Switched Reluctance Motor Research Articles

Torque Control Method for Switched Reluctance Motor based on Equivalent Inductance of Magnetic Co-energy

This paper proposes a torque ripple suppression method for a switched reluctance motor (SRM) with only measurable parameters. A large third-order torque ripple is generated via a conventional method with constant dq0-axis current, which is the dq-axis current and zero-phase current converted from the three-phase current of the SRM. The proposed method derives the zero-phase current with the third-order harmonic to suppress the torque ripple from a torque equation by considering the spatial harmonics of the inductance profile up to the fourth order and torque/current ratio in the entire region. Additionally, the average torque equation is derived from the inductance expressing the magnetic co-energy at the magnetic saturation. Consequently, the experimental results confirm that the torque ripple is reduced by 86.5% in the linear region and by 83.2% in the magnetic saturation region compared to the conventional method with the constant dq0-axis current. Finally, the derived average torque equation agrees with the experimental results, including the error of 5.2%.

An Online Torque Sharing Function Method Involving Current Dynamics for Switched Reluctance Motor Drives

This article proposes an online torque sharing function (TSF) method for torque ripple reduction in switched reluctance machines (SRMs). The proposed TSF takes the current dynamics and induced electromotive force (EMF) into account by establishing a new online current profile generation technique. First, a primary phase current reference derived from the torque reference is applied to the SRM. Then, the decaying phase current after the turn-off angle is sampled and it is used to update the current reference. A new online optimization strategy is performed to shape the current reference during the operation of the machine. Due to the proposed current profile generation technique, the optimization process is decoupled to independently minimize the torque ripple by optimizing the turn-on angle and minimizing copper losses by optimizing the turn-off angle. Compared to the conventional TSFs and existing optimization-based TSFs, the proposed TSF achieves accurate torque control, improved torque–speed capability, reduced torque ripple, and better current tracking performance. Simulations and experiments are performed on a three-phase 12/8 SRM under various operating conditions to validate the proposed online TSF method.

Evaluation of DC Excitation of External-Rotor-Segment-Type SRM for Power Generation

We evaluate an external segment-type switched reluctance motor (ESSRM) generator via simulations and experiments on an actual ESSRM. In the simulation, the shape of ESSRM was optimized using a genetic algorithm with two shape sizes varied as parameters. As a result of calculating 480 different shapes, it is found that the model that optimized by the genetic algorithm has a 1.45% higher power generation efficiency of 95.08% and a 634W higher generated power of 2,896W than the model optimized using a single parameter. To prototype a small SRM for evaluating the validity of the simulation model, the ESSR simulation model is similarly miniaturized. We developed a small model of ESSRM and conducted power generation experiments. In the ESSRM, the maximum power generation efficiency was measured as 62.13% when the generated power was 81.20W. As a result of comparing the simulation results with the experimental results by changing the number of segments, consistently the power generation efficiency was consistently highest when the number of segments was five in both experiments and simulations. The results confirm the validity of the simulation model.

Wireless Power Transmission-Based In-Wheel Switched Reluctance Motor Drive System With an x-Type Converter

This paper proposes a wireless power transmission (WPT)-based in-wheel switched reluctance motor (IWSRM) drive system, which uses an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x-</i> type converter at the motor side with charging function. In this system, a single frequency WPT subsystem with one transmitter coil and one receiver coil is used to completely isolate the DC power side from the motor side, and realize a transmission voltage gain of 1 by incorporating the symmetrical LCC-S network, which has the advantage of constant voltage gain when load changes. Be different from asymmetric half-bridge (AHB) converter, at the motor side an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x-</i> type converter with minimum number of active power switches is employed to connect the WPT subsystem, in which one power switch and one diode are used for each phase with independent control. The number of power active devices are reduced by half compared to AHB converter. Two freewheeling modes are analyzed for the drive system: the resistance freewheeling mode and the battery charging freewheeling mode. An experimental setup for a WPT-based three-phase 18/24-pole IWSRM system was built and tested. The simulation and experiment results of the system under two freewheeling modes are presented to validate the analysis and effectiveness of the system. The DC-to-DC efficiency is achieved over 96% with 100 mm air gap and the system efficiency is achieved up to 82% with the battery charging freewheeling mode.

Low-Cost Realization of Feature Position Estimation Scheme for Switched Reluctance Motor

This letter proposes a low-cost feature position estimation scheme for singly excited SRM without using lookup tables. This scheme uses the particular flux linkage versus current curve, corresponding to the commutation angle, to generate a flux-linkage reference. Phase commutation is executed at the instant when the online estimated flux linkage reaches this reference threshold. So, this letter, initially, proposes a novel analytical method to compute the reference flux linkage from phase currents. Then, a new approach is presented that maps the individual measured phase currents and estimated flux linkages into corresponding unified signals to reduce the computational burden. Thereafter, the mutual coupling among phases is shown as a cause of serious error in the thresholding operation, and a design criterion to avoid this error is derived. Performance of the proposed sensorless scheme is experimentally validated on a 1 kW, 3000 r/min, 6/4 SRM-based laboratory prototype.

Electromagnetic Modeling and Investigation for Bearingless Switched Reluctance Motor Considering Magnetic Saturation

For 12/4 bearingless switched reluctance motors (BSRMs), the levitation forces are generated in the maximum-inductance flat region of each phase. The magnetic saturation can be reached with the increase in ampere turns. In this paper, the mathematical model considering magnetic saturation is proposed to overcome the problem associated with the nonlinear characteristic. Three regions are divided in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$B$</tex-math></inline-formula> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$H$</tex-math></inline-formula> loop according to the change of relative permeability with magnetic field intensity. In addition, the single-valued expression between the flux density and the magnetic flux density is defined. The different parameters, i.e., air gaps, lamination, and rotor angle, influencing the performance of BSRM are analyzed. In the control process, the lookup tables (LUTs) of the electromagnetic forces based on the mathematical model are obtained. Finally, the experimental results for the 12/4 BSRM verify the feasibility of the proposed model.

Economic and Performance Evaluation of Direct Coupled Motors for Electric Vehicles

Because of constant increase in demand on Electric Vehicles (EVs) and Hybrid Electric Vehicles (HEVs) observed during the last decade, electrical machines manufacturers are confronted with technical and economic constraints, such as cost, weight, torque density, and torque ripple. To satisfy these requirements, this study proposes and applies a method for optimal choosing of competitive motors dedicated to the automotive applications. First a literature review is presented on the electric motors applied to drive systems including Synchronous Reluctance Motors with flux barriers (SynRM), Permanent Magnet Synchronous Motors (PMSM), Induction Motors (IM) and Switched Reluctance Motors (SRM). Subsequently, several candidates of machines that comfortably handle the exigencies of the propulsion system were analysed. Thus, the result of analyses leads to deal with PMSM and SynRM candidate machines regrading to the selected criteria and their numerical electromagnetic models are proposed and simulated using two-dimensional finite element analysis in order to compare their performance under both technical and economic requirements of the road vehicles market. The results of this study indicate that the SynRM is the optimal choice for challenging moderate-cost, high-performance of EVs and HEVs drives.

Multi-objective optimization design of novel tubular switched reluctance motor

PurposeThe purpose of this paper is to achieve the multi-objective optimization design of novel tubular switched reluctance motor (TSRM).Design/methodology/approachFirst, the structure and initial dimensions of TSRM are obtained based on design criteria and requirements. Second, the sensitivity analysis rules, process and results of TSRM are performed. Third, three optimization objectives are determined by the average electromagnetic force, smoothing coefficient and copper loss ratio. The analytic hierarchy process-entropy method-a technique for order preference by similarity to an ideal solution-grey relation analysis comprehensive evaluation algorithm is used to optimize TSRM. Finally, a prototype is manufactured, a hardware platform is built and static and dynamic experimental validations are carried out.FindingsThe sensitivity analysis reveals that parameters significantly impact the performance of TSRM. The results of multi-objective optimization show that the average electromagnetic force and smoothing coefficient after optimization are better than before, and the copper loss ratio reduces slightly. The experimental and simulated results of TSRM are consistent, which verifies the accuracy of TSRM.Research limitations/implicationsIn this paper, only three optimization objectives are selected in the multi-objective optimization process. To improve the performance of TSRM, the heating characteristics, such as iron loss, can be considered as the optimization objective for a more comprehensive analysis of TSRM performance.Originality/valueA novel motor structure is designed, combining the advantages of the TSRM and the linear motor. The established sensitivity analysis rules are scientific and suitable for the effects of various parameters on motor performance. The proposed multi-objective optimization algorithm is a comprehensive evaluation algorithm. It considers subjective weight and objective weight and fully uses the original data and the relational degree between the optimization objectives.

Mechanism analysis and optimum control of negative airgap eccentricity effect for in-wheel switched reluctance motor driving system

In this paper, the generation mechanism of the negative airgap eccentricity effect for the in-wheel switched reluctance motor (SRM) driving system is analyzed. An independent current chopping control strategy is proposed to achieve optimum control between the response characteristic of the in-wheel motor driving system and the dynamic performance of electric vehicle (EV). Firstly, the electromagnetic characteristic of the studied SRM under airgap eccentricity is studied based on electromagnetic coupling model and circuit driving equation, and the radial electromagnetic force under different airgap eccentricity is verified by adopting the built experiment device. Then, combined with the excitation characteristics of the radial electromagnetic force, the negative dynamic effect of the in-wheel motor driving system is analyzed in the time–frequency domain. Finally, an independent current chopping control strategy for the in-wheel SRM driving system based on vehicle vibration feedback is proposed. The controller parameters including the turn-off angle and chopping current threshold are optimized by data interpolation. Results show that the proposed control strategy can achieve the optimum control between the response characteristics of the in-wheel motor driving system and the vehicle dynamic performance, especially to suppress the vehicle sprung mass acceleration and tire bounce while starting EV.

Thermal Analysis of Switched Reluctance Motor Based on RMXprt/Motor-CAD

Switched reluctance motor (SRM) is an electric motor works based on the reluctance torque produced due to the variation of the rotor pole position with respect to stator poles. This paper adopts a thermal analysis on a 4-phase, 8/6 pole, 550W, SRM. Lumped parameters thermal network method(LPTN) is used in this analysis based on a combination of RMXprt/Motor-CAD software, in two- dimensional(2D), steady-state, with different cooling methods, and with different loading conditions. Motor losses like core losses, copper losses, and mechanical losses are regarded as the heat sources in SRM which are calculated by RMXprt software. The thermal analysis achieved by Motor-CAD includes displaying the temperature distribution on different motor parts like stator winding, stator poles, stator yoke, rotor poles, rotor yoke, shaft, covers, and housing. The analysis results showed the increasing temperature distribution on different motor parts with increasing motor loading conditions. Also, this temperature distribution is recorded using three different cooling methods. The comprehensive thermal analysis applied in this work will assist the motor designer in choosing a better motor thermal design without needing to produce and test costly prototype motors.

Sizing of a Traction Switched Reluctance Motor for an Electric Refuse-Collecting Vehicle Application

Refuse-collecting vehicles are significant polluters due to their expected drive cycles involving frequent stops and long idle periods. Electric refuse-collecting vehicles, still in their infancy, promise to address this through the replacement of internal combustion engines with batteries and electric traction motors. Today, typical motors for these vehicles involve heavy use of rare earth permanent magnets, which are subject to high price volatility, environmentally damaging mining practices, and occupational health hazards associated with refinement. The switched reluctance motor, which makes use of no permanent magnets, is a suitable substitute. This type of motor technology offers several advantages such as simple and robust construction, the ability to operate at high speeds and high temperature conditions, fault tolerance capability, and lower production costs in comparison with other technologies. This paper focuses on the design process of a switched reluctance motor for a battery electric refuse-collecting vehicle. The designed motor has a 36/24 outer rotor configuration, and its electrical and mechanical characteristics are based on the commercial traction motor TM4 SUMO HD HV3500-9P. The performance of the motor is evaluated using simulation tools such as JMAG and MATLAB/Simulink.

Parametric Modeling and Optimization of Switched Reluctance Motor for EV

To meet the high- performance requirements of new energy vehicle drive, the optimization design of 8/6 Switched Reluctance Motor is realized based on finite element parametric modeling of the motor. Firstly, the initial design of motor structure parameters is carried out based on the mathematical model of Switched Reluctance Motor, and the simulation model of the motor is built using RMxprt platform, and the debugging of the characteristics of the wide speed range of the motor is finished. Then, the parametric finite element model of the motor is generated, and the stator and rotor pole arc coefficients of the motor are selected as the optimization variables, and the multi-objective compromise optimization of the torque characteristics and efficiency of the motor is carried out by using the Quasi-Newton method weighting method. Finally, the magnetic field distribution, torque characteristics, efficiency and speed range characteristics before and after optimization are compared, proving that the optimized Switch Reluctance Motor can achieve multi-objective performance optimization. The motor designed by this modeling optimization method can improve the requirements of vehicle driving better.

Improved Torque Ripple of Switched Reluctance Motors using Sliding Mode Control for Electric Vehicles

This study describes the direct torque control-DTC approach, based on the Sliding Mode Control (SMC) technology with chattering reduction, for reducing the torque ripple of the Switched Reluctance Motor (SRM). The SRM torque control loop has been given the SMC treatment to account for the low-frequency fluctuations in the torque output. To maintain a consistent motor speed, the sliding mode controller modifies the value of the reference current. The findings demonstrate that the constant sliding mode controller is superior to PI controllers at lowering the motor's torque ripple, compensating for its nonlinear torque characteristics, and rendering the drive insensitive to parameter changes. MATLAB/SIMULINK simulation has been used to show how well this SMC performs. The performance of the proposed SMC method has been demonstrated by simulation in MATLAB/SIMULINK with a three-phase 8/6 pole, and a 2kW SRM.

Analysis of linear permanent magnet switched reluctance motors with modular and segmental movers

AbstractHere, the authors propose two new Permanent Magnet (PM) embedded linear switched reluctance motors; one is a modular linear hybrid reluctance motor (MLHRM), and the other one is a segmental linear hybrid reluctance motor (SLHRM). Both structures employ PMs between the side teeth of the modules/segments. The main contribution of the PMs is to increase the air‐gap flux density, which results in an enhanced thrust, and decrease the magnetic saturation in iron parts. The magnetic equivalent circuit model is used to demonstrate the positive effect of inserting PMs in the MLHRM and SLHRM compared to their PMless counterparts. The optimal pole number and design procedure are illustrated. The simulation results are obtained in terms of static thrust, flux linkage, flux density distributions, and steady‐state current and thrust. The results show that the proposed MLHRM and SLHRM offer a higher thrust and lower current compared to their PMless form. Also, the PMs decrease the root mean square (RMS) current under the steady‐state performance of the motors, in which a higher thrust is produced with a lower RMS current. Finally, the MLHRM and SLHRM are fabricated and the test results are obtained and compared with the simulations, which illustrate a satisfactory agreement.

Analysis and Design Considerations of a Buck-Boost Energy Recovery-Based Power Converter for SRM Drive

This article presents the development of a dynamic model and a design approach for the recently proposed buck-boost energy recovery circuit (BBERC) based power converter for a switched reluctance motor (SRM). The advantage of an increased demagnetization voltage in reducing the commutation torque ripple is analyzed using analytical and simulation-based studies. Though there have been several studies on the steady state behavior of the energy recovery stage in the literature, the dynamics of the same have never been investigated. An equation-based small signal model to describe the dynamic behavior of the energy recovery stage is proposed, which can be used to estimate the overshoots and oscillations in the inductor current and capacitor voltage during the dynamics. This article also evaluates the effects of discontinuous conduction mode (DCM) of operation of the BBERC on the drive performance, which has also not been addressed in the prior art. Furthermore, a method for the design of the energy recovery stage considering the continuous conduction of the energy recovery inductor is proposed. Additionally, the advantages of BBERC are reemphasized by comparing it with other energy recovery-based topologies such as energy efficient C-dump converter (EECDC). The analyses presented in this article are validated with experiments and simulations.

Interactive multi-model fault diagnosis method of switched reluctance motor based on low delay anti-interference.

Given fault false alarm and fault control failure caused by the decrease of fault identification accuracy and fault delay of Switched Reluctance Motor (SRM) power converter in complex working conditions, a method based on the Interactive Multi-Model (IMM) algorithm was proposed in this paper. Besides, the corresponding equivalent circuit models were established according to the different working states of the SRM power converter. The Kalman filter was employed to estimate the state of the model, and the fault detection and location were realized depending on the residual signal. Additionally, a transition probability correction function of the IMM was constructed using the difference of the n-th order to suppress the influence of external disturbance on the fault diagnosis accuracy. Concurrently, a model jump threshold was introduced to reduce delay when the matched model was switched, so as to realize the rapid separation of faults and effective fault control. The simulation and experiment results demonstrate that the IMM algorithm based on low delay anti-interference can effectively reduce the influence of complex working conditions, improve the anti-interference ability of SRM power converter fault diagnosis, and identify fault information accurately and quickly.

Torque Ripple Suppression of Switched Reluctance Motor with Reference Torque Online Correction

High torque ripple dramatically affects the switched reluctance motor (SRM) application. To reduce the torque ripple, a reference torque neural network (RTNN) is proposed to adjust the reference torque online. Firstly, the RTNN is built on the torque sharing function (TSF) method. Furthermore, the RTNN is designed as a single-input and -output network. As the periodic relationship between the torque ripple and the rotor angle, the rotor angle constitutes the central node parameter of the implicit function in RTNN. Therefore, one-step adjustment of the RTNN can perform well at restraining reference torque. Lastly, the torque error is used to adjust the parameters of RTNN to reduce the torque ripple. In the MATLAB environment, through the simulation comparison with fuzzy torque and PD current compensation method, the effectiveness of RTNN at torque ripple suppression is proven with different loads and speeds.

Design and analysis of a new bearingless switched reluctance motor

A bearingless switched motor with permanent magnets in the stator yoke (BSRM-PMSY) with two sets of windings on each stator tooth pole is studied. The current in one set of windings mainly controls the motor torque, and rotor suspension can be realised by adjusting the current in the other set of windings. Each stator module unit of the motor is composed of a permanent magnet and two U-shaped iron cores. Finally, a BSRM-PMSY finite element simulation model is established to explore the static characteristics of the motor, including magnetic field distribution, permanent magnet flux linkage and harmonic analysis, back electromotive force (EMF) and harmonic analysis, suspension performance, and so on. The analysis of the simulated results lays a foundation for the establishment of a BSRM-PMSY mathematical model and control system.

Vibration Analysis of Switched Reluctance Motor Based on Multi-objective Genetic Algorithm

Vibration Analysis of Switched Reluctance Motor Based on Multi-objective Genetic Algorithm

Analysis of Skewing Effects on Radial Force for Different Topologies of Switched Reluctance Machines: 6/4 SRM, 8/6 SRM, and 12/8 SRM

Reducing vibration and noise in electrical machines for a given application is not an easy task, especially when the application imposes some restrictions. There are many techniques for reducing vibration based on design or on control. Switched reluctance motors (SRMs) have a double-saliency structure, which results in a radial pulsation force. Consequently, they cause vibration and acoustic noise. This paper investigates the correlation between the radial force and the skew angle of the stator and/or rotor circuits. The analysis is computed from two-dimensional (2D) transient magnetic finite-element analysis (FEA) of three machine topologies, namely the 12/8 three-phase SRM, the 6/4 three-phase SRM and the 8/6 four-phase SRM. Compared to SRM, these topologies have the same basic dimensions (stator outer diameter, rotor outer diameter, and length) and operate in the same magnetic circuit saturation. The flux linkage and torque characteristics of the different motors are presented. The radial force distributed on the stator yoke under various skewing angles is studied extensively by FEA for the three machines. It is also demonstrated the effect of skewing angles in the reduction of radial force without any reduction in torque production.