Calculation and analysis of unbalanced magnetic pulls of different stator winding setups in static eccentric induction motor

In large-scale electric machines, unbalanced magnetic pull （UMP） caused by eccentricity usually results in stator-rotor rub, so it is necessary to investigate the amplitude and the influencing factors. This paper takes the squirrel-cage induction motor as an example. A magnetic loop model of an induction motor is established by an analytical method. The impact of stator winding setup （parallel branch and pole pairs） on each magnetomotive force （MMF） and unbalanced magnetic pull is analyzed. Using the finite element simulation method, the spatial and time distribution of flux density of the rotor outer circle under static eccentricity is obtained, and the unbalanced magnetic pull calculation caused by static eccentricity is completed. The conclusion of the influence of stator winding on the size of unbalanced magnetic pull provides reliable gist for motor noise and vibration analysis, and especially provides an important reference for large induction motor design.

A Novel Part-Winding Starting Method for 4-Pole Squirrel Cage Induction Motor

the paper has been removed due to the authors' personal reason.

Harmonics in the Squirrel Cage Induction Motor,Analytic Calculation Part Ⅱ:Synchronous Parasitic Torques,Radial Magnetic Forces

The magnetic field generated in the air gap of the cage asynchronous machine and the harmonics of the magnetomotive forces creating that magnetic field,as well as the synchronous parasitic torques,radial magnetic forces have been discussed in great detail in the literature,but always separately,for a long time.However,systematization of the phenomenon still awaits.Therefore,it is worth summarizing the completeness of the phenomena in a single study–with a new approach at the same time-in order to reveal the relationships between them.The role of rotor slot number is emphasized much more than before.New formulas derived for both synchronous torques and radial magnetic forces are used for further investigation.It will be shown that both phenomena in subject must be treated together.Formulas will be provided to take into account attenuation.Design guide will be provided to avoid dangerous rotor slot numbers.It will be shown that the generation of synchronous torques and radial magnetic forces do not depend–in this new approach-on the slot combination,but on the rotor slot number itself.

Harmonics in the Squirrel Cage Induction Motor Analytic Calculation-Part Ⅰ: Differential Leakage, Attenuation, Asynchronous Parasitic Torques

The magnetic field generated in the air gap of the cage asynchronous machine and the harmonics of the magnetomotive forces creating that magnetic field, as well as the related differential leakage, attenuation, asynchronous parasitic torques have been discussed in great detail in the literature, but always separately, for a long time. However, systematization of the phenomenon still awaits. Therefore, it is worth summarizing the completeness of the phenomena in a single study – with a new approach at the same time-in order to reveal the relationships between them. The role of rotor slot number is emphasized much more than before. An existing, commonly used, but still impractical basic figure has been modified to more clearly demonstrate the response of the rotor for the harmonics of the stator. The need to treat differential leakage, asynchronous parasitic torques and attenuation together will be demonstrated: new formula for asynchronous parasitic torque is derived;the long-used characteristic curves for differential leakage and attenuation used separately so far was merged into one, correct curve in order to provide a correct design guide for the engineers.

The time and space characteristics of magnetomotive force in the cascaded linear induction motor

To choose a reasonable mode of three-phase winding for the improvement of the operating efficiency of cascaded linear induction motor, the time and space characteristics of magnetomotive force were investigated. The ideal model of the cascaded linear induction motor was built, in which the B and C-phase windings are respectively separated from the A-phase winding by a distance of d and e slots pitch and not overlapped. By changing the values of d and e from 1 to 5, we can obtain 20 different modes of three-phase winding with the different combinations of d and e. Then, the air-gap magnetomotive forces of A-, B-, and C-phase windings were calculated by the magnetomotive force theory. According to the transient superposition of magnetomotive forces of A-, B-, and C-phase windings, the theoretical and simulated synthetic fundamental magnetomotive forces under 20 different arrangement modes were obtained. The results show that the synthetic magnetomotive force with d = 2 and e = 4 is close to forward sinusoidal traveling wave and the synthetic magnetomotive force with d = 4 and e = 2 is close to backward sinusoidal traveling wave, and their amplitudes and wave velocities are approximately constant and equal. In both cases, the motor could work normally with ahigh efficiency, but under other 18 arrangement modes （d= 1, e=2; d= 1, e=3; d= 1, e=4;...）, the synthetic magnetomotive force presents obvious pulse vibration and moves with variable velocity, which means that the motor did not work normally and had high energy loss.

Sensorless Vector Control of Induction Generators for Variable-Speed Wind Turbines Using Micro-2407

A sensorless vector-control strategy for an induction generator in a grid-connected wind energy conversion system is presented. The sensorless control system is based on a model reference adaptive system (MRAS) to estimate the rotational speed. In order to tune the MRAS observer and compensate for the parameter variation and uncertainties, a separate estimation of the speed is obtained from the rotor slot harmonics using an algorithm for spectral analysis. This algorithm can track fast dynamic changes in the rotational speed, with high accuracy. Two back to back pulse width modulated (PWM) inverters are used to interface the induction generator with the grid. The front-end converter is also vector controlled. The dc link voltage is regulated using a PI fuzzy controller. The proposed sensorless control strategy has been experimentally verified on a 2.5-kW experimentally set up with an induction generator driven by a wind turbine emulator. The emulation of the wind turbine is performed using a novel strategy that allows the emulation of high-order wind turbine models, preserving all of the dynamic characteristics. The experimental results show the high level of performance obtained with the proposed sensorless vector-control method.

Research on dual-stator winding multi-phase high-speed induction generator with rectifier load

Based on analysis and calculation of the relation between current harmonics and MMF harmonics in the dual-stator winding multi-phase high-speed induction gen-erator with a rectifier load, a new idea, which divides the generator system into two sub-systems to be analyzed individually, is presented. For the sub-system of the 12-phase power winding with a rectifier load, the loop current method is used to establish network equation set in terms of the network graph theory. The numerical stability problem is solved by alternating use of fixed time-step and varied time-step, and the voltage and current with their fundamental components of the power winding are obtained. For the other sub-system of the induction generator with dual-stator winding and solid cage rotor, the electromagnetic field analysis method and the multi-variable optimization approach are combined to get the con-trol winding current and stator frequency. Calculated results well match experiment results, indicating that the new proposed method is of effectiveness and high ac-curacy.

CALCULATION OF THE HARMONIC LEAKAGEOF IRREGULAR WINDINGS

This paper, based on the harmonic analysis and the harmonic e-quivalent circuit of the induction motor, clearly discusses the damping effectof harmonic current in the rotor and incorporates the slot-mouth factor to thewinding factor. The practical computi

感应电动机中三相不对称绕组

对具有三相不对称交流绕组的感应电动机进行研究,对已有的研究成果进行分析与对比。在对称分量变换下建立了采用序阻抗表达的对称绕组相电压方程,得到了相绕组的自漏阻抗和互漏阻抗与等效阻抗和零序阻抗之间的关系。根据不对称绕组的实际情况,将等效阻抗和零序阻抗分别乘上不同的系数,建立了新的电压方程。采用磁动势分量进行了坐标变换,实现了电压方程的解耦,使计算得到简化。最后,通过实验对计算数据进行了验证。

Analysis of Vibration and Noise of Induction Motor Equipped with Concentric Single-Double-Layer Star-Delta Winding

Compared with changing the structure of a motor that has been manufactured,changing the type of stator winding is an economical and time-saving method to reduce the vibration and noise.Thus,a concentric single-double-layer star-delta(CSDLSD)winding for an induction motor is described in this paper with the aim of reducing the noise of the motor.By planning the turns relationship between the two parts of the winding,the harmonic component of the air-gap magnetic field can be decreased.Besides this,through adjusting the turns ratio in each slot of concentric winding per phase respectively,the waveform of the air-gap magnetic field becomes closer to a sinusoidal type.Three motors equipped with the CSDLSD winding and another two types of stator winding were analyzed.The theoretical analysis and the two-dimensional finite element method(2D-FEM)were combined to study the relationship between the harmonics of the air-gap magnetic field and the stator winding.Finally,a 2D fast Fourier transformation(2D-FFT)method was used to obtain the time-frequency spectrum of the air-gap flux density and electromagnetic excitation force,and compared with a natural vibration wave.The noise distribution was obtained using the harmonic response.The results of the theoretical analysis,2D-FEM,2D-FFT,and harmonic response corroborate each other such that the motor applying CSDLSD winding could reduce both the vibration and noise.

异步电机综合故障实验教学平台设计与开发

由于异步电机实验教学平台多是针对正常工况设计开发的,缺乏对故障状态的模拟和分析,因此造成了教学和实际需求的脱节。该文设计开发的异步电机综合故障实验教学平台可以开展定子绕组匝间故障、转子断条故障、轴承故障实验和在线诊断,该平台综合了异步电机拆解与组装、故障特征分析以及数字信号处理技术的实际应用,有助于学生深入理解相关知识,提升实际动手能力。

高速轴向磁通永磁电机环形绕组电感计算

高速轴向磁通永磁电机在小功率发电机组上有潜在应用前景。为消除齿谐波,高速轴向磁通电机一般采用无槽铁心和环形绕组结构。为了研究该绕组的电感,采用磁势法和绕组函数法给出了该绕组的电感解析表达式,能计入绕组基波和谐波对电感的影响。采用有限元方法验证了电感解析解的正确性。给出的结论对高速轴向磁通电机的后续稳态、瞬态分析提供了理论参考。

双馈感应电机无速度传感器直接转矩控制方法

风电机组双馈感应发电机运行中,由于参数变化的不确定性导致其无速度传感器直接转矩控制输出值出现异常波动,为保证双馈感应电机的频率稳定性,提出一种双馈感应电机无速度传感器直接转矩控制方法。计算转子磁链同步转速和转差速度,得到发电机的转速观测值;分析转子绕组电压空间矢量,建立磁链模型并构建电磁矩阵,在矩阵中计算定子绕组和转子绕组的磁势矢量,通过二者的矢量积得到电机的电磁转矩;转速和转矩共同组成直接转矩控制系统,实现对电机的速度调节和控制。仿真分析结果表明:采用所提方法时,在双馈感应电机启动后转速迅速增加,且在1.2 s后转速始终保持为1400 r/min,可保证转子磁链的运行轨迹接近于圆形,直接转矩控制效果平稳。

轴承故障工况下无刷直流电机的电感参数计算

航空航天领域的电机发生轴承故障时无法立即停机检修,需要短时间内容错运行,为了解决运行中轴承故障量化问题,通过绕组电感变化表达轴承故障程度。文章分析了滚动轴承故障机理,根据滚动轴承不同部件故障的特点,建立了基于绕组函数法的解析模型计算轴承外圈、内圈、滚动体故障时的绕组电感,建立了有限元模型计算轴承保持架故障时的绕组电感。结果表明:无刷直流电机轴承故障后的电感会高于正常值,出现波动,其幅值与频率取决于轴承故障程度。

电源含低次谐波时感应电机振动特性及降振措施研究

感应电机因其可靠性高、易维护的优点成为工业领域风机、压缩机及泵类负荷的主要驱动设备,随着变频器与非线性负载的大量应用,导致供电电源包含明显低次谐波进而显著影响电机低频段振动特性。受设备安装空间与滤波成本的限制,增设滤波装置消除电源侧低次谐波的难度颇大。为了削弱上述不利影响,从理论角度分析了电源含低次谐波对径向电磁力的影响,并以一台32 kW感应电机为例,设计了一种低谐波绕组方案用于削弱低次谐波对电机低频段振动的影响,进一步利用时步有限元法对比分析了采用普通绕组与低谐波绕组方案时电机的径向磁密和径向电磁力特点,结果表明文中低谐波绕组方案能够有效降低气隙磁密低次谐波分量及低阶次径向电磁力幅值。通过现场实验验证了低谐波绕组方案能够有效抑制低频段振动。

开绕组异步电机零序电流控制策略

零序电流抑制是共母线和共中线开绕组拓扑应用所必须解决的技术问题,为了探讨虚拟信号重构思想在零序电流控制上的应用,并对比各种虚拟信号重构控制方案间的差异。通过对虚拟三相电流和虚拟两相电流方案进行数学分析,建立了虚拟电流方案的统一数学模型,并依据控制系统频域分析方法,从理论上揭示了各方案间的性能异同。基于三相时延、正交时延、一阶全通滤波器、二阶低通滤波器、二阶全通滤波器以及巴特沃斯滤波器搭配微分的虚拟信号重构方案间具有类似的控制性能,在应用中可以互相替换;而基于二阶广义积分器的方案相较于上述各方案具有更突出的动态响应性能,但会在控制带宽过大时失去稳定。最后,通过共中线开绕组异步电机零序电流的控制对理论分析的正确性进行了验证。

电动汽车用绕组切换型永磁同步磁阻电机设计与分析

永磁同步磁阻电机结合了永磁同步电机和同步磁阻电机的优点,广泛应用于电动汽车,是电机领域的一大研究热点。分别采用辐式磁极和V形磁极设计了两台永磁同步磁阻电机,每台电机都设计了可串、并联切换的电机绕组,以进一步拓宽电机的调速范围。为减小转矩脉动,电机采用不均匀气隙。分析了两种转子电机在定子绕组串、并联模式下的交、直轴电感的特点,以及不均匀气隙对电机性能的影响。研究表明V形磁极电机较辐式磁极电机具有更大凸极率,在电机串联运行时可以获得更大的磁阻转矩,合理的不均匀气隙可以改善电机的性能。样机测试结果验证了上述分析的正确性。

基于Lyapunov理论的异步电机定子绕组匝间短路故障检测系统设计

为实现对定子绕组匝间短路故障行为的精准识别,确保异步电机的稳定运行状态,设计了基于Lyapunov理论的异步电机定子绕组匝间短路故障检测系统;在DSP外围电量回路中,设置ARM处理器与步进电机驱动模块,采用模数转换单元结构,调节电量互感装置的实时运行状态,实现对异步电机定子绕组匝间短路故障检测系统硬件设计;根据Lyapunov函数定义条件,确定Nussbaum增益参数取值范围,在此基础上,定义Lyapunov算法模型,再通过计算故障预测特征的方法,求解定子绕组的短路故障电压方程与匝间电感参数,对定子绕组匝间短路故障特征进行分析,实现异步电机定子绕组匝间短路故障检测;实验结果表明,所设计系统可以有效控制定子绕组匝间短路故障电流和电压检测结果与非干扰条件下检测结果之间的差值水平,能够精准识别定子绕组匝间短路故障行为,保障异步电机的稳定运行状态。

基于定转子分数槽集中绕组的感应电机起动转矩特性分析

为对双馈风力发电机的启动转矩分析提供支持,针对双馈感应电机极对数多、功率因数低、很难实现大转矩的问题,采用分数槽集中绕组结构对双馈感应电机的绕组进行了优化。通过对比有限元仿真和实验数据,分析得出外电路激励下电机启动转矩随转子初始位置参变量而变化,寻找到最大转矩下的定转子轴线夹角,并利用公式推导证明了这一结论。