Radial force calculation and acoustic noise prediction in switched reluctance machines

This paper presents an analytical method for calculating the radial force and predicting the acoustic noise in switched reluctance machines (SRMs). The main source of acoustic noise in an SRM is the radial magnetic force inducing resonant vibration with circumferential mode shapes of the stator. An analytical relationship between radial force and radial vibration is determined, which can be used to predict the noise power level at the frequency of operation. The vibration and sound are functions of machine dimensions, material properties, and rotational speed. The knowledge of the circumferential mode shapes of vibration, the natural mode frequencies of the stator, and the frequency spectrum of the radial magnetic force can be effectively utilized to design SRMs with minimal noise through geometrical design variations. The effect of the number of stator and rotor poles on acoustic noise can also be analyzed with the model presented in this paper. Magnetodynamic simulation by finite-element analysis software has also been carried out to verify the calculation of radial force using the proposed analytical model.     

Impact of stator windings and end-bells on resonant frequencies and mode shapes of switched reluctance motors

One of the main drawbacks of switched reluctance motors (SRMs) is vibration and acoustic noise, which limits their application. An accurate predication of the modal vibration frequencies of the SRM stator is essential in order to design a low-vibration motor and operate it quietly. Electronic techniques for noise reduction also depend on knowledge of the resonant frequencies, which depend on the mechanical structure surrounding the laminations. This paper examines the effects of the stator windings and end-bells on stator modal vibration frequencies. The error in the calculation of the resonant frequencies can be up to 20% if the influence of end-bells is neglected. The numerical computations of the stator mode shapes and resonant frequencies are validated with experimental results.     

Design Method for Improving Motor Efficiency of Switched Reluctance Motor

The motor efficiencies of switched reluctance motors (SRMs) are inferior to those of permanent magnet synchronous motors. This paper describes a design procedure for an SRM to obtain a higher motor efficiency. The first step in the design procedure makes clear the principle for improving the motor efficiency. The cross‐sectional and axial shapes of the rotor and stator cores are designed by magnetic field analysis with the two‐dimensional (2D) and 3D finite element method. A high‐efficiency SRM with 12 stator poles and eight rotor poles is designed. The designed SRM was produced experimentally, and was tested to verify its performance. The motor efficiency was improved in comparison to the standard SRM with six stator poles and four rotor poles.     

开关型磁阻电动机固有频率解析计算

运用机电类比法分析了开关型磁阻电动机(SRM)定子振动特性，针对传统解析计算方法仅将定子凸极和绕组以附加质量归入磁轭、但不计其刚度影响的局限性，提出了基于定子凸极归算算法的SRM固有频率解析计算方法。两台典型结构的SRM样机解析计算和二维有限元分析、模态实验结果表明，采取不计定子绕组影响而等效计及定子凸极对磁轭质量和刚度影响的机械阻抗法是一种对SRM定子振动特性进行解析分析的工程实用方法。     

Novel Two-Phase Switched Reluctance Machine Using Common-Pole E-Core Structure: Concept, Analysis, and Experimental Verification

A novel two-phase switched reluctance machine (SRM) with a stator composed of E-core structure having minimum stator core iron is proposed. The E-core stator has three poles with two poles at the ends having windings and a center pole containing no copper windings. The center stator pole in the E-core is shared by both phases during operation. The air gap around the common stator pole has constant and minimum reluctance irrespective of rotor position by its unique design, and the two remaining stator poles at the ends experience variable reluctance with respect to rotor position. The stator is constructed with two independent and physically separate E-cores, and the rotor is composed of ten poles. Other pole combinations are possible. Phase excitation in the novel SRM gives short flux paths, hence reducing the magnetomotive force required to drive the machine, resulting in significant reduction of copper wire and core losses compared to existing two-phase SRMs with flux paths that traverse the entire stator back iron. The concept and principle of operation of this novel SRM and its comparison to existing two-phase SRMs are detailed in this paper. Comparison between finite-element simulations and magnetic equivalent circuit (MEC) analysis for inductance are made and compared to experimentally measured characteristics. Furthermore, comparisons between a conventional two-phase SRM and the novel SRM are made in terms of its weight and output torque. Manufacturability and cost savings of the unique SRM structure are presented. It is shown that the E-core SRM using common stator pole has 50% less iron in the magnetic path compared to a conventional two-phase SRM.      

Vibration modes and acoustic noise in a four-phase switchedreluctance motor

Acoustic noise in the switched reluctance motor (SRM) is caused primarily by the deformation of the stator lamination stack. Acoustic noise is most severe when the periodic excitation of the SRM phases excites a natural vibration mode of the stack. The natural vibration modes and frequencies of a four-phase, 8/6 SRM are examined. Structural finite element analysis is used to compute the natural modes and frequencies. Impulse tests on the stator stack verify the calculations and show which modes are excited. Heuristic arguments are developed to predict the operating conditions that will excite the natural modes. Measurement of vibration while the machine is under load shows which operating conditions excite the natural modes and verifies the predictions. An approximate formula is derived to predict the frequency of the fundamental vibration mode in terms of lamination dimensions and material properties. The formula is validated by comparison with finite element calculations for several laminations, and hence is shown to be useful in design trade-off studies     

New pole tip shapes mitigating torque ripple in short pitched and fully pitched switched reluctance motors

High torque ripple is one of the major disadvantages of switched reluctance motor (SRM). Although there are several publications in the literature addressing the full or partial solution to the problem for conventional SRM, no publication exists for the torque ripple reduction of recently emerging fully pitched SRM. This paper deals with finding best dimension set for a particular stator and rotor pole tip shape aiming to reduce torque ripple in both short pitched and fully pitched SRMs. Five new stator and rotor pole tip structures have been investigated and compared with conventional pole tip. Analyses have been performed with the finite element (FE) models of 6/43-phase short pitched and fully pitched SRM with unipolar excitation. With the proposed pole tips, torque ripple is reduced by 24.1% in short pitched SRM for 10 A phase current and by 22.6% in fully pitched SRM for 5.59 A phase current.     

抑制开关磁阻电机振动的结构设计研究

开关磁阻电机(SRM)应用于众多领域,但是本身的结构使其比其他传统电机有更大的振动和噪声,因此抑制SRM振动仍是研究的热门领域。为了抑制电机的振动,设计了一种新型的电机结构,即在转子两侧开孔,并在此基础上对定子齿顶开槽。以一台7.5 kW、1 500 r/min、12/8极SRM为例,通过有限元分析仿真,对新型电机结构进行参数化计算,并得到最优结构。在保证平均转矩基本保持不变的情况下,减小了转矩脉动以及径向力。与原始电机相比,转矩脉动系数下降了16.01%,径向力峰值下降了19.96%。因此,证明了该方法对SRM振动抑制有较好的效果,对后续SRM设计及控制具有一定的借鉴意义。     

开关磁阻电机的定子振动模态分析

大的振动和噪声阻碍了开关磁阻电机的推广应用.由于定子的径向振动是开关磁阻电机噪声的主要根源,因此定子振动系统的模态分析是降噪研究的有效手段.该文利用三维有限元法模态分析,通过比较、分析开关磁阻电机定子振动系统的固有频率在不同绕组安装工艺和散热筋结构条件下的变化,得出了加固绕组和采用周向散热筋结构有利于降低开关磁阻电机噪声水平的结论.通过比较一台实验样机的模态分析计算结果和实测结果,证实了模态分析计算的有效性.     

基于物理模型开关磁阻电机定子模态和固有频率的研究

准确计算定子模态和固有频率是降低电机噪声和振动的基础。该文基于开关磁阻电机(SR电机)物理模型，利用3维有限元软件，全面研究了定子模态和固有频率，系统分析了绕组、端盖和安装对定子模态和固有频率的影响。研究表明，对小功率SR电机，2阶模态对噪声和振动的贡献最大。定子绕组对固有频率的影响非常严重，弹性模数远低于实心铜材，绕组不宜采用质量计入磁极或铁心的方式处理。端盖、底脚安装均导致定子固有频率明显升高。最后讨论了2维有限元模型与3维有限元模型计算结果的差异。计算结果与试验结果进行了比较验证。     

开关磁阻电机定子振动的有限元分析

开关磁阻电机(SR电机)定子固有频率的研究对降低电机的噪声和优化控制策略有重要的意义,本文给出了SR电机振动模态分析的数学模型,利用ANSYS有限元软件对不同求解模型进行了详细的计算和分析.结果表明,考虑散热筋、机座和接线盒的三维模型的有限元分析结果与实验测得值有较好的一致性.     

一种新型定子齿极结构的开关磁阻电机电磁分析

给出了一种新型定子齿极结构的开关磁阻电机(SRM)的设计,利用径向力、电磁转矩的解析计算公式,完成了外圆弧形定子磁极结构SRM电磁力特性的计算.计算结果表明,新型结构的定子设计在保证定子极和转子极间切向电磁力基本不变的情况下,大大减小了径向电磁力,这对优化设计SRM结构参数,降低电机运行噪声,延长了电机寿命方面有重大的指导意义.     

Young's modulus for laminated machine structures with particular reference to switched reluctance motor vibrations

The switched reluctance motor (SRM) has a disadvantage of higher acoustic noise, caused by stator vibrations. Techniques for noise reduction require knowledge of the modal frequencies, which depend on mechanical shapes and dimensions as well as material properties, for example, Young's modulus, Poisson's ratio, mass density, etc. It is found that the generally accepted value of Young's modulus is not valid for a machine with laminations and no frame. This paper introduces a simple and nondestructive method for the measurement of Young's modulus; it is then used in a finite-element (FE) program to determine the resonant frequencies of SRM stator vibration. The effects of mass density and Poisson's ratios are also discussed. The FE results are validated by vibration tests, which show good accuracy.     

新型SRM直接转矩控制系统的场路耦合联合仿真

转矩脉动是阻碍开关磁阻电机(SRM)发展的主要因素之一。采取合适的控制策略及结构改进能够抑制转矩脉动,但在研究的过程中通常需要通过仿真的方式进行快速验证。采用Simulink、Maxwell及Simplorer场路耦合多物理域联合仿真的方式,针对新型定转子开槽SRM,建立了直接转矩控制(DTC)系统,模拟分析了其在起动、加减速以及增卸负载等工况下的响应性能,验证了对转矩脉动的抑制效果。对于新型定转子开槽SRM本体建模而言,利用Maxwell建立其有限元模型,可以避免复杂的数学模型推导,且在联合仿真的过程中能够实时反映出电机内部的电磁特性,便于为电机本体结构的改进以及控制策略的优化设计提供重要依据。     

Vector Control Specialized for Switched Reluctance Motor Drives

This paper proposes vector control specialized for a switched reluctance motor (SRM) drive. Because it is a unipolar drive, a sinusoidal current with a dc offset is applied to each circuit instead of the conventional trapezoidal current. The current consists of dc and ac components which can be identified by their generation of a (virtual) rotor flux and rotating stator magnetic field, respectively. Thus, the vector control system can be developed in the same way as conventional ac machines. The proposed technique provides new mathematical models of SRMs on a rotating reference frame and achieves precise and fast torque response and advanced operations such as linear torque‐current control and maximum‐torque‐per‐ampere control. The vector control theory was verified through simulations and experiments.     

一种改进的无轴承开关磁阻电机数学模型

类似于常规开关磁阻电机,无轴承开关磁阻电机的定、转子极宽并非总是相等,通常转子极宽略大于定子极宽,在建立数学模型时应当考虑这一因素.现有的无轴承开关磁阻电机数学模型都存在电机定、转子极宽相等的约束.考虑无轴承开关磁阻电机定、转子极宽可能存在的不相等因素,采用基于直线磁路和变椭圆系数的椭圆形磁路分割法求取气隙磁导,推导出无轴承开关磁阻电机的通用数学模型,使其不仅适用于定、转子极宽相等,而且适用于转子极宽大于定子极宽的情况.以实验室样机为例,将基于所建模型的分析结果与有限元分析结果进行了对比,验证了所建数学模型的正确性,精确度满足工程要求.应用所建立的无轴承开关磁阻电机数学模型,分析了定、转子极宽不等对悬浮力和转矩的显著影响.     

基于DSP的开关磁阻电动机高效调速系统

从能量转换的观点出发,利用模糊神经网络进行开关磁阻电动机(SRM)的非线性建模,得到了SRM开关角度最优控制规律。以TMS320LF2407A数字信号处理器为控制核心,设计开发了具有智能控制方法的高精度SRM系统。试验结果证明,该系统结构简单、可靠,运行效率高,具有很好的静、动态特性。     

6/2结构高速开关磁阻电动机设计研究

开关磁阻电动机（SR电动机）转子上无线圈和永磁体，特别适合高速运行。选择了起动转矩小但适合高速运行的6／2结构SR电动机，利用电磁场仿真软件JMAG对高速SR电动机进行电磁结构设计。通过优化定转子结构，改善了电动机起动特性；搭建了试验平台，给出了电动机初步试验结果。     

土石坝坝基液化土层置换材料关键参数优化

土石坝地震液化可能会引起结构失稳、地基失效等问题,严重威胁工程安全,需要设计采用土层挖除置换的抗液化措施。现有土层置换方案往往根据工程经验进行设计,缺少置换材料的定量化优化分析。本文提出了考虑地震作用下土石坝坝基液化土层的置换材料关键参数优化分析方法,基于实际工程数据,通过数值仿真对土层置换材料进行了优化分析,揭示了置换材料孔隙率、密度、体积模量与剪切模量、黏聚力与内摩擦角四组参数变化对液化的影响规律。结果表明,在土体参数常见取值范围内,孔隙率与密度过小或过大的方案的抗液化效果均较差,模量、内摩擦角较大的方案抗液化效果更好;通过方案比选优化,获得了抗液化效果关键参数的优化数值。随后基于优化参数进行模拟分析,实际工程坝体竖向位移总体得到有效改善,下游坝坡坡率优化率达53.9%,动力计算末液化体积残余值优化率达69.6%。所提出的方法为土石坝置换材料的优化分析提出一种可行手段,对于提高土石坝抗液化性能具有参考意义。