Study on Magnetic Shielding for Performance Improvement of Axial-Field Dual-Rotor Segmented Switched Reluctance Machine

A category of permanent-magnet-shield(PM-shield)axial-field dual-rotor segmented switched reluctance machines(ADS-SRMs)are presented in this paper.These topologies are featured by using the magnetic material to shield the flux leakage in the stator and rotor parts.Besides,the deployed magnets weaken the magnetic saturation in the iron core,thus increasing the main flux.Hence,the torque-production capability can be increased effectively.All the PM-shield topologies are proposed and designed based on the magnetic equivalent circuit(MEC)model of ADS-SRM,which is the original design deploying no magnet.The features of all the PM-shield topologies are compared with the original design in terms of the magnetic field distributions,flux linkages,phase inductances,torque components,and followed by their motion-coupled analyses on the torque-production capabilities,copper losses,and efficiencies.Considering the cost reduction and the stable ferrite-magnet supply,an alternative proposal using the ferrite magnets is applied to the magnetic shielding.The magnet demagnetization analysis incorporated with the thermal behavior is performed for further verification of the motor performance.

Four-quadrant Force Control with Minimal Ripple for Linear Switched Reluctance Machines

Linear switch reluctance machine(LSRM)has been tried to act as an alternative generator for direct drive linear wave energy converter(WEC).Many researchers have proposed new topologies of LSRM to improve the power density,efficiency and reliability.However,the control methods for LSRM applied in direct drive WEC have been paid little attention,especially control methods considering the wave energy generator operating characteristics.In this paper,according to the generator control requirements of the direct drive WEC,force control algorithm for LSRM operating in four quadrants without a speed closed loop is put forward.The force ripple of LSRM is suppressed using force sharing function method.The four-quadrant control is easy to realize requiring only phase currents information.Simulation results validate the proposed method and indicate that LSRM is able to be used as the generator for direct drive WEC.

Evaluation of Switched-Reluctance Machine through Generalized Sizing Equations

With the evolution of converter fed machines (CFMs), it becomes important to evaluate the power potential of such machines of vastly different topologies with a variety of waveforms of back emf and current. It is based on the generalized sizing equations and permits the evaluation of the main dimensions with respect to the power of those machines. In this paper, a general approach is presented to extend the evaluation method of machine power density to the switched reluctance (SR) machine, and furthermore to compare the power production capability between the SR machine and the well known squirrel cage induction machine.

Analysis and Comparison of Power Electronic Converters for Conventional and Toroidal Switched Reluctance Machines

Different power electronic converter topologies are introduced in this paper for both Conventional Switched Reluctance Machine (CSRM) and Toroidal Switched Reluctance Machine (TSRM) drive systems. Their commutation, switch and diode currents, power losses, and efficiencies under over modulation operation are analyzed and compared for converter characteristics study, performance evaluation and topology selection for CSRM and TSRM drive systems. The switch and diode silicon volumes required for each CSRM and TSRM drives are also compared according to their corresponding currents at the equivalent machine torque versus speed operating points.

Torque Sharing Function Control of Switched Reluctance Machines with Reduced Current Sensors

This paper presents a Torque Sharing Function(TSF)control of Switched Reluctance Machines(SRMs)with different current sensor placements to reconstruct the phase currents.TSF requires precise phase current information to ensure accurate torque control.Two proposed methods with different chopping transistors or a new PWM implementation require four or two current sensors to replace the current sensors on each phase regardless of the phase number.For both approaches,the actual phase current can be easily extracted during the single phase conducting region.However,how to separate the incoming and outgoing phase current values during the commutation region is the difficult issue to deal with.In order to derive these two adjacent currents,the explanations and comparisons of two proposed methods are described.Their effectiveness is verified by experimental results on a four-phase 8/6 SRM.Finally,the approach with a new PWM implementation is selected,which requires only two current sensors for reducing the number of sensors.The control system can be more compact and cheaper.

Generic meminductive characteristics of switched reluctance machines

The meminductive system can be regarded as the generalization of the meminductor. This paper focuses on exploring the generic meminductive characteristics of the switched reluctance machine （SRM）. The dynamical equations of SRM sys- tems are derived and discussed in comparison with the typical constitutive relation equations of the meminductive system. Memory ability and pinched hysteresis loop （PHL） are taken as the indicative fingerprints to draw forth the theoretically comparative analysis. Based on the theoretical analysis, in addition to simulation and experimental confirmation, it can be concluded that from the viewpoint of circuit, SRM can be considered as a generic meminductive system.

Static Simulation of a 12/8 Switched Reluctance Machine (Application: Starter-Generator)

Because its high efficiency, its simple stator and rotor structures, the low cost and high reliability, speed operation combined with robust and low cost construction, the switched reluctance machines have represented. In recent years, an interesting alternative to other machine types has been chosen for traction applications especially starter-generator. Their rotors do not generate significant heat, resulting in easy cooling. Their unidirectional flux and current may generate lower core losses and require a simple converter design. Moreover, the switched reluctance machines are known for their high reliability and capability of operating in four quadrants for a variable speed drive. Despite those merits, switched reluctance machine has not been extensively used until recently because of its problems of torque ripples and noise. Additionally, researchers have faced many difficulties to build a SRM model because it is inherently multivariable. It has strong coupling and especially a high nonlinearity. In this paper, we deal with many modeling methods. Numerical, analytical and intelligent approaches are studied. The important aim in this research is to use static results from FEMM simulation as flux-linkage, co-energy, static torque to form a dynamic model of a switched reluctance machine used next as a starter-generator of a hybrid vehicle.

Design and Analysis of a Novel Rotor-Segmented Axial-Field Switched Reluctance Machine

As excitation strategy is influenced by the parity of phase number,and serious end effect is caused by full pitch windings adopted by the conventional rotor-segmented switched reluctance machine(RS-SRM),a novel rotor-segmented axial-field switched reluctance machine(RS-AFSRM),which adopts concentrated windings,is proposed in this paper,whose control strategy is independent of the parity of phase number.The stator of the proposed RS-AFSRM consists of inner and outer flux-conductive ring,excitation poles,and stator yoke,while the rotor consists of fan-shape cylinder-type segments.The structure and principle of the proposed machine is introduced through the magnetic circuit model of the machine.The fringing effect on air-gap field is considered.The simplified magnetic circuit considering the fringing effect is presented and the fringing effect coefficient is introduced.The design procedure considering the fringing effect through iterative modification is presented in this paper and is validated through 3D finite-element method(3D-FEM).Results show that both magnetic field distribution and operation are reasonable and satisfy the requirements.

Performance Evaluation and Comparison of Multi - Objective Optimization Algorithms for the Analytical Design of Switched Reluctance Machines

This paper systematically evaluates and compares three well-engineered and popular multi-objective optimization algorithms for the design of switched reluctance machines.The multi-physics and multi-objective nature of electric machine design problems are discussed,followed by benchmark studies comparing generic algorithms(GA),differential evolution(DE)algorithms and particle swarm optimizations(PSO)on a 6/4 switched reluctance machine design with seven independent variables and a strong nonlinear multi-objective Pareto front.To better quantify the quality of the Pareto fronts,five primary quality indicators are employed to serve as the algorithm testing metrics.The results show that the three algorithms have similar performances when the optimization employs only a small number of candidate designs or ultimately,a significant amount of candidate designs.However,DE tends to perform better in terms of convergence speed and the quality of Pareto front when a relatively modest amount of candidates are considered.

Electromagnetic Design of a Switched Reluctance Motor With Segmental Rotors and Full-pitch Windings

整距绕组分块转子开关磁阻电机具有高速运行时低风（油）阻和低铁心损耗等优点，特别适合用于航天航空驱动系统。根据整距绕组分块转子开关磁阻电机的基本工作原理，结合输出功率与平均转矩的关系，将绕组电流等效为方波，推导出了整距绕组分块转子开关磁阻电机的主体尺寸计算公式；基于电机定转子未对齐位置和对齐位置的电磁特性，以及整距绕组分块转子开关磁阻电机的电磁特点，确定了定、转子极弧系数选取的规则；同时分析了绕组匝数等主要尺寸的选取的规则；最后，基于上述方法优化设计了一台实验样机，并通过有限元仿真及实验验证了整距绕组分块转子开关磁阻电机的电磁设计方法的正确性。

Switched Reluctance Motor: Research Trends and Overview

There has been a growing interest in switched reluctance motor(SRM)ever since the development of thyristor in 1956.The most appealing feature of SRM which attracts researchers over these years is its simple structure that incorporates concentrated windings on the stator poles and plain laminations of ferromagnetic material as a rotor.Due to this attributes,advances are being made rapidly with the consideration that SRM can be used as an alternative to DC motors and permanent magnet motors.The objective of this paper is to present an overview of the recent developments and a prediction of possible future advancements in SR Drives.Brief history,importance,innovations in structure and control,along with practical application examples are all discussed here to give a more in-depth comprehension of the motor.

Improved Model of Radial Vibration in Switched Reluctance Motor Including Magnetic Saturation

This paper proposes an improved method for the prediction of radial vibration in switched reluctance motor(SRM)considering magnetic saturation.In this paper,the basic modeling principle is briefly introduced,it is based on the derivation that the peak acceleration is dependent on the product of phase current and current gradient idi/dt.However,the derivation may cause errors due to saturation effect.Thus in this paper,the discrete sample data are firstly acquired based on DC pulse measurement method,by which electromagnetic,torque and peak acceleration characteristics can all be acquired.Then the entire peak acceleration characteristics are obtained by improved Least Square Support Vector Machine(LSSVM).Based on the obtained static peak acceleration characteristics,the time-varied radial vibration model is established based on superposition of natural oscillations of dominant vibration modes.Finally,a simulation model is built up using MATLAB/Simulink.The good agreement between simulation and experiment shows that the proposed method for modeling is feasible and accurate,even under saturation.In addition,since LSSVM does not need any prior knowledge,it is much easier for modeling compared with other existing literatures.

Recent Development of Reluctance Machines with Different Winding Configurations,Excitation Methods,and Machine Structures

This paper reviews the performances of some newly developed reluctance machines with different winding configurations,excitation methods,stator and rotor structures,and slot/pole number combinations.Both the double layer conventional(DLC-),double layer mutually-coupled(DLMC),single layer conventional(SLC-),and single layer mutually-coupled(SLMC-),as well as fully-pitched(FP)winding configurations have been considered for both rectangular wave and sinewave excitations.Different conduction angles such as unipolar􀫚120°elec.,unipolar/bipolar􀫚180°elec.,bipolar􀫛240°elec.and bipolar􀫜360°elec.have been adopted and the most appropriate conduction angles have been obtained for the SRMs with different winding configurations.In addition,with appropriate conduction angles,the 12-slot/14-pole SRMs with modular stator structure is found to produce similar average torque,but lower torque ripple and iron loss when compared to non-modular 12-slot/8-pole SRMs.With sinewave excitation,the doubly salient synchronous reluctance machines with the DLMC winding can produce the highest average torque at high currents and achieve the highest peak efficiency as well.In order to compare with the conventional synchronous reluctance machines(SynRMs)having flux barriers inside the rotor,the appropriate rotor topologies to obtain the maximum average torque have been investigated for different winding configurations and slot/pole number combinations.Furthermore,some prototypes have been built with different winding configurations,stator structures,and slot/pole combinations to validate the predictions.

High Frequency Charging Techniques—Grid Connected Power Generation Using Switched Reluctance Generator

Power generation becomes the need of developed, developing and under developed countries to meet their increasing power requirements. When affordability increases their requirement of power increases, this happens when increased per capita consumption. The existing power scenario states that highest power is produced using firing of coals called thermal energy. A high efficiency Switched Reluctance Generator (SRG) based high frequency switching scheme to enhance the output for grid connectivity is designed, fabricated and evaluated. This proposed method generates the output for the low wind speed. It provides output at low speed because of multi-level DC-DC converter and storage system. It is an efficient solution for low wind power generation. The real time readings and results are discussed.

Design and Initial Testing of An Integrated Switched Reluctance Starter/Generator System for Unmanned Aerial Vehicle

According to specific performance requirements,an integrated switched reluctance starter/generator system,which can start the engine and supply electrical energy to the loads,is designed and manufactured for the unmanned aerial vehicle.Considering the required starting torque and speed range,the geometrical dimensions of the switched reluctance machine are calculated based on the output equation and further optimized with finite element analysis,and the flux-linkage,inductance and static torque characteristics are illustrated.To verify the performances of the designed system,detailed simulation with the model considering piston engine and experiment using the test bench are carried out.

Torque production mechanism of switched reluctance machines with field modulation principle

This paper aims to investigate the torque production mechanism and its improvement design in switched reluctance machines(SRMs) based on field modulation principle. Firstly, the analytical expressions of the air-gap magnetic field are derived from the perspective of DC-and AC-components, respectively. Meanwhile, different slot/pole combinations and winding arrangements are considered. Secondly, the torque productions are analyzed and evaluated with emphasis on the interaction between the DCand AC-components of air-gap fields. Thirdly, the 12-slot/8-pole and 12-slot/10-pole SRMs are established and studied by using the finite-element method. The effects of slot/pole combination and winding arrangement on the average torque production are clarified. Then, two new designs to improve the average torque are proposed. Finally, the prototype of the 12-slot/10-pole SRM is manufactured, and the experiments are carried out for validation.

基于特征位置区间电感阈值约束的SRM中高速无位置传感器容错控制

针对开通角提前、磁路饱和造成的位置估算扰动问题,该文提出一种基于特征位置区间电感阈值约束的开关磁阻电机中高速无位置传感器容错控制方案,有效提高定转子对齐位置估计的准确性与可靠性。考虑到电流水平较低时难以提取对齐位置信息,在辅助电流斩波的基础上提出自适应启停控制策略,既保证控制系统在电机轻载、参考转速突降时能够准确完成特征位置的估计,又避免了产生不必要的开关损耗及负转矩。仿真和实验结果验证了该文所提无位置控制方案在电机轻载、重载、参考转速及负载突变等多种工况下的有效性。

Quantitative Comparison of Electromagnetic Performance of Electrical Machines for HEVs/EVs

In this paper,various types of sinusoidal-fed electrical machines,i.e.induction machines(IMs),permanent magnet(PM)machines,synchronous reluctance machines,variable flux machines,wound field machines,are comprehensively reviewed in terms of basic features,merits and demerits,and compared for HEV/EV traction applications.Their latest developments are highlighted while their electromagnetic performance are quantitatively compared based on the same specification as the Prius 2010 interior PM(IPM)machine,including the torque/power-speed characteristics,power factor,efficiency map,and drive cycle based overall efficiency.It is found that PM-assisted synchronous reluctance machines are the most promising alternatives to IPM machines with lower cost and potentially higher overall efficiency.Although IMs are cheaper and have better overload capability,they exhibit lower efficiency and power factor.Other electrical machines,such as synchronous reluctance machines,wound field machines,as well as many other newly developed machines,are currently less attractive due to lower torque density and efficiency.

On the Algorithms of Adaptive Neural Network-Based Speed Control of Switched Reluctance Machines

<Abstract>A switched reluctance machine(SRM)drive is a time-varying,strongly nonlinear system.High performance control can no longer be achieved by using linear techniques.This paper describes the back-propagation (BP)neural network-based proportional-integral-derivative(PID)speed control of the SRM.It’s the interest of this paper to explore the utilization of the prior empirical knowledge as guidance in the initializing and training of the neural networks.The purpose is to make the networks less sensitive on the initial weights.Two modified algorithms are presented and simulation experiments show some interesting findings about their control effects and their corresponding sensitivity on the initial weights of the networks.

Analysis of vibration reduction level in an 8/6 switched reluctance machine by active vibration cancellation

This paper proposes an analytical model for predicting the maximum vibration reduction level in a four-phase 8/6 switched reluctance machine(SRM) by employing active vibration cancellation(AVC),one of the most effective and convenient methods for reducing the vibration and acoustic noise produced by SRMs.Based on the proposed method,the factors that influence the vibration reduction level are analyzed in detail.The relationships between vibration and noise reduction levels at resonance frequency and rotor speed are presented.Moreover,it is shown that a large damping factor will lead to smaller vibration reduction level with AVC while,in contrast,a large resonance frequency will increase the vibration reduction level.Both finite element analyses and experiments were carried out on a prototype 8/6 SRM to validate the proposed method.