Switched Reluctance Machine Research Articles

Design and Control of a Transverse Flux Linear Switched Reluctance Machine for Rail Transit Application

The design, optimization and control methods of a transverse flux Linear Switched Reluctance Motor (LSRM) for the rail transit application are introduced. Two structures of LSRMs, EI type and EE type, are compared and analyzed. The structure of EE type machine is optimized from the perspective of average electromagnetic thrust per unit mass through finite element calculations. The initial sizes of the motor are calculated according to the design theory of the rotary SRM. After obtaining the initial sizes, the sensitivities of the LSRM sizes are analyzed by the three-dimensional finite element calculation, and then the sizes such as the slot depth, the slot width and the tooth width of the motor are optimized. The hardware test platform is built, the electromagnetic characteristics of the prototype are tested, and the motor characteristics of the LSRM with different secondary materials are compared. The control method of the LSRM with position sensors is proposed, and then the sensorless control of the motor is also realized based on the pulse injection strategy. The experimental results verify the effectiveness of the design and control strategies.

An Intersection-Method-Based Current Controller for Switched Reluctance Machines With Robust Tracking Performance

Good current tracking is beneficial to the torque ripple suppression methods like current profiling techniques for the switched reluctance machines (SRMs). An intersection-method-based current controller for the SRM with robust tracking performance is proposed in this article. First, with the aid of the predicted current at the next sampling instant, the prestored reference current, and the flux-linkage information, the required duty cycle for the next control period under specific reference current is estimated through the intersection method. To compensate for the difference between the adopted flux-linkage model and the real ones inside the machine, a Lyapunov-based adaptive flux-linkage observer is presented. Hence, the heavy dependence issue on the accurate flux-linkage model for the current controller is resolved. With the above techniques, robust reference current tracking is achieved in a simple form and only one observer gain. Besides, a balanced switching scheme is presented to reduce the switching frequency requirement of the power transistors and evenly distribute the switching losses. Extensive experimental tests have been carried out on a four-phase 5.1-kW 8/6 SRM setup for the proposed method and conventional current control methods at different operation conditions. These testing results verified the effectiveness of the proposed method.

Numerical Investigation on Vibration Performance of an Improved Switched Reluctance Machine with Double Auxiliary Slots

Considerable vibration and acoustic noise limit the further application of Switched Reluctance Machine (SRM) due to its structural characteristics and working principle. An improved SRM model with double auxiliary slots (DAS) was proposed, in which the direction of the magnetic line of force was adjusted, and the radial magnetic density in the air gap was reduced by changing the local tooth profiles of the stator and the rotor. The effects of initial rotor position and turn-on angle and turn-off angle on radial Electromagnetic Force (EMF) and maximum torque were investigated. The results indicate the radial EMF and torque increase significantly with the advancement of the turn-on angle or the delay of the turn-off angle. In the orthogonal experimental design, initial rotor position, turn-on angle, and turn-off angle were taken as the factors, and the optimal set of parameters that minimized radial EMF was determined according to a greater output torque. In contrast to conventional SRM, the radial EMF of the SRM with DAS significantly reduces when the optimal set is applied.

High-Switching-Frequency SiC Power Converter for High-Speed Switched Reluctance Machine

This article reports design and testing of silicon carbide) devices-based three-phase asymmetric H-bridge converter capable of switching at 50 kHz and intended to drive high-speed switched reluctance machine. Electromagnetic designs of a 7.5-kW, 30 000-r/min and a 20-kW, 50 000-r/min Switched reluctance machine are presented. The 30 000-r/min machine is fabricated and characterized. A machine model is obtained from the measured characteristics. Based on the machine model, as well as drive operating variables and device data-sheet parameters, two methods are proposed for evaluating the losses in the power devices. The first method relies on machine model to obtain machine current and converter duty ratio, and thereby estimate the device losses. A second simplified method provides closed-form expressions for device losses. The proposed analytical expressions relate the machine characteristics such as inductance and saturation current with converter losses. The estimated loss is further used to predict device junction temperature. The power converter and device ratings are chosen so that the converter is suitable for both machines. The capacitor selection and sizing are discussed. Further, the power converter architecture and other subsystems of the converter are described. Test results are presented for the asymmetric H-bridge converter at 800 V dc bus voltage, 50 A of load current, and 50 kHz of switching frequency. Thermal image is presented for validation of estimated heat-sink temperature. The predicted heat-sink temperature is found to agree well with the measured temperature. The power converter is used to operate the 30 000-r/min machine at various speeds.

Optimization of Single Pulse Control based on Design of Experiments for Switched Reluctance Machines

Due to the robust structure of switched reluctance machines, high-speed operations are preferred in order to achieve higher power densities. Generally, at high speeds single pulse control is applied. However, its control parameter set is not unique. This paper proposes an algorithm based on design of experiments that allows the calculation of optimal control parameters for an operating area and the minimization of the total machine losses at the same time. The designed experiments are finite-element analyses (FEAs) considering both iron and copper losses. A Pareto search algorithm solves the proposed multi-objective optimization problem. The results for different response surfaces are compared regarding the errors in torque production and machine loss prediction. A reduced response surface based on 9 FE-runs shows a mean error of 1.9%, whereas the maximum error is 6.3% for the machine losses within the validation operating area.

A Magnetic Field Decoupling Double Stator Switched Reluctance Machine

This paper introduces a novel double stator switched reluctance machine (DSSRM). U-shaped stator blocks are used for both internal and external stators. Each stator tooth is wound with a central winding, and the polarities of the two stator teeth on each U stator block are opposite. Firstly, the working principle and the geometric design of the proposed DSSRM are given. The methods of reducing torque ripple from machine structure of the proposed DSSRM are illustrated. Then, this paper makes the comprehensive comparison between conventional DSSRM and proposed DSSRM by finite element method (FEM). The simulation results indicate that this proposed DSSRM has lower torque ripple and higher torque density than the conventional DSSRM. Finally, a prototype motor is manufactured and the simulation analysis is validated by the experimental results.

Artificial neural network vector controlled common high-side switch asymmetric converter fed switched reluctance motor drive

<p>The best alternative machine for synchronous and induction machine is switched reluctance machine for various applications. An artificial neural network (ANN) based vector controller is implemented for novel converter to drive switched reluctance motor (SRM) in this paper. To reduce the cost and simplified the controller an effective configuration of converter is proposed with only 4 pulse-withmodulation (PWM) based switches. The 6 pole stator and 4 pole rotor machine is considered in this paper to present results based on MATLAB. The ripples in torque are reduced by proposing vector controller by using novel configuration of converter. Generally SRM machines are having high ripples in torque, hence less number of switches will be feasible solution to drive the machine in order to reduce ripples. The proposed controller can also help to operate system with less ripples in torque since the controller having both torque and flux hysteresis controllers. The extensive results are presented on Simulink platform to validate the proposed method under both steady state as well as transient conditions.</p>

Principle, design and analysis of a novel axial flux switched reluctance machine with fully pitched winding structure

Principle, design and analysis of a novel axial flux switched reluctance machine with fully pitched winding structure

IMPROVEMENT OF THE DESIGN ALGORITHM OF SWITCHED-RELUCTANCE MACHINES

The issue of improving the technical and economic indicators of switched-reluctance machines at the stage of their design has a significant degree of relevance. This study is devoted to improving the optimization algorithm for designing electric machines of the valve-inductor type.
 Parametric, single-criteria optimization was subject to consideration. The task of designing a magnetic system of a switched-reluctance machine is to find the optimal combination of values of geometric parameters, at which the value of the objective function reaches an extremum. Within the framework of this work, optimization was considered by the criterion of the minimum pulsations of the electromagnetic moment at low rotational speeds.
 The stochastic method – the Monte-Carlo method – was used as the basis for making changes to improve the efficiency of the optimization algorithm. The essence of the changes is to apply a normal distribution of a random variable with decreasing variance and with a variable value of the mathematical expectation instead of using a uniform distribution.
 For this study, methods of mathematical modeling were used, namely the Monte-Carlo method and methods of probability theory. Calculations of the magnetic field of the switched-reluctance machine were performed using the FEMM 4.2 program based on the finite element method.
 Due to the changes made to the basic optimization algorithm, the effectiveness of such a criterion as the time to achieve the final result with a given calculation accuracy has become higher. The obtained data can be practically useful in the development of manufacturing technology for the object of optimization.

Design of a Low-Ripple Double-Modular-Stator Switched Reluctance Machine for Electric Vehicle Applications

To overcome the disadvantages of traditional switched reluctance machine (SRM) with moderate power/torque density and high torque ripple, this article proposes a novel double-stator SRM (DSSRM) with the inner and outer stators both adopting U-shaped segmental stator structure. By optimizing the polarity distribution of the inner and outer stator magnetic fields, the inner and outer stator magnetic fields are decoupled. Then, the relationships of torque ripple coefficient with the mechanical offset angles of the inner and outer rotor teeth are investigated. To optimize the mechanical offset angle and reduce the torque ripple of the motor, the initial design method is proposed, and five main parameters of the machine are optimized by the finite-element analysis. Then, the static magnetic characteristics and dynamic performance of this novel machine are simulated and analyzed. Finally, a 16/18/18/16 DSSRM is prototyped to validate the above simulation and theoretical analysis.

Experimental Vibration Studies on a Solid-Rotor Switched Reluctance Machine

Vibration characteristics of a solid-rotor switched reluctance machine (SRM) are measured in the static as well as dynamic conditions. A series of impulse hammer-based static measurements are carried out on the assembled machine. The impulse hammer tests identify the main resonant frequencies of the rotor assembly, bearing housing and enclosure. For the dynamic vibration tests, the SRM is run at different speeds using single-pulse control and current control. The measured currents are utilized to obtain the electromagnetic radial force on the stator through finite element analysis. The frequency components of the estimated radial force are observed in the vibration spectrum measured in the dynamic tests. The dynamic vibration spectrum also include the resonant frequencies of the SRM subassemblies. The natural frequencies of the rotor assembly are found to influence the vibration spectrum significantly. Harmonics of speed are the other significant components in the measured vibration spectrum at any given speed; the magnitudes of these components increase with rotor speed.

Performance Investigation of Switched Reluctance Motor Driven by Quasi-Z-Source Integrated Multiport Converter with Different Switching Algorithms

Switched reluctance machines (SRMs) have received increasing attention for their many potential uses, such as for wind power and electric vehicle (EV) drive systems. The Quasi-Z-source Integrated Multiport Converter (QZIMPC) was recently introduced to improve the reliability of the SRM driver through small capacitance values. It is not possible, however, to simultaneously energize and deenergize two SRM phases in QZIMPC. This phenomenon can significantly increase the commutation period which, in turn, degrades the performance of SRM; in addition, this causes high-voltage ripples on the converter’s capacitors. Two switching algorithms are introduced and applied in this paper, and their performance with SRM is investigated in terms of torque ripple and peak phase current. The algorithms are based on prioritizing the control command in the on-going and off-going phases to fulfill the required load torque, as well as to accelerate the commutation process where possible. This is achieved without the interference of high-level controllers, which include speed controllers and/or torque ripple minimization. Through the simulation results, a comparison between the two switching algorithms is presented to determine their potential to improve the SRM drive system’s performance.

Optimalisasi Pengereman Regeneratif dengan Perubahan Sudut Eksitasi pada Pulsa Tunggal

Most of the energy is wasted into heat energy due to conventional braking, so an optimal braking strategy is needed. A Regenerative braking utilizes the kinetic energy of the engine into electrical energy by changing the function of an electric machine into a generator. The regenerative braking system uses a Switched Reluctance Machine (SRM) which has several advantages; simple construction, does not require maintenance, and return energy to the battery. The method that can be used in the regenerative braking system of the SRM is the change of excitation angle to produce the maximum peak phase current. This study aims to optimize regenerative braking by changing the angle (θeks) using simple controls to produce energy that is greater than the battery voltage so that current may flow to the battery when braking occurs. The results of the analysis for method implementation were proven by testing the devices in the laboratory.  Based on the results of the tests, the exact angle was obtained, namely the value of θeks = 20º and the value of θkom = 170º with an initial speed of 1822 RPM, reduced into 1522 RPM by braking process, which could produce a peak current of 12,5 A and a current flowing to the battery was 5A.

Asymmetrical Rotor Skewing Optimization in Switched Reluctance Machines Using Differential Evolutionary Algorithm

Minimizing torque ripple in electrical machines for a given application is not a straightforward task, especially when the application imposes certain constraints. There are many techniques to improve torque ripple, either design-based or control-based. In this paper, a new geometry for switched reluctance machines based on rotor poles skewing is proposed to minimize torque ripple. This paper describes a methodology to design an asymmetrical skew rotor—switched reluctance machine using a multi-objective differential evolutionary algorithm. The main parameters of the optimization process are defined, as is the optimization methodology to obtain an improved design with less torque ripple than a conventional one. Moreover, the analytical formulas used in the optimization method, as well as the optimization technique, are deduced and explained in detail. The mathematical model used to simulate the electrical machine and the power converter are also described. Two-dimensional and three-dimensional finite element analyses were also conducted to assess whether 3D effects (end-effect and axial fringing field) affected the results. Finally, a particular case of a high-voltage direct current-controlled generator in the base of the More Electric Aircraft (MEA) concept or an energy storage system as an electrical machine was analyzed, and the results for the improved configuration were compared with those for the conventional one.

Experimental Determination of Equivalent Iron Loss Resistance for Prediction of Iron Losses in a Switched Reluctance Machine

Switched reluctance machine (SRM) has progressed as a suitable contender in the family of electrical machines for its high starting torque and better performance in different operating conditions. The need for accurate modeling of this machine is, therefore, dependent on the accurate determination of losses of which iron loss is exigent. This article aims to determine iron loss from the equivalent circuit parameters of the machine based on the input data tables that are directly obtained from the experiments carried out on an existing four-phase, bifilar wound SRM. The procedure and necessary steps for the loss separation method are well defined and supported by the theoretical and practical results. The experimental determination of the iron losses has been compared with the predicted results under the same operating conditions.

An Optimization-Based Initial Position Estimation Method for Switched Reluctance Machines

A new method to detect the initial rotor position of switched reluctance machine (SRM) is presented in this article. Unlike most conventional position estimation methods, the proposed method does not need any extra premeasurement and only the data with finite element method (FEM) are required. First, a linear regression model (LRM) is presented to describe the relationship between FEM and measured inductance characteristics. Then, to detect the position, the residual sum of squares of the proposed LRM is considered as an objective function, which is a convex function with rotor position. The rotor position can be estimated by minimizing the objective function with the golden-section search method. Finally, the accuracy of the proposed estimation algorithm is validated by the experimental results on a three-phase 12/8 pole SRM prototype. Compared with the existing position estimation methods, the proposed method has higher accuracy and less measurement effort. The proposed method can serve as a supplement to provide accurate initial position information for incremental position sensors.

Multi-Objective Optimization of Switched Reluctance Machine Design Using Jaya Algorithm (MO-Jaya)

The switched reluctance machine (SRM) design is different from the design of most of other machines. SRM has many design parameters that have non-linear relationships with the performance indices (i.e., average torque, efficiency, and so forth). Hence, it is difficult to design SRM using straight forward equations with iterative methods, which is common for other machines. Optimization techniques are used to overcome this challenge by searching for the best variables values within the search area. In this paper, the optimization of SRM design is achieved using multi-objective Jaya algorithm (MO-Jaya). In the Jaya algorithm, solutions are moved closer to the best solution and away from the worst solution. Hence, a good intensification of the search process is achieved. Moreover, the randomly changed parameters achieve good search diversity. In this paper, it is suggested to also randomly change best and worst solutions. Hence, better diversity is achieved, as indicated from results. The optimization with the MO-Jaya algorithm was made for 8/6 and 6/4 SRM. Objectives used are the average torque, efficiency, and iron weight. The results of MO-Jaya are compared with the results of the non-dominated sorting genetic algorithm (NSGA-II) for the same conditions and constraints. The optimization program is made in Lua programming language and executed by FEMM4.2 software. The results show the success of the approach to achieve better objective values, a broad search, and to introduce a variety of optimal solutions.

Segmented Rotor Mutually Coupled Switched Reluctance Machine for Low Torque Ripple Applications

Mutually coupled switched reluctance motors (MCSRMs) are alternatives in the family of reluctance machines that can overcome switched reluctance motor's (SRM's) system-level integration and control challenges by utilizing standard three-phase voltage source inverters. In this article, a novel segmented-rotor, fractional-slot, tooth-wound MCSRM with notched rotor design is presented, which has very low torque ripple compared to other machine types in the SRM family. The torque ripple is reduced to 3.6% without utilizing any current profiling techniques or torque sharing functions. The ripple minimization is achieved primarily through rotor segment shaping, which has a strong influence on stator flux densities, flux linkages, and torque harmonics. The design strategy, along with the optimization details, is presented for a 120 W, 12 slot-8 pole MCSRM. The designed MCSRM is prototyped for experimental verification and validation of the finite element analysis results and design methodology.

Unaligned inductance calculation using flux tube approach for rotor conducting screen‐based SRM

AbstractThis article investigates the effect of utilising rotor conducting screens within a switched reluctance machine (SRM). Conducting, non‐magnetic materials such as aluminium or copper are inserted into the interpole regions of the rotor. The effective unaligned inductance decreases, which increases the conversion area allowing the machine to develop more power. Predicting machine performance implies knowing the value of the unaligned inductance. A procedure for calculating the effective unaligned inductance for screened motors using the flux tube method is presented. Finite element analysis results establish the validity of the proposed calculation method. A detailed design procedure for screened SRM is presented.

Four-Quadrant Position Sensorless Operation of Switched Reluctance Machine for Electric Vehicles Over a Wide Speed Range

This article focuses on developing a four-quadrant position sensorless technique for switched reluctance machine (SRM) to meet the operating requirements of electric vehicles (EVs). The technique combines two different sensorless schemes and is implemented by the sensorless rules based on the rotor position partition. At startup and low speeds, the zones are identified based on the comparison of unsaturated inductances obtained by pulse current slope difference method, and the segmented Fourier series inductance model or the segmented linear inductance model is selected for position estimation according to the identified zones. At medium to high speeds, the zones are identified based on the comparison of flux linkage generated by excitation current and auxiliary chopping current. Only the segmented linear flux-linkage model is used for position estimation to reduce the computational burden of the processor. The transition methods are also presented to achieve seamless combination between the two sensorless schemes and the smooth transition from motoring to braking. This technique can deliver high-resolution rotor positions in full cycle and is implemented fast and easily. The experimental results on a 1.2-kW 12/8-pole SRM prototype verify the feasibility and correctness of the proposed sensorless control technique.