Radial force and torque of a bearingless switched reluctance motor operating in a region of magnetic saturation

Bearingless switched reluctance motors, which can control rotor radial positions with magnetic force, have been proposed. These motors are characterized by integration of switched reluctance motors and magnetic bearings. It is essential for a control system to consider magnetic saturation in real time in order to realize stable operation at a full torque load. Thus, this paper proposes a method for fast calculation of radial force and torque of a bearingless switched reluctance motor operating in a region of magnetic saturation. It is shown experimentally that the proposed method is effective in calculating the radial force and the torque under conditions of magnetic saturation.     

A method of determining the advanced angle of square-wave currentsin a bearingless switched reluctance motor

Bearingless switched reluctance motors, which can control rotor radial positions with magnetic force, have been proposed. These motors have combined the characteristics of switched reluctance motors and magnetic bearings. This paper proposes a method of determining the advanced angle of square-wave currents in a bearingless switched reluctance motor. Under any torque condition, from no load to full load, stable operation is realized by controlling the advanced angle of square-wave currents with the proposed method. It is shown experimentally that the proposed method is effective in realizing stable operation     

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     

磁悬浮开关磁阻电动机转子径向偏心时的仿真

磁悬浮开关磁阻电动机结合了开关磁阻电动机和磁轴承的特点,通过电磁力控制转子径向位置。分析了磁悬浮开关磁阻电动机悬浮力和旋转力的产生原理。基于开关磁阻电动机转子的四个特殊位置,利用二维有限元方法分析了转子位于中心位置与有径向偏心时的电机内部磁场,给出了磁场分布图、径向悬浮力与径向偏心矩的关系曲线、旋转力与径向偏心矩的关系曲线,为进一步描述磁悬浮开关磁阻电动机悬浮力与旋转力的模型提供了依据。     

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。     

Inherently decoupled magnetic suspension in homopolar-typebearingless motors

The authors have proposed bearingless motors, that is, magnetic bearings combined with motors in the same stator. It is possible to reduce their shaft length compared with a conventional motor with magnetic bearings, and to achieve higher rotational speed. Bearingless motors generate radial force by adding n ± 2-pole flux on n-pole motor flux to make the flux distribution unbalanced. Several types of bearingless motors have already been proposed, and most of them require variations of motor flux to be taken into account to maintain stable radial position control. In this paper, homopolar-type bearingless motors are proposed and their radial force is analyzed. The rotor of a homopolar motor has two cores with salient poles, and each core is magnetized in a single pole. The important characteristics that the radial force does not vary in accordance with the rotor angle or the motor torque current are derived from analysis. It is confirmed by experiments that the radial position can be controlled nearly independently from the rotational angle and torque     

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。     

基于定转子开窗的混合励磁双定子BSRM振动抑制

无轴承开关磁阻电机(BSRM)由于容错性高、损耗小、效率高等优点在工业领域已得到广泛应用,但电机运行时振动会限制其在某些领域的应用。以混合励磁双定子BSRM为研究对象引入一种在定转子齿部开窗的方法,通过改变外定子或转子铁心磁阻大小,可以减小气隙中的磁密大小,达到减小电磁振动的目的。采用电磁有限元法与正交试验法优化窗口的位置和尺寸,验证转子开窗对外定子径向力和转矩的影响,最后通过模态叠加法验证转子开窗对振动响应的影响。结果表明,该方法对混合励磁双定子BSRM电磁振动有较好的抑制效果但对电机转矩有一定影响。     

Radial Force Analytic Modeling for a Novel Bearingless Switched Reluctance Motor When Considering Rotor Eccentricity

Abstract—Analytic modeling of radial forces is proposed for the novel bearingless switched reluctance motor, where the rotor eccentricity is taken into account. The novel bearingless switched reluctance motor's model is never disclosed, even though there are many advantages, such as fewer suspension windings and simpler control circuit and algorithm, when compared to the conventional bearingless switched reluctance motor. The analytic model of radial forces is very important to achieve this new bearingless switched reluctance motor's suspension control. The rotor eccentricity is a key cause to affect the radial forces. This article calculates the air-gap permeances through considering rotor eccentricity. The self-inductance and mutual-inductance expressions of the motor torque windings and the suspension windings are derived by using the magnetic equivalent circuit method. The derived radial force model discloses the effects of winding currents, rotor position angle, and rotor eccentricity displacement. The finite-element analysis based results verify the built model.     

无轴承异步电机的最大径向力有限元分析

无轴承电机是集成了径向磁轴承功能的高速电机 ,由于功率密度大、结构紧凑 ,它是大功率高速电机的发展趋势。本文利用有限元方法 (FEM)分析了无轴承异步电机的磁场 ,给出了磁场分布图 ,利用气隙磁密的分布计算了作用于转子的径向力。研究表明 ,径向力绕组电流和径向力大小之间的关系受电机磁饱和的影响 ,可计算出最大径向力。本文形象地揭示了无轴承异步电机的径向力产生机理 ,为准确描述径向力的数学模型奠定了基础     

无轴承永磁薄片电机径向悬浮力精确数学建模

无轴承永磁薄片电机具有薄片转子的特殊结构,为了采取有效方法控制转子偏心位移、使转子稳定悬浮,研究的关键在于获得无轴承永磁薄片电机精确的径向悬浮力数学模型。在介绍无轴承永磁薄片电机的结构和工作原理基础上,对无轴承永磁薄片电机气隙磁场进行了详细分析,基于麦克斯韦应力张量法推导了其径向悬浮力数学模型,最后对比验证了利用有限元方法的计算结果和样机实验对数学模型的理论计算结果。验证结果表明,该方法建立的径向悬浮力数学模型误差小、精确度髙。     

磁悬浮开关磁阻电动机研究

磁悬浮开关磁阻电机是高速电机领域的一个研究热点。分析了磁悬浮开关磁阻电机的基本原理，对电机数学模型的发展进行了详细的论述，在考虑和不考虑转子偏心的情况下对磁悬浮开关磁阻电机的磁场作了有限元分析和计算。有限元分析结果验证了电机数学模型的有效性。还介绍了磁悬浮开关磁阻电机空载和负载的实验情况，针对磁悬浮电机的非线性、多变量、强耦合的特点引进了一些先进的解耦控制算法。仿真结果验证了各控制算法的可行性。     

双凸极电机电磁力的有限元分析

双凸极电机的径向磁吸力是电机产生振动与噪声的主要来源。该文运用有限元方法,对1台双凸极结构的开关磁阻电机进行了径向磁吸力的计算,得到了径向磁吸力与转子位置角及相电流的关系。其结论为描述双凸极电机径向磁吸力的非线性模型奠定了基础,同时对于设计优化电机结构以减小振动与噪声有较好的指导意义。     

开关磁阻轮毂电机非线性建模及驱动控制仿真

针对开关磁阻轮毂电机气隙偏心产生的不平衡径向力对车辆平顺性造成的不利影响,提出一种基于电流斩波的脉冲调制控制（PWM）的方法抑制开关磁阻轮毂电机不平衡径向力,从根本上改善车辆平顺性。首先通过Ansoft Maxwell 对一台8/6极四相开关磁阻电机进行有限元分析,在获取电机特殊位置电感数据的基础上,采用傅里叶级数拟合的方法建立开关磁阻电机非线性模型,并与有限元分析结果做对比验证了该模型的准确性。在此基础上建立开关磁阻轮毂电机驱动模型和轮毂电机驱动电动汽车机电耦合一体化模型,将所提出基于电流斩波的PWM控制方法与传统电流斩波控制方法对车辆平顺性影响做对比,仿真结果显示基于电流斩波的PWM控制方法能有效降低开关磁阻轮毂电机不平衡径向力的大小,在提高电机输出转矩的同时改善轮毂电机驱动电动汽车平顺性。     

基于高频脉冲注入的无轴承开关磁阻电机转子位置与径向位移检测方法

为提高无轴承开关磁阻电机(BSRM)的集成度和运行可靠性,探索无轴承电机的转子转角和径向位移的自检测方法,通过在BSRM非导通相的主绕组中注入高频脉冲信号,实现了同时检测转子的转角位置和径向位移的目的。一方面,利用绕组电流的斜率差值与绕组电感的关系,得到BSRM电感的实时分布信息,从而解算得到转子的实时转角位置。另一方面,通过检测悬浮绕组的感应电动势来获取主、悬浮绕组间的互感信息,利用互感与转子径向位置的关系,解算得到转子的实时径向位移。从而最终仅通过对主绕组注入一组高频脉冲来同时估测BSRM的转子转角和径向位移。实验结果证实了所提方法的有效性。     

径向力激发噪声最小的开关磁阻电动机开关角优化

开关磁阻电机噪声主要是其径向力波使二阶振型模态产生偏移引发的.针对开关角是开关磁阻电机中两个最为重要的控制参数的特点,提出了开关磁阻电机电压PWM控制方式下开关角的两次在线寻优方法.寻优原理以径向力激发的二阶振型模态最高噪声声级最小为目标,并依据寻优步长不同实行两次优化搜索.仿真结果表明,两次在线寻优的开关角能使开关磁阻电机运行时激发的二阶振型模态最高噪声声级显著降低,从而使得整体噪声减小.     

无轴承开关磁阻电机的功率变换器研究

无轴承开关磁阻电机结构简单、运行效率高、容错能力强,具有良好的高温和高速适应性。介绍了无轴承开关磁阻电机的悬浮原理和系统构成,简要分析了其控制策略。根据其控制特点,设计了主绕组和悬浮绕组功率电路拓扑结构,通过实验样机验证了功率电路的可靠性。     

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。     

无轴承开关磁阻电机径向电磁力模型

针对现有无轴承开关磁阻电机数学模型忽略磁饱和或对磁饱和考虑不充分的不足,将麦克斯韦张量法和磁路分析法结合起来,提出了一种计算无轴承开关磁阻电机径向电磁力的方法.该方法考虑了电机运行过程中磁饱和以及转子的偏心位移,能够准确的描述电机径向电磁力的特性,为电机运行状态的离线分析和电机的设计提供了更为可靠的理论依据;该模型同时为无轴承开关磁阻电机电磁振动和噪声的预测与控制提供了理论依据.以一台实验样机为例,建立了考虑磁饱和的无轴承开关磁电机有限元分析模型.仿真结果证明了该解析模型的有效性.