 SRM and for a four-phase 8/6 SRM. Finally, experimental verification of the analytical model is presented for the 12/8 SRM and 8/6 SRM prototypes.
... The requirement for predicting the steady state and dynamic performance of SRM is to generate its magnetization characteristic ψ(I, θ) and torque lookup table T(I, θ), where ψ is the flux linkage, I is the excitation current, θ is the rotor mechanical angular position, and T is the torque. The magnetization characteristic can be obtained by magnetostatic FEA [1]–[3] or by measurements done on the existing machine. However, both methods are not particularly suitable to implement during initial stages of the machine's design process. ...
This paper describes fast analytical model for computation of the switched reluctance machine's (SRM) nonlinear magnetization characteristic and torque lookup table. The flux-tube and the gage-curve methods are used to develop this fast analytical model. Presented model is used for computation of the magnetization characteristic and torque lookup table of three and four-phase SRMs. The simulation results obtained using proposed analytical model are compared to the results of magnetostatic finite-element analysis (FEA) for a three-phase 12/8 SRM. Experimental verification of the analytical model is also presented for the same 12/8 SRM prototype.
... It may not be necessary to design for periods of multi-phase conduction. Assuming that phase-a is under consideration, the voltage equation with this converter is written as, [5,6,7] ( ) ...
This paper presents a new approach to the automatic control of the turn-off angle used to excite the Switched
Reluctance Motor (SRM) employed in electric vehicles (EV). The controller selects the turn-off angle that supports and improves the performance of the motor drive system. This control scheme consisting of classical current control and speed control depends on a lookup table to take the best result of the motor. The turn-on angle of the main switches of the inverter is fixed at 0o and the turn-off angle is variable depending on the reference speed. The motor, inverter and control system are modeled in Simulink to demonstrate the operation of the system.
... In both cases, as mentioned above, there is a flux building interval from θ On to θ off , called dwell, and the interval where both mosfets are switched off and the flux decays to zero [5,6,7]. ...
This paper presents a new approach to control the turn-off angle θoff used to excite the Switched Reluctance Motor (SRM) used in electric vehicles (EV). The controller selects the turn-off angle which will improve the performance of the electric drive system with turn-on angle constant. This control scheme consisting of classical current controller and speed controller depend on lookup table to choose the best result from it. The turn-on angle of the main inverter switches is fixed at 0° and the turn-off angle is variable depending on the reference speed and PI current controller. The whole system including motor, inverter and control unit are modeled in Simulink to demonstrate the operation of the system.
... The curves of the torque that characterize the SRM can be gotten through some ways [8,9]. In this study it was done by experimentally measurement of the static torque. ...
The switched reluctance machine (SRM) was, during the last decade, target of the attention of researchers. Some studies stand out the application potentialities of the machine, another's developed the machine design for better performance in terms of efficiency, good torque and speed behavior. Others denote the possibility of good machine functioning without the position sensor and there are still others presenting a way to reduce the noise produced in dynamic regimen. However, there are very few works about the analysis of the machine behavior regarding its shaft position. This work presents some results in this thematic, studying and analyzing its geometry and torque values necessary to develop when a shaft position is intended. Some methodologies are presented in order to be applied to obtain a shaft position. One of them is based on experimental results taking into account the two phases that are necessary to excite simultaneously in order to produce the immobilization of the motor shaft in one determined position.
... Torque curves characterizing the SRM can be obtained with different techniques [6,7]. In this study, the SRM static torque was measured. ...
The switched reluctance machine (SRM) was, during this last decade, the target of various researchers' attention. Several authors have published mainly research results analysing torque ripple reduction, speed control, noise reduction, magnetic characteristics, and the SR machine operation without position sensor. However, very few works have studied the SR machine in terms of its shaft position. This paper presents this thematic. The static torque, experimentally obtained, is analysed followed by the determination of which phases must be excited in order to immobilize the shaft. Finite element method (FEM) is used to calculate the current values, function of the various shaft positions. Experimental tests were done in order to validate the theoretical assumptions and FEM results. Finally, the results are discussed.
This paper presents soft computing-based optimization techniques for the cogging torque reduction and thermal characterization by finite element analysis in a permanent magnet brushless DC motor (BLDC). Stator and rotor structure of BLDC motor are optimized to reduce the cogging torque, noise, and vibration by using the design parameters namely: length of magnet, length of air gap and opening in the stator slot which are selected by performing variance-based sensitivity analysis. The proposed method is suitable in the preliminary design phase of the motor to determine the optimal structure to improve the efficiency. The comparison of results obtained using firefly algorithm , ant colony optimization algorithm and Bat algorithm indicate that Firefly-based optimization algorithm is capable of giving improved design parameter output. Cogging torque is created due to the interaction of magnets in the rotor and the stator slot of the motor. Thorough thermal analysis is also conceded out to investigate the thermal characteristics at dissimilar portions of the motor namely: stator core, stator slot, rotor core and permanent magnet at different operating environments in the continuous operation mode. Thermal investigation is required for the various high speed e-vehicle applications. The usefulness of the designed machine simulation is compared with the results obtained from hardware analysis. The outcomes attained from software simulation studies are validated through experimental hardware setup.
This paper presents the electromagnetic analysis, vibration analysis and thermal analysis of a 6/4 pole, 1.1 kW switched reluctance motor (SRM), focusing on its application to EV, in the sense that the vibration and thermal analyses are carried out at speeds of range more than 1000 rpm, which usually experienced by EV SRM. At first, electromagnetic analysis is performed for six different silicon steel materials viz., 35JN210, 35JN300, 50JN470, 50JNA350, 50JNA600 and 50JNE350, and from the results, it has been noted that the material 35JN210 has less torque ripple and a good efficiency compared to all other materials. So this material is selected for SRM structure to perform thermal and vibration analysis. SRM proves to be a suitable candidate in electric vehicle application with the limitation with respect to its vibration and noise. The noise generation during motor operation is a major concern for SRM. The main source of vibration, the radial force, is calculated using two- dimensional (2D) transient finite-element analysis (FEA).The electromagnetic analysis is performed to find out the force exerted on the stator and deformations due to that. Using these nodal forces as input, transient analysis is performed to examine the motor's vibration characteristics. By this analysis, the motor modal frequencies are examined so that the motor operation could be skipped from operating in this vibrating region when it is used in electric vehicle applications. For thermal analysis, FEA is used to calculate the heat generation and temperature distribution on different parts of the machine to estimate the thermal behaviour of the motor.
PurposeThis paper presents a contemporary direction on the reduction of vibration and acoustic noise in Switched Reluctance Motor (SRM) using Soft Magnetic Composite (SMC) blank.Methods
Soft magnetic composite materials are composed of iron powder and resin. The particles are compacted, together with a lubricant and possibly a binder, at high pressure into a bulk material. Soft magnetic composite materials are characterized by three-dimensional isotropic ferromagnetic behaviour and very low eddy current loss. The competence of Soft Magnetic Composite (SMC) material in Switched Reluctance Motor (SRM) on vibration related issues has been investigated through Finite Element Analysis and experimentation.ResultsTo analyze the magnetic, vibration, and acoustic noise characteristics two motor configurations, viz., M19-SRM (M19- Switched Reluctance Motor) and SMC–SRM (Soft Magnetic Composite - Switched Reluctance Motor) are considered.Conclusion
The efficacy of SMC–SRM (Soft Magnetic Composite - Switched Reluctance Motor) prototype in vibration mitigation has been validated.
This paper describes a real-coded GA-based fuzzy controller for controlling speed of the sensorless switched reluctance motor drive. The sensorless operation was modeled using minimal neural network with flux and current as the input and rotor position as output variables. The controller consists of fuzzy controller and real-coded GA. The input, output scaling factor and membership function boundary values of fuzzy controller and turn-off angle of motor are tuned by real-coded GA using the minimum speed error is considered as the fitness function. The proposed control algorithm has been simulated in MATLAB and implemented using TMS320F2812 DSP controller and tested with 1 hp, 8/6 SR motor. To demonstrate the effectiveness, the results of the proposed real-coded GA-based fuzzy controller is compared and analyzed with conventional proportional integral controller and fuzzy controller. Both simulations and experimental results prove that the proposed controller performance is better in terms of steady state response, dynamic response, and robustness than the conventional control methods. The vibration analysis clearly shows that the proposed system will minimize the vibration on motors.
This paper introduces a switched reluctance generator (SRG) made from soft magnetic composite (SMC) material .The soft magnetic composite switched reluctance generator prototype has been fabricated using SOMALOY1000 pre-form blanks utilizing indigenous machining process. The machine geometry has been chosen to utilize maximum material of the procured prototyping blanks with the due care taken to ensure that the geometry adheres strictly to the established design conventions for a switched reluctance machine. The performance has been analysed through circuit coupled finite element analysis taking into account mutual flux. The fabrication details are expounded tersely along with the results of real time thermal analysis carried out on the developed prototype.
This paper presents a novel analytical model for computation of the switched reluctance machine's (SRM) nonlinear magnetization characteristic and torque lookup table. The flux-tube and the gage-curve methods are used to develop the novel analytical model. Presented model is used for computation of the magnetization characteristic and torque lookup table of three and four phase SRMs. The simulation results obtained using proposed analytical model are compared to finite-element method (FEM) results. Experimental verification of the analytical model is presented for an 8/6 SRM.
In this paper, control of Switched Reluctance Motor by control of firing angles and the effect of variations of stator pole arc for Torque Ripple Reduction is reviewed. Steady state dynamic characterizations of basic switched reluctance motor 6/4 are calculated for three different sizes of stator pole arcs. The results of dynamic analysis indicates that steady state performance of SRM is improved with using of the control of firing angles and stator pole arc being increased by pole shoes. Two-Dimensional Finite Element Method (2D FEM) is utilized to model and control strategies of Switched Reluctance Motor.
In this paper, processing the static modeling of Switched Reluctance Motor 6/4 with three different stator pole arcs sizes are described. The result of static analysis, including inductance, flux linkage, and static torque vs. rotor position for various current excitations by considering saturation effect in three states of motor with and without stator pole shoes are investigated. The effect of the increase in stator pole arcs is presented for improving SRM performance. Finally, two existing methods of inductance calculation in the finite element analysis package of ANSYS are reviewed and their results are compared.
The traditional signal analysis method couldn't supply the part time-frequency characteristics of saltation signal. This paper analyzes the theory of fault line detection of non-effectively earthed neutral system based on modulus maximum determining polarity. A simulation of the non-effectively earthed neutral system is built here. It verifies the correctness and practicability of the method which is used in fault line detection, and shows a way of how to choose the wavelet function and the character scale. All of the results in this paper present a plausible way to transient protection and fault line detection.
This paper presents the design optimization of switched reluctance motors (SRMs). The design goals are high average torque,
low torque ripple and low mass under the constrained phase current of SRMs. To achieve these goals, we design not only the
geometries of SRMs using topology optimization, but also voltage on–off angles. The performance analysis of SRMs is carried
out to predict the torque profile. Fourier series expansion is used to obtain the explicit expression of inductance curves,
which allows us to perform the analytical design sensitivity analysis of the torque profile. The optimization problem is solved
using the sequential linear programming (SLP) method. In the optimized geometry, the arc lengths of poles are increased with
the notched shape near airgap, and the holes inside the rotor are created. In addition, the mechanical characteristics of
the optimized SRM are investigated using the modal and thermal analysis by MSC/NASTRAN.
KeywordsTopology optimization-Finite element methods-Fourier series expansion-Switched reluctance motors
This paper present a new approach to the automatic control of the turn-off angle used to excite the switched reluctance motor (SRM) for electric vehicle (EV). The controller selects the turn-off angle that supports the most speed operation of the motor drive system. This control consists of classical current control and speed control depends on lookup table to take best result of the motor. The turn-on angle of the main switches of inverter is fixed at 0deg and the turn-off angle is variable depend on the reference speed. The motor, inverter and control system are modeling in Simulink to demonstrate the operation of the system
Developing a precise system simulation model is a critical step in the design and analysis of optimal control strategies for a switched reluctance motor (SRM). To achieve this objective, the following works have been done in this paper. 1) A 3-D FEA model based on double scalar magnetic potential method (DSMP) is developed for obtaining the distributions of SRM magnetic field, then the flux linkage characteristics are calculated by using enhanced incremental energy method (EIEM). 2) In order to enhance modeling accuracy of the nonlinear flux linkage, a new RBF neural network with boundary value constraints (BVC-RBF) is used for approximating, based on the calculated flux linkage data. 3) The nonlinear BVC-RBF based simulation model of the SRM system is established for dynamic analysis with the power system block (PSB) modules of Matlab/simulink. 4) Simulation and experimental results are presented and compared for model validation. The validation study indicates that the developed model is highly accurate.
The goal of this research is to investigate an approach to find the optimal geometry of electric motors for the enhancement of force/torque performance. To predict the magnetic force/torque of electric motors having complex structure, the finite element method for magnetostatic analysis is extensively investigated. The finite element formulations for two/three dimensional problems using nodal/edge elements and for non-linear problems with Newton-Raphson iteration, are described in detail. From the obtained magnetic field, the magnetic force/torque can be calculated using various methods: Maxwell stress tensor method, virtual work method, equivalent source method, body force calculation method using the virtual air-gap scheme. Their formulations are briefly derived for both linear and non-linear problems. The observation of force calculation results confirms that total magnetic force is consistent regardless of calculation methods, but local force distribution depends on calculation methods.
The structural topology optimization approach is applied to find optimal geometries in magnetic field problems. As a basic study, two optimization examples are presented. The first example aims to examine the properties of a magnetic circuit with respect to the force/torque performance. In the second example, the structural topology optimization is employed in a coupled magneto-structural problem. The mechanical compliance caused by the distributed local magnetic force is minimized when maximizing the global magnetic force. The design results reveal that different force distributions, depending on calculation method, result in the completely different optimal geometry in the magneto-structural problem.
As a practical application, switched reluctance motors are designed using structural topology optimization. The design goal is to minimize torque ripple under the constrained current. To represent motor performance in a steady-state operation explicitly, the mathematical analysis model is newly developed. Magnetic characteristics are modeled using the finite element method and interpolation functions. Then, the current curve is calculated by solving the circuit equation, and the torque profile is obtained from the global virtual work method. Using the sequential linear programming method, the rotor/stator shape and voltage on-off angles are designed to improve torque performance. Two/three dimensional designs in the linear B-H relation and the design considering the nonlinearity due to magnetic saturation are presented.
Variable Speed Drives (VSDs) are the most effective means for energy saving in many practical applications particularly in pumps, fans, compressors conveyors, etc. Up to now the only wide used VSD is a frequency controlled electric drive with AC induction motor. A Switched Reluctance Drive (SRD) having noticeable advantages such as simple construction, low cost, high reliability, high efficiency, etc. still does not compete with traditional AC drives mainly because of the following unsolved problems: complexity of proper control, necessity of a rotor position sensor, poor acoustic characteristics. Results of R&D project realized in Moscow Power Engineering Institute in co-operation with Jaroslavl Electric Machine-Building Plant allowed to overcome the above mentioned problems and to obtain reliable low cost sensorless SRD with high efficiency and acceptable acoustic characteristics. The original sensorless SRD version is based on current measuring and exploiting a specially organized observer that provides a stable drive operation within broad speed-torque ranges. Acoustic SRD characteristics were improved by means of proper current pulses shape control. Small increasing the time of current pulse trailing edge allowed to decrease the noise level to 70 dB(A) and brought the SRD to a vary smooth operation even at a low speed.
The paper presents a new method for accurately calculating the torque and current of a variable-reluctance stepping motor from measured or computed flux-linkage/current/rotor position data. The new method is more accurate and uses less input data than previously known procedures, and is computationally efficient. It can be applied to both steady-state and transient problems.
A methodfor calculatingthe dynamic characteristics of the SwitchedReluctance Motor (SRM) has been proposed. The inductance of the SRM, which varies with rotor position and excitation current and which solely determines the dynamic performance of the machine, has been estimated from Finite Element Analysis (FEA). A circuit simulation for the dynamic characterization of SRM is performed in the Maxwell SPICE environment using the power of an Electromechanical Structural System (EMSS) tool. An integral approach for electromagnetic field computation coupled with circuit simulation is proposed for the dynamic performance prediction of SRM. Detailedsimulation results for various loadconditions are the highlight of this article. Further, the simulations are compared with equivalent simulations done using pSPICE.
It is now 150 years since Wheatstone demonstrated the first reluctance motor. This article outlines the recent significant advances in switched-reluctance motor drives which now make them serious contenders not only to inverter-fed machines but also to the established DC-motor drive
The variable-reluctance or switched-reluctance motor has some remarkable characteristics that make it attractive for dozens of applications. With CAD software now available, and many prototypes established, there should be few technicalbarriers between the laboratory and a number of successful niches in the drives market
The paper describes the use of a 2-dimensional finite-element field analysis (FEA) to obtain N¿/i/ rotor position characteristics of a doubly salient switched reluctance motor. The stator and rotor have even but unequal numbers of poles. Unlike the single tooth per pole construction of the most common doubly salient pole motors, the motor considered for analysis has two teeth per stator pole. The increase in torque developed due to the multitooth stator pole configuration has been reported by Finch et al. in May 1984. An accurate knowledge of flux pattern inside the motor is essential to a machine designer for performance prediction. The complex configuration and material nonlinearities of the motor makes analytical methods of magnetic field analysis difficult. The numerical method (FEA) used gives a better understanding of the flux distribution inside the motor. The terminal inductance per phase, the flux linkage of each stator pole winding, and the components of the leakage inductances are determined for different rotor positions and excitation currents. The average torque developed by the motor is also determined under current forced conditions.
The paper explores the theory and potential of a family of doubly salient electronically-switched reluctance motors. It is demonstrated that the machine provides the basis for fully-controllable variable-speed systems, which are shown to be superior to conventional systems in many respects. The motor retains all the advantages normally associated with induction motors and brings significant economy in the drive electronics. The basic modes of operation, analysis, design considerations and experimental results from a range of prototype motors up to 15 kW at 750 rev/min are described. The most recent prototype has achieved a continuous rating which is 1.4 times that of the equivalent induction motor.
A method for calculating the dynamic characteristics of switched
reluctance motor (SRM) has been proposed. The inductance model of SRM
that is changed following the rotor position can be estimated from FEM
analysis. Based on the model, we design a circuit simulation of SRM
using SPICE, which can simulate voltages, currents, torque and rotation
speed of the SRM
This paper reports on three unique methods to improve the torque
profile of the switched reluctance motor. The improved stages carried
out on the electromagnetic analysis of two - dimensional (2-D) finite
element analysis via the mesh refinement process is first presented. The
study of rotor geometry modifications is the next method; the importance
of rotor pole shaping is justified through rigorous analysis. Simulated
torque profiles from the rippled to the smoothened are presented. In the
third method achieving a smooth torque profile by the introduction of
pole shoes in the stator poles is reported
The author describes the basic operating principles of switched
reluctance motors and the basic drive configuration and circuits
including power converter switching arrangements. The author then
discusses inductance variation, current waveforms and control. The
theoretical model and analysis of the drive is given and the efficiency
and performance discussed. Applications are also briefly discussed
A new control IC for switched reluctance motor drives is
described. The LMB1008 contains all the necessary analog and digital
control to drive a switched reluctance motor in both forward and reverse
rotation with stepwise-adjustable firing angles. Both motoring and
braking modes are provided. The internal commutation logic can operate
with shaft position signals derived from either 3 or 2 Hall or optical
sensors; or in `straight-through' mode with no shaft position sensors.
For closed-loop speed control an internal tacho (frequency-to-voltage
converter), oscillator, error amplifier, and PWM generator are provided.
A comparator is also provided for excess current detection and current
limiting. The IC is implemented in National Semiconductor's BLOCCS
process technology. Supply voltage range is 7-24 V and the supply
current is 20 mA. The IC has an internal regulated voltage level of 5 V,
and the input voltage levels are TTL-compatible (with pull-up for
open-collector drives). The authors include typical performance data a
waveforms
The sensitivity of the pole-arc/pole-pitch ratio of the stator and rotor on the performance of a switched reluctance motor is investigated. An analytical method based on magnetic flux path and a two-dimensional finite-element analysis are used. The sensitivity study is performed by comparing the average torque developed for different stator as well as rotor pole-arc/pole-pitch ratios and choosing the ratio combination that produces the greatest value of average torque.< >
A method for minimizing the instantaneous torque ripple in
switched reluctance (SR) machines is investigated and implemented. The
method is based on estimating the instantaneous SR motor torque from the
flux linkage versus current and rotor position characteristic curves via
a bi-cubic spline interpolation. These coefficients are computed
offline, stored in a given memory location of the control processor, and
used by two routines that are capable of estimating the rotor position
and electromagnetic torque from the phase voltages and currents. The
estimated output torque is then compared to a constant reference value,
and the result of this comparison drives a current regulator that
generates the proper motor phase currents. The ripple minimization
scheme is simple and does not require a very fast processor. Its
feasibility is confirmed via simulation and some preliminary
experimental results
Optimal precalculation of the position-phase current profile for
current feeding a four-phase, 4 kW switched reluctance motor results in
a single-input, linear, decoupled output torque controller that provides
low torque ripple. A bicubic spline interpolation was used to model the
nonlinear experimental data. The algorithm is based on minimizing both
the average and peak current and hence improves the dynamic performance
of the novel six-switch, current-fed, 4 kW, 40 kHz IGBT inverter. Test
results are presented
The effects that simple variations of the standard rotor pole face profile could have on the torque are examined, basically from an elementary viewpoint of how the modified profiles affect the distribution and magnitude of the radial and tangential components of the flux density. It is observed that the average torque is mostly affected by changes that alter the dominant radial component, such as changes in the effective airgap length. It was also observed that an increase in the average torque can be obtained by a favorable shift in the torque versus angle characteristics by relatively simple changes of the rotor pole profile. Such a shift that reduces the slope of the torque angle characteristic, skewing the curve towards the unaligned position, has two advantages. One is that the phase inductance is at its maximum positive slope, and hence maximum torque, when the phase is energized. The other is that the flatter inductance profile near the aligned position when the phase current is to be commutated allows a faster drop-off of the commutated current, and thus a smaller negative torque.< >
A number of power electronic converter circuits exist for switched
reluctance motor (SRM) drives which are generally applicable to most
loads. A larger number of circuits exist which are suitable for
particular niche applications, but which have the potential to be the
most cost-effective within that niche. Due to the variable methods of
operation of these circuits and the rapid progress in this field,
comparisons of these circuits have so far been limited. This paper
attempts to bring together the sum total of power converter topologies
so far published for SRM drives. A novel classification methodology is
presented. The power converters are compared using a straightforward
total semiconductor VA per phase sum, and the relative cost of the drive
system elements is considered
It is shown how to supply two-time-scale nonlinear control design techniques to switched reluctance motors. A nonlinear dynamic model is developed and decomposed into separate slow and fast subsystems. A feedback control is designed so that, whenever the fast subsystem is at equilibrium, the dynamics of the slow subsystem are input-output equivalent to a second-order transfer function. The use of reduced-order feedback linearization methods leads to improved performance by reducing torque ripple. Experimental results from a laboratory implementation of a position control system are presented. On the basis of measured overshoot, risetime, and settling time, the prototype response is consistent with the desired linear response to within 23% error on average. The transient behavior of the motor can thus be adjusted over a wide range, and in a reasonably predictable fashion, by simply varying the gains of the outermost loop.< >
The switched-reluctance motor is a simple and robust machine which is finding application over a wide power and speed range. To properly evaluate the motor design and performance and the effectiveness of different control schemes, an accurate model is required. The finite-element method can be used to predict the performance of the switched-reluctance motor as it can account for the salient pole geometry of the stator and rotor and the nonlinear properties of the magnetic materials. The computed results are shown to compare favorably with test results from a 7.5-kW Oulton switched-reluctance motor.
This paper describes a new method for indirect sensing of the
rotor position in switched reluctance motors (SRMs) using pulse width
modulation voltage control. The detection method uses the change of the
derivative of the phase current to detect the position where a rotor
pole and stator pole start to overlap, giving one position update per
energy conversion. As no a priori knowledge of motor parameters is
required (except for the numbers of stator and rotor poles), the method
is applicable to most SRM topologies in a wide power and speed range and
for several inverter topologies. The method allows modest closed-loop
dynamic performance. To start up the motor, a feedforward stepping
method is used which assures robust startup (even under load) from
standstill to a predefined speed at which closed-loop sensorless
operation can be applied. Experimental results demonstrate the robust
functionality of the method with just one current sensor in the
inverter, even with excitation overlap, and the sensorless operation
improves with speed. The method is comparable to the back-EMF position
estimation for brushless DC motors in principle, performance and cost. A
detailed operation and implementation of this scheme is shown, together
with steady-state and dynamic transient test results
An example of simulation of a closed loop controlled electric
device that shows the feasibility of simulating the equipment by means
of a general-purpose electronic circuit analysis program is described.
The SPICE program was used because of its well-known facilities for
simulating electronic circuits. A method for extending the SPICE
facilities to simulate the electromechanical energy conversion and the
drive control is reported. The simulation of a switched reluctance motor
drive with closed loop speed control is considered, and the results were
validated by experimental tests executed on an industrial drive
Motivated by technological advances in power electronics and signal processing, and by the interest in using direct drives for robot manipulators, we investigate the control problem of high-performance drives for switched reluctance motors (SRM's). SRM's are quite simple, low cost, and reliable motors as compared to the widely used dc motors. However, the SRM presents a coupled nonlinear multivariable control structure which calls for complex nonlinear control design in order to achieve high dynamic performances. We first develop a detailed nonlinear model which matches experimental data and establish an electronic commutation strategy. Then, on the basis of recent nonlinear control techniques, we design a state feedback control algorithm which compensates for all the nonlinearities and decouples the effect of stator phase currents in the torque production. The position dependent logic of the electronic commutator assigns control authority to one phase, which controls the motion, while the remaining phase currents are forced to decay to zero. Simulations for a direct drive, single link manipulator with the SRM are reported, which show the control performance of the algorithm we propose in nominal conditions and test its robustness versus the most critical parameter uncertainties of payload mass and stator resistance.
improved finite element analysis for electric machines—applied to switched reluctance motors (using cad model)
- arumugam
R. Arumugam and K. N. Srinivas, " Improved finite element analysis for electric machines—Applied to switched reluctance motors (using CAD model), " in Proc. Nat. Conf. Applied System Engineering and Soft Computing. Agra, Uttar Pradesh, India, Mar. 4–5, 2000, pp. 126–131.
a review of switched reluctance motor design
- fulton
N. N. Fulton and J. M. Stephenson, " A review of switched reluctance motor design, " in A Review of Collected Papers on Switched Reluctance Motor Drives, CA: Intertec Communications Inc., 1988, pp. 120–126.
analysis of variable reluctance motor parameters through magnetic field simulations
- konecny
K. Konecny, " Analysis of variable reluctance motor parameters through magnetic field simulations, " in MOTOR-CON Proc., 1981, pp. 2A2.1–2A2.11.
spectrum analysis of torque ripple in a switched reluctance motor
- srinivas
K. N. Srinivas et al., " Spectrum analysis of torque ripple in a switched reluctance motor, " in Proc. Nat. Conf. Elect-2004. Chennai, India, pp. 88–93.
Compatible permanent magnet or reluctance brushless motors and controlled switch circuits
- R D Bedford
R. D. Bedford, " Compatible permanent magnet or reluctance brushless motors and controlled switch circuits, " " Compatible brushless reluc-tance motors and controlled switch circuits, " U.S. Patents 3 678 352 and 3 679 953, 1972.
Design and implementa-tion of linearizing and feedback transformation for switched reluctance motors
- D G Taylor
- M J Woolley
- M I Spong
D. G. Taylor, M. J. Woolley, and M. I. Spong, " Design and implementa-tion of linearizing and feedback transformation for switched reluctance motors, " in Proc. 17th Symp. Incremental Motion Control System Devel-opment, Champaign, IL, 1988, pp. 173–184.
Spice assisted sim-ulation of controlled electric drives
- F Giovanni
- S Piranni
- M Rivaldi
- C Tassani
F. Giovanni, S. Piranni, M. Rivaldi, and C. Tassani, " Spice assisted sim-ulation of controlled electric drives, " IEEE Trans. Ind. Appl., vol. 27, no. 6, pp. 1103–1110, Nov./Dec. 1991.
Sensitivity of SRM output on pole arc ratio
- R Arumugam
- J F Lindsay
- R Krishnan
sensitivity of srm output on pole arc ratio
- arumugam
design and implementation of linearizing and feedback transformation for switched reluctance motors
- taylor