Three-phase Switched Reluctance Machine Research Articles

Modeling, Simulation and a Comparative study between a Single-phase Switched Reluctance Machine (6x6) and a Three-phase Switched Reluctance Machine

The comparative study of electric machines has been in vogue due to the growing demand for electromechanical converters with maximum possible efficiency. In this scene, the switched reluctance machines have proven to be competitive. Comparative studies between these machines and the already established induction machines can be easily found in the scientific literature, but studies on various configurations of the switched reluctance machines are not as widespread. This paper shows the modeling, simulation and presents a comparative study of two Switched Reluctance Machines to a single phase (6x6) and three phase (6x4). Aspects of construction, drive and efficiency are discussed in order to find advantages and disadvantages to each of these machines.

Stable Equilibrium Rotor Positions for Three-Phase Switched Reluctance Machine

In mobile applications such as eletric vehicles, weight and installation space are the primary limiting factors that affect the system efficiency and consequently the driving range. Reusing the machine windings of an electrical machine as inductors, e. g. in DC-DC converters for onboard chargers, saves weight and space. However, currents in the machine windings when operating as DC-DC converter can result in undesired torque ripple generated by the machine. Therefore, stable rotor positions of a switched reluctance machine have to be found to prevent it from rotating in DC-DC converter operation mode. In this study, stable rotor positions for a wide range of current distributions are determined, enabling flexibility in the choice of currents. A method to analyze such stable equilibrium positions for switched reluctance motors is presented. The proposed method is used to determine the stable positions that facilitate flexible current distribution between phases. Moreover, locus curves are calculated, simulated, and measured to illustrate and evaluate stable rotor positions for the various current distributions.

Design, simulation and optimisation of a novel low ripple outer-rotor switched reluctance machine for variable speed application

ABSTRACT Remarkable characteristics like simple structure, high starting torque, simple maintenance, good efficiency at all speeds and cost-effectiveness have made switched reluctance machines (SRMs) suitable candidates for electric cars, electric bicycles and variable speed applications (VSAs) such as wind turbines. In this paper, a three-phase Outer-Rotor SRM (ORSRM) with 6 stator poles and 10 rotor poles (6/10) for VSA has been investigated. Unlike conventional SRM structures such as 6/4 and 12/8, an SRM model with higher number of rotor poles can reduce torque ripple much more effective than conventional SRMs. First, the SRM design is done accurately, then, by changing some parameters, the sensitivity analysis is performed on torque ripple and average torque. Finally, the optimisation process on the geometry and structural dimensions of the SRM like rotor pole arc, stator pole arc, rotor yoke thickness, rotor pole height, rotor diameter and the number of turns per phase are executed to minimise the torque ripple and maximise the average torque via genetic algorithm (GA). The initial design, optimisation and performance of the proposed model are validated via a 2-D finite element method (FEM) technique by ANSYS-Maxwell.

Tork Salınımı Minimizasyonu İçin Modüler Yükseltici-Alçaltıcı Anahtarlamalı Relüktans Makinası Sürücü Sistemi

In this paper, a modular three-phase buck-boost switched reluctance machine (SRM) drive system is proposed. In this topology, the three-phase SRM drive is composed of three single-phase modules that are connected in parallel where each single-phase inverter module is formed with a bidirectional buck-boost DC/DC converter and a cascaded H-bridge inverter. The DC/DC converter generates the rectified form of the phase voltage and the H-bridge inverter alternates and controls the polarity of the output voltage. This structure allows one to adjust the phase voltages independently, which provides faster excitation and demagnetization for a wide range of operating conditions. Since the voltage is always regulated dynamically, the need for bulky DC-bus capacitors is eliminated; hence, the size and the cost of the drive system are reduced. To validate the superiority of the proposed system and compare it with the traditional one, a set of simulations are done in MATLAB®/Simulink®. Not only the torque ripple is reduced, but also a higher torque per ampere ratio is achieved with the proposed system.

Phase Current Reconstruction and Control of Three-Phase Switched Reluctance Machine With Modular Power Converter Using Single DC-Link Current Sensor

According to the modular power converter, a novel phase current reconstruction method using single dc-link current sensor is proposed for three-phase switched reluctance machine (SRM), and the control method is implemented with the reconstructed phase current as well. A highly integrated modular power converter is constructed by a three-phase full bridge and a dual switch module. The phase windings are in star-connection, and the bipolar phase currents are applied. Based on the special operating modes and single pulse width modulation signal injection, the dc-link current is decoupled and the phase current in both magnetization and demagnetization regions is reconstructed, which is very critical for the implementation of some advanced methods that require complete period phase current. The conventional control methods of the SRM, such as single-pulse voltage and hysteresis current control methods, are carried out under different operating conditions with both simulation and experiment to verify the effectiveness of the proposed method, and the reconstruction errors and performance influences are detailed analyzed as well.

Analysis and evaluation of modular E‐shaped stator switched reluctance machines employing segmented and conventional rotor topologies

Switched reluctance machines (SRMs) with modular or segmented structures normally have light weight, low cost, easily manufactured and improved fault-tolerance capability. In this study, two novel three-phase modular SRMs (MSRMs) with the same E-shaped stator modules and different rotor topologies, namely, segmented rotor and conventional rotor are evaluated and compared. The basic machine topologies and simplified magnetic equivalent circuit (MEC) are presented first. The static electromagnetic characteristics of two MSRMs such as flux distribution, phase flux linkage and inductance, electromagnetic torque, and so on, are computed and compared by three-dimensional finite-element analysis. Then, the dynamic performances including steady state and transient operations of two MSRM drives are evaluated and compared. The corresponding predictions and comparisons indicate that the segmented rotor topology has less iron consumption, higher torque density and power density and lower torque ripple, which is preferred for the three-phase MSRMs. Finally, two MSRM prototypes with segmented rotor and conventional rotor are manufactured and tested for experimental verification and comparison. The experimental results of static flux linkage, steady state and transient performances of two MSRM drives are presented and compared, which verify the analytical MEC model, finite element analysis and the corresponding predictions.

Control Performance Analysis and Improvement of a Modular Power Converter for Three-Phase SRM With Y-Connected Windings and Neutral Line

In this paper, the control performances of a modular power converter for a three-phase switched reluctance machine (SRM) are analyzed and improved. The converter is implemented by a dual and a six-pack IGBT module, and the phase windings of the SRM are Y-connected and bipolar excited. The performances of the existing control method for this converter are evaluated by simulation and compared with those for the traditional asymmetric half-bridge converter, and the drawbacks, such as big torque ripple and small average torque, are presented. With the new operating modes of phase branch, namely magnetization, freewheeling, and demagnetization, improved basic control methods are proposed, which can effectively enhance the performances, flexibility, and applicability of the converter. Furthermore, the direct instantaneous torque control, which can reduce the torque ripple, is realized with the converter as well. Several simulations and experiments under different working conditions are carried out to verify the performances of the improved control methods.

Stator/Rotor Pole Combinations and Winding Configurations of Variable Flux Reluctance Machines

In this paper, stator/rotor pole combinations, winding configurations, and electromagnetic performance of novel variable flux reluctance machines (VFRMs), which employ a doubly salient structure similar to switched reluctance machines (SRMs) but with stator-located dc field windings, are investigated. VFRMs with 12 stator poles are taken as examples to illustrate the method for determining the winding connections and winding factors. The back-electromotive force (EMF), self- and mutual inductances, cogging torque, static torque, torque ripple, and unbalanced magnetic force (UMF) are investigated by finite-element analyses. It is found that many stator/rotor pole combinations, i.e., 12/8 (which may be derived from the conventional three-phase SRM), 12/10, 12/11, 12/13, and 12/14, are feasible for the 12-stator-pole VFRMs. Among these pole number combinations, the 10- and 14-rotor-pole VFRMs can eliminate the inherent UMF in 6/5 and 6/7 VFRMs and exhibit more sinusoidal back-EMF waveforms and have higher torque density than an 8-rotor-pole VFRM, whereas the 11- and 13-rotor-pole VFRMs exhibit similar torque density as the 10- and 14-rotor-pole VFRMs, but with negligible cogging torque and torque ripple, albeit with UMF. Five prototype VFRMs with 12 stator poles and different rotor poles have been designed, manufactured, and tested to verify the analyses.

Position Estimation at Starting and Lower Speed in Three-Phase Switched Reluctance Machines Using Pulse Injection and Two Thresholds

The paper presents a method of accurate indirect position estimation for switched reluctance machines suitable for starting and continuous operation. The position estimation and control of the SRM is accomplished in terms of a few sectors within an electrical cycle. The sector of machine operation is obtained by comparing the injected current amplitude in an idle phase with two thresholds. Each sector is unique and identifies which phase has to be used for sensing and which phase has to be used for powering the SRM. A normalized inductance profile identified from the injected currents helps to develop an algorithm for the application of this method from low power to very high power machines with accurate and reliable estimation and control.

Design and Optimization of a Switched Reluctance Motor Driving a Compressor for a PEM Fuel-Cell System for Automotive Applications

This paper describes the design of a high-speed three-phase switched reluctance machine to drive a compressor for the air management of a fuel-cell system for automotive applications. The machine geometry is optimized by means of a finite-element method coupled to a genetic algorithm. The performance of the optimized machine is evaluated, taking into account the iron and air-friction losses. Some theoretical and numerical results are sustained by the measured ones in the same operating conditions.

Implementation of the Three-Phase Switched Reluctance Machine System for Motors and Generators

This paper presents two three-phase switched reluctance machine systems. One is the dual motors drive for the electric locomotive traction; the other is the variable-speed generator system for wind power applications. The principles of the switched reluctance machine system operated at four quadrants, the scheme of the symmetrical traction at quadrant I and quadrant III, and the scheme of the symmetrical regenerative braking control at quadrant II and quadrant IV, are given. The transient phase current analysis and the energy analysis of the switched reluctance machine system at the operational state of braking or generating are evaluated, and the rotor position and the peak value of the phase current at three different conditions are given. The closed-loop rotor speed control of the main motor, synchronization of the rotor speed, and balance distribution of loads between the main motor and the subordinate motor have been implemented by the fuzzy logic algorithm. The closed-loop output power control of the switched reluctance wind power generator system implemented by regulating the turn-on angle of the main switches with fuzzy logic algorithm and fixed turn-off angle of the main switches is also presented. The major components of the two prototypes are explained in detail. The experimental results of the dual 7.5-kW three-phase 6/4 structure switched reluctance motors (SRMs) parallel drive system prototype are included. It is shown that the maximum difference in the output torque of the two motors at the same given rotor speeds is within 10.00% and the maximum difference in the practical rotor speed of the two motors is within 5.00%. The tested results of three-phase 12/8 structure switched reluctance variable-speed wind power generator system show that the error of the closed-loop output power control is within 2.2%, while the rotor speed range is close to the ratio of 1:3 with the low rotor speed 405 r/min. The average dc line current of the power converter can be utilized as a feedback signal for the actual output torque of SRM drive or a feedback signal for the actual output power of switched reluctance generator system.

Design for torque ripple reduction of a three-phase switched-reluctance machine

This paper describes the design of a three-phase switched-reluctance machine in which there are overlaps between the phase current pulses in order to minimize the torque ripple, especially for high-speed operation. The machine dimensions are optimized by the finite-element method coupled to a cyclic process. Theoretical and experimental results obtained with the angle control strategy are presented.