Improved Radial Force Modeling and Rotor Suspension Dynamics Simulation Studies for Double-winding Bearingless Switched Reluctance Motor

The rotor radial force is changed by adjusting the windings current value to control rotor suspension for various kinds of bearingless switched reluctance motor (BSRM). To accomplish the BSRM's suspension control, the radial force analytical model is necessary. Currently the mathematic relationship among radial force, winding currents, and rotor rotation angle has been built for double-winding BSRM, but the rotor eccentricity displacement has not been considered. That is, the existing radial force analytical model only can be used to analyze rotor radial force when rotor shaft is located in the central position. Actually, the rotor radial force is significantly affected by the rotor shaft eccentricity displacement. It is difficult for the bearingless motor to keep the rotor shaft staying in the central position, and the rotor shaft always runs around the central position with an eccentricity displacement. The rotor eccentricity caused by the radial force is considered in the paper to obtain the air-gap permeance and the windings inductances. Furthermore, the radial forces analytical model considering the rotor eccentricity displacement is derived. Finally, the finite-element method (FEM)-based results are applied and the dynamics simulation using the proposed model is accomplished to verify the correctness of the model.     

Torque and suspension force in a bearingless switched reluctance motor

Bearingless switched reluctance motors, which can control rotor radial positions with magnetic force, have been proposed. The bearingless switched reluctance motors are characterized by integration of switched reluctance motors and magnetic bearings. These motors have two kinds of stator windings composed of motor main windings and suspension windings in the same stator in order to produce suspension force that can realize rotor shaft suspension without mechanical contacts or lubrication. For successful stable operation, accurate theoretical formulas of instantaneous torque and suspension force are necessary to a rotational speed controller and a rotor radial position controller. This paper derives the theoretical formulas of the instantaneous torque and the suspension force from an assumption of simple permeance distribution. This derivation process makes an assumption that fringing fluxes are distributed on elliptical lines. It is shown with experimental results that the derived theoretical formulas are very accurate in terms of practical application. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 157(2): 72–82, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20157     

基于有限元法的磁悬浮开关磁阻电机数学模型

当电机高速运行时，为避免机械磨损，采用电磁力进行悬浮支撑，而磁轴承占用轴向空间，限制临界转速。磁悬浮开关磁阻电机利用电机定子与轴承机械结构的相似性，在原有的电机定子绕组上附加一套径向力绕组，通过一定的控制策略，同时实现电机的旋转和悬浮。该文在利用有限元软件Ansoft/ Maxwell 2D分析磁悬浮开关磁阻电机磁场的基础上，结合等效磁回路法并根据虚位移定理，推导出磁悬浮开关磁阻电机在考虑a、b轴方向径向偏移及其耦合时的径向力和转矩的数学模型，并用有限元分析结果验证了该模型的正确性和有效性。     

宽转子无轴承开关磁阻电机的转子极形优化

为了解决宽转子无轴承开关磁阻电机由于开关型供电方式以及双凸极铁心结构在运行过程中容易导致转矩脉动很大的问题,本文对其转子极结构进行改进,提出在转子极两侧开槽的优化设计方案。旨在通过增大开槽处的气隙磁阻,提高用于产生转矩的切向分量的气隙磁密,从而降低转矩脉动。对所开槽进行参数化处理,使用控制变量法分析各开槽参数对转矩性能的影响,以性能指标最优为目标确定开槽参数。利用场路耦合的方法将电机有限元分析模型和直接瞬时转矩控制电路模型结合起来,实现电机系统的动态运行。仿真结果表明转子极开槽后能够有效降低宽转子无轴承开关磁阻电机的转矩脉动,提升平均转矩,并且对径向悬浮力的影响很小。     

无轴承开关磁阻电机磁饱和特性的电磁场分析

阐述了无轴承开关磁阻电机径向悬浮力产生的原理,考虑电机内复杂的磁场饱和情况,定性分析了主、副绕组电流大小对悬浮力的影响.计及磁场饱和,建立了无轴承开关磁阻电机的有限元分析模型,以一台3kW样机为例计算了各种主、副绕组电流组合时的转矩与悬浮力.数值计算结果验证了定性分析所得结果,表明无轴承开关磁阻电机在运行中存在比传统开关磁阻电机更加复杂的磁饱和现象,磁饱和使得电机悬浮力与绕组电流关系严重非线性,而且悬浮力大小并非总是随绕组电流的增加而增加,存在随电流增加悬浮力减小的情况,这必然给稳定悬浮控制带来困难.     

无轴承开关磁阻电机实验平台的设计与实现

将无轴承技术应用于开关磁阻电机中可充分发挥该电机的高速适应性,并拓宽其在微型和大功率领域中的应用。该文在已有数学模型基础上,针对其电磁转矩和悬浮力的控制特点,设计了以DSP-LF2407A为控制核心的数模混合控制实验平台。实验平台包括无轴承开关磁阻电机本体、DSP数字控制器、电流滞环控制器、PID调节单元、3套功率逆变器、传感器和相关辅助电路,并对其工作原理进行了分析。在此基础上设计了控制系统的软件,并给出了主要子程序的流程图。通过对整个实验平台硬软件的联合调试,实现了无轴承开关磁阻电机的稳定悬浮。     

基于三相半桥功率变换器的无轴承开关磁阻电机绕组结构分析

无轴承开关磁阻电机兼有开关磁阻电机和磁轴承的优点。功率变换器是无轴承开关磁阻电机的重要组成部分,其控制绕组电流,对电机旋转和悬浮性能有重要影响。悬浮绕组功率变换器采用三相半桥结构时,由于负载的不对称,存在中点电压漂移问题。该文简要介绍了电机悬浮原理和数学模型,将功率变换器和电机作为一个整体,分析了中点电压漂移的原因及绕组配置对中点电压的影响。给出了5种绕组结构形式下,各相悬浮力之和及其对中点电压的影响。通过合理配置绕组结构,使电机在恒定径向负载的情况下,中点电压波动大为减小。给出了4种优化的无轴承开关磁阻电机绕组结构。实验结果证明了理论分析的正确性。     

单绕组无轴承永磁薄片电机的原理和实现

研究了一种单绕组无轴承永磁薄片电机的工作原理和结构设计。摒弃了传统无轴承电机的双绕组结构,采用一套绕组实现电机转子悬浮和旋转。推导了单绕组无轴承永磁薄片电机径向悬浮力的数学模型,给出相应的控制策略和功率系统设计方案。制作了实验样机,并做了空载和负载实验。实验样机调试结果表明,单绕组无轴承永磁薄片电机成功实现了包括径向、轴向和扭转等方向的5自由度全悬浮。     

Improved analysis of a bearingless switched reluctance motor

Bearingless switched reluctance motors, which can control rotor radial positions with magnetic force, have been proposed. Bearingless switched reluctance motors have combined characteristics of switched reluctance motors and magnetic bearings. Production of radial force for rotor shaft magnetic suspension is explained with differential stator windings. Mathematical relations between motor currents and radial force are derived by considering cross coupling and fringing fluxes. Theoretical relationships are verified with experimental results at partial overlap positions     

Analysis and characteristics of a permanent magnet-type bearingless motor

Super-high-speed and high-power electric machines are required for turbomolecular pumps and spindle drives. High rotational speed and high-power drives can be achieved with bearingless motors. In this paper, a bearingless motor with principles of permanent magnet-type synchronous motors is proposed. High-power factor and high efficiency can be expected in permanent magnet-type bearingless motors. The proposed bearingless motor is a 4-pole permanent magnet synchronous motor, in which additional 2-pole windings are wound together with 4-pole motor windings in stator slots. With currents of 2-pole windings, radial magnetic forces are produced to support a rotor shaft. Principles of radial force production of surface-mounted permanent magnet bearingless motors are analyzed mathematically. The relationships between radial forces and the permanent magnet thickness were derived. From these relationships, the optimal permanent magnet thickness to produce radial forces efficiently is found. A test machine was built to confirm the relationships of radial forces, currents and voltages.     

无轴承开关磁阻电机转子质量偏心补偿控制

由于机械不平衡原因,无轴承开关磁阻电机存在转子质量偏心的问题,这会导致额外的不平衡径向磁拉力,从而使电机的悬浮精度变差,这也是限制电机高速时转速进一步提升的重要因素。分析转子质量偏心对电机悬浮性能的影响,介绍悬浮转子振动控制原理,设计基于最小均方（least—mean—square,LMS）算法的白适应凹陷滤波器,将其加入到无轴承开关磁阻电机（bearinglessswitchedreluctancemotor,BSRIV1）系统中,利用Matlab／Simulink对该振动控制方法进行仿真研究,最后在一台实验样机上进行实验验证。结果表明,基于LMS算法的白适应凹陷滤波器能够在不同的电机转速条件下有效补偿转子的同频振动位移,抑制转子偏心振动,提高转子悬浮精度。     

无轴承永磁同步电机有限元分析

无轴承永磁电机径向悬浮力与电机绕组结构、永磁体厚度及悬浮力绕组中电流等存在着复杂关系，研究这些关系对电机优化设计具有重要参考价值。该文在介绍了无轴承永磁同步电机径向悬浮力产生原理基础上，推导了径向悬浮力数学模型。用有限元分析和计算方法，讨论了无轴承永磁同步电机在定子绕组相应等效电流作用下，改变径向悬浮力绕组中的电流，电机气隙磁路分布状况；在电机气隙不变，改变永磁体厚度，计算和分析了径向悬浮力与永磁体厚度之间的关系；在电机转矩绕组极对数pM=2不变的情况下，对径向悬浮力绕组采用一对极pB=1和三对极pB=2方式绕制，计算和比较产生的径向悬浮力和麦克斯韦力大小。对pM=2，pB=3的实验样机，在静态悬浮状态下，测试了径向悬浮力和径向悬浮力绕组电流之间的关系，实验结论验证了ANSYS软件计算结果的正确性。     

新型无轴承开关磁阻电机双相导通数学模型

针对传统无轴承开关磁阻电机数学模型单相电流导通模式的局限性,提出了一种适用于单、双相导通的无轴承开关磁阻电机数学模型.在建立两相电流导通的等效磁路模型基础上,确定电感矩阵,推导出两相电流导通的径向悬浮力和电磁转矩的表达式.基于该数学模型的双相电流导通模式极大程度地拓宽了无轴承开关磁阻电机的工作区域,增加了其承受径向负载的能力.利用磁场分析法验证了该数学模型的正确性和优良的工作特性.     

基于神经网络逆系统的磁悬浮开关磁阻电动机的解耦控制

磁悬浮开关磁阻电动机作为一个多变量、非线性和强耦合的系统,其控制系统的设计非常复杂.对于磁悬浮开关磁阻电动机来说,得到径向力和平均转矩的先验知识是实现电机闭环控制的基本条件.基于基本电磁场理论,论文给出磁悬浮开关磁阻电动机的径向力模型,对该模型进行可逆性分析,证明该系统可逆,应用神经网络逆系统方法实现径向力的动态解耦,以便达到高性能的控制目的,仿真结果验证了方法的可行性.     

基于麦克斯韦应力法的双绕组无轴承开关磁阻电机新型数学模型

现有的双绕组无轴承开关磁阻电机麦克斯韦应力法数学模型忽略了相互垂直方向上径向悬浮力的耦合,但当转子偏离定转子齿极中心对齐位置较大时存在较强的耦合,故现有模型难以满足高精确度稳定悬浮控制要求。选择一种计及相互垂直方向悬浮力耦合的新积分路径,建立了基于麦克斯韦应力法的双绕组无轴承开关磁阻电机新型数学模型,同时为计及电机磁路的饱和特性,采用最小二乘法对铁心材料的非线性磁化曲线进行拟合,求解考虑磁饱和的各气隙磁密。通过与有限元仿真结果对比,验证了所建模型不仅揭示了相互垂直方向上径向悬浮力的耦合关系,考虑了磁饱和特性,且具有精确度良好、计算量小等优点,为实现高精度稳定悬浮控制奠定了基础。     

无轴承永磁同步电机控制系统设计与仿真

无轴承永磁同步电机是自身具有磁悬浮轴承功能的新型特种电机，是一个复杂的强耦合的非线性系统，建立无轴承永磁同步电机径向悬浮力和电机数学模型，是设计无轴承永磁同步电机控制系统的前提，实现其径向悬浮力和电磁转矩之间的解耦控制是电机稳定运行的基本条件。该文在介绍无轴承永磁同步电机径向悬浮力产生原理的基础上，推导了径向悬浮力和电机数学模型，采用基于转子磁场定向控制策略设计了无轴承永磁同步电机矢量控制系统，利用Matlab的Simulink工具箱构建了矢量控制系统，对无轴承永磁同步电机的转速、转矩及转子起浮性能进行了仿真。仿真结果表明控制系统不仅可以实现转子稳定悬浮，而且电机具有良好的动态性能。     

双定子磁悬浮开关磁阻电机直接转矩与直接悬浮力控制

研究一种双定子磁悬浮开关磁阻电机。该电机采用内-外双定子结构,内定子和外定子上分别设置悬浮力绕组和转矩绕组。在结合拓扑结构说明其运行原理的基础上,针对该电机同时存在转矩脉动和悬浮力脉动过大的问题,提出了直接转矩(DT)与直接悬浮力控制(DSFC)策略。比较了传统方波控制策略与所提控制策略下系统的转矩脉动、悬浮力脉动以及转子径向位移波动。仿真结果表明:DT/DSFC不仅能提高系统动态响应速度,而且有效抑制了转矩和悬浮力脉动,削弱了转子径向抖振,验证了所提控制策略的有效性与优越性。     

基于等效磁网络法的混合励磁双定子磁悬浮开关磁阻电机建模研究

提出了一种混合励磁双定子磁悬浮开关磁阻电机(BSRM)的等效磁网络模型,此模型可以分析电机悬浮和转矩绕组的磁链、电感及悬浮力和转矩等静态特性。等效磁网络法(EMN)不仅能保证一定的精度,而且比有限元法(FEM)节省时间。基于一种24/16/8极混合励磁双定子BSRM建立EMN模型,推算出电机定转子齿部、轭部以及气隙磁导的计算公式。建立矩阵方程,求解出各部分的磁通密度,进而求出悬浮和转矩绕组的磁链、电感以及悬浮力和转矩特性,和FEM求解的结果进行对比。可以发现EMN模型求解出的电磁特性和FEM分析的结果吻合效果很好,进一步证明了所建模型的有效性。     

两种不同转子结构的无轴承同步磁阻电动机悬浮特性分析

提出一种新型的轴向叠片各向异性转子无轴承同步磁阻电动机,并将该电机与传统凸极转子无轴承同步磁阻电动机进行了悬浮特性对比分析.分别详细论述空载和负载条件下两种转子结构电机的悬浮运行原理,给出了样机设计参数,并对上述两种无轴承同步磁阻电动机的悬浮力进行有限元计算与分析,证实轴向叠片各向异性转子无轴承同步磁阻电动机能更加有效...     

Magnetic suspension force in an induction bearingless motor with a squirrel cage rotor

Theoretical equations of magnetic force in an induction bearingless motor have been reported. In the bearing‐less motor, both 4‐pole and 2‐pole windings are stored in stator slots for torque and suspension force generation. In the analysis, squirrel cage rotor currents are considered. These currents are induced by both torque and suspension winding currents. Inductance matrix is represented by four sets of three‐phase windings, thus a 12×12 matrix is constructed. A simplification and reasonable assumptions are introduced to obtain understandable expressions for suspension force and torque representation. The rotor flux linkages in an induction bearingless motor are derived, and a simulation model of suspension force is then constructed. It is shown that the response and the phase of suspension force are delayed in the case of cage rotors. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(3): 77–87, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20340