基于有限元法的开关磁阻电机磁场特性分析

为了准确掌握开关磁阻电机的磁场特性,建立了其磁场二维模型,采用电磁场有限元方法对开关磁阻电机的磁场分布特性和参数进行分析计算。结果表明：在定子齿极与转子齿极完全不重合时,有限元分析因端部磁场的作用产生较大的误差,相对误差约为40%;随着定子齿极与转子齿极重合量的增加,有限元的计算误差逐步减小,到对齐位置时,漏磁很小,自感漏磁几乎为零。研究结果为电机结构的优化设计提供了理论依据。     

圆筒型双Ω定子横向磁通永磁电机建模分析

双Ω型定子横向磁通永磁直线电机在同一个电枢上通过整合两组定子铁心的方式使得其结构更加紧凑,其空间利用率高、效率高、功率密度大。在分析新型双Ω定子横向磁通永磁直线电机的基础上设计了两类圆筒型的双Ω定子横向磁通永磁电机,采用有限元分析方法(FEA)分别对两类电机的气隙磁密波形、反电势、磁链及电磁转矩参数进行比较分析。结果表明:三相结构更加紧凑,适用于对电机体积限制严格、转矩高的场合;单相结构的磁通密度分布、反电势、磁链参数波形更为理想,在电机精度要求较高的场合可选择该结构。     

无转速传感器抽油电机扭矩在线监测系统研究

介绍了一种无转速传感器抽油机异步电机的在线监测系统的软、硬件设计。论述了通过实时采集抽油机异步电机的三相电压和电流,计算电机的三相有功功率、无功功率和功率因数的方法。并利用电机模型参数,根据抽油机异步电机工作的特点,分析了实时计算电机定子磁链的幅值和相位的方法。同时提出了结合坐标变换下的定子电流计算,实时获取抽油机异步电机电磁转矩及转速的一般方法。     

高温超导发电讥的结构优化

为了降低高温超导发电机气隙磁密的谐波幅值,提高超导电机的稳定性。本文在Ansys基础上通过有限元电磁场计算并结合遗传算法对高温超导发电机屏蔽和励磁绕组的结构参数进行了优化,结果发现气隙磁密各次谐波幅值明显降低,气隙磁密波形得到明显改善。为了验证优化效果,本文利用时步有限元对优化前后电机模型进行空载电动势计算,发现空载谐波电动势幅值明显降低。最后本文分析了优化后励磁绕组磁场强度,进而分析了励磁绕组稳定性。     

高压电机线棒槽部防晕结构的研究

采用有限元计分析方法建立高压电机定子线棒槽部结构的三维模型,计算了槽部侧面垫条绝缘结构中的电场分布以及防晕层的面电阻率、气隙长度和线棒的额定电压等几种因素对防晕层上槽电位的影响。研究表明：防晕层上的最高电位与防晕层所用材料的电阻率和线棒的额定电压基本呈线性关系,较高的电阻率取值或较高的线棒电压会导致槽电位的升高;槽部侧面气隙轴向长度较小时,防晕层上的电位能够大幅度降低;对于特定型号的电机,选用对应特定的电阻率取值范围以及结构参数,是限制过高槽电位的产生,改善电机的绝缘性能的更好措施。     

基于EKF的异步电机直接转矩控制系统仿真研究

为了提高直接转矩控制(DTC)系统定子磁链估计精度,降低电流、电压测量的随机误差,提出了一种基于扩展卡尔曼滤波(EKF)实现异步电机转子位置和速度估计的方法.扩展卡尔曼滤波器是建立在基于旋转坐标系下由定子电流、电压、转子转速和其它电机参量所构成的电机模型上,将定子电流、定子磁链、转速和转子角位置作为状态变量,定子电压为输入变量,定子电流为输出变量,通过对磁链和转速的闭环控制提高定子磁链的估计精度,实现了异步电机的无速度传感器直接转矩控制策略,仿真结果验证了该方法的可行性,提高了直接转矩的控制性能.     

无刷直流电机槽极比对电机性能的影响

无刷直流电机的槽极比对高速无刷直流电机性能起着关键的作用。基于对电机槽极数比例的选择,对4极6槽、4极12槽和4极24槽的无刷直流电机进行设计和分析。由电磁负荷确定电机的主要尺寸和部分参数并建立数学模型。在有限元理论的基础上,利用Ansoft瞬态分析,对比几种电机的反电动势、气隙磁密、效率和转矩,验证了4极6槽电机的实用性以及在效率、转矩和气隙磁密方面的优势,最终得出该电机在理论和实践中各项性能都能达到最优效果的结论。     

电推进用48槽44极永磁容错电机低谐波分析与设计

分数槽集中绕组永磁电机由于具有高相间独立性的优点,非常适用于电推进系统。但是,其磁动势谐波大的弊端会严重影响电推进系统的性能。因此,进行永磁电机的低谐波设计,避免谐波引起过高的涡流损耗及振动噪声,具有十分重要的现实意义。文章分析了48槽44极永磁电机的磁动势谐波含量,通过有限元仿真验证多层绕组、定子不等齿宽、多层绕组相移、添加定子磁障等方法对绕组磁动势谐波的影响。实验表明,这些方法可以有效降低绕组磁动势的谐波含量。     

采用检测信号并考虑主磁链饱和的异步电机无传感器矢量控制

异步电机无速度传感器矢量控制需要通过由定子电压和电流建立的模型来计算磁链矢量和转速。如果磁链矢量的估计中存在误差，例如由电机模型参数不准确造成的误差，那么系统的稳定性就会出现问题。本文提出了一种考虑了主磁链饱和效应的方法来辨识磁链矢量甚至是在定子频率为零时的磁链。因此保证了全速和全转矩范围内的系统的稳定运行。     

异步电机定子磁链定向控制下的转矩控制鲁棒性

对异步电机定子磁链定向控制下的转矩控制鲁棒性进行了分析，在采用在线自校正电机定子电阻技术的情况下，仿真结果表明，即使转子时间常数变化了1～3.1倍，转矩闭环调节的鲁棒性表现良好。     

Novel permanent magnet motor drives for electric vehicles

Novel permanent magnet (PM) motor drives have been successfully developed to fulfil the special requirements for electric vehicles such as high power density, high efficiency, high starting torque, and high cruising speed. These PM motors are all brushless and consist of various types, namely rectangular-fed, sinusoidal-fed, surface-magnet, buried-magnet, and hybrid. The advent of novel motor configurations lies on the unique electromagnetic topology, including the concept of multipole magnetic circuit and full slot-pitch coil span arrangements, leading to a reduction in both magnetic yoke and copper, decoupling of each phase flux path, and hence an increase in both power density and efficiency. Moreover, with the use of fractional number of slots per pole per phase, the cogging torque can be eliminated. On the other hand, by employing the claw-type rotor structure and fixing an additional field winding as the inner stator, these PM hybrid motors can further provide excellent controllability and improve efficiency map. In the PM motors, by purposely making use of the transformer EMF to prevent the current regulator from saturation, a novel control approach is developed to allow for attaining high-speed constant-power operation which is particularly essential for electric vehicles during cruising. Their design philosophy, control strategy, theoretical analysis, computer simulation, experimental tests and application to electric vehicles are described     

Independent field-oriented control of two split-phase induction motors from a single six-phase inverter

Split-phase (six-phase) induction motor stator windings consist of two sets of three phase windings, which are spatially phase separated by 30 electrical degrees. Due to mutual cancellation of the air gap flux for all the 6n/spl plusmn/1 (n=1,3,5...) order harmonic voltages, called zero sequence components, large harmonic currents are generated in the stator phases. Only the 12n/spl plusmn/1 (n=0,1,2,3...)-order harmonic voltage components contribute toward the air gap flux and electromagnetic torque production in the machine. In this paper, a novel scheme is proposed where two six-phase induction motors are connected in series with proper phase sequence so that the zero sequence component voltages of one machine act as torque and flux producing components for the other. Thus, the two six-phase motors can be independently controlled from a single six-phase inverter. A vector control scheme for the dual motor drive is developed and experimentally verified in this paper.     

Flux observer with online tuning of stator and rotor resistancesfor induction motors

This paper proposes an adaptive flux observer for induction motors, where stator and rotor resistances are estimated in online environments. The variation of motor parameters during operation degrades the performance of the controller and the flux observer. Among the parameters of induction motors, rotor resistance is a crucial one for flux estimation, and stator resistance also becomes critical in the low-speed region. Under the persistent excitation condition, the proposed method estimates the actual values of stator and rotor resistances simultaneously, which guarantees the exact estimation of the rotor flux. The persistent excitation condition is not satisfied when the electric torque of an induction motor is absent due to the lack of rotor currents. Even in this case, the proposed method achieves the correct estimation of the rotor flux. Simulations and actual experiments show that the rotor flux is estimated in all operating conditions and that both resistances converge to their actual values when the electrical motor torque exists     

直接转矩控制全阶磁链观测器的设计及离散仿真

在交流异步机数学模型的基础上,建立异步电机直接转矩控制系统。对电机状态值和测量值之间偏差进行反馈校正,并把反馈校正项与估计磁链的电机数学模型结合起来,建立含有闭环状态估计的误差补偿器的全阶磁链观测器;利用Matlab／Simulink构建全阶磁链观测器,对构建的模型进行离散仿真,得到定子磁链的仿真波形,验证了全阶磁链观测器的正确性。     

Linear electric machines—A personal view

The history of linear motors is a history of shape. Once having departed from the cylindrical geometry of rotating machines, a wider world of three-dimensional design becomes possible. Linear induction motors dominate the field of linear drives to the same extent as does the rotary induction machine in relation to more complicated adjustable-speed motors. It is therefore thought appropriate to devote only one section to linear motors other than induction. A fairly full treatment of electromagnetic levitation is also included together with a treatment of oscillating machines. Perhaps the most important features are the division of electrical machines into two classes which are termed "magnetic" and "electromagnetic" and the "topological explosion" which is at present taking place in linear motor design. Some linear machines are already well established on a commercial basis but the vast bulk of recent inventions still remain to be exploited.     

Design of a plate type multi-DOF ultrasonic motor and its self-oscillation driving circuit

Multi-degrees-of-freedom (DOF) actuators have become more useful in the field of robotics, as a result of the increasing number of DOFs of systems. The general features of ultrasonic motors are suitable for constructing a direct-drive multi-DOF actuator. However, previously developed ultrasonic motors do not have advantages in volume and weight in contrast to multi-DOF motion units composed of plural electromagnetic motors. In the present study, authors developed a novel multi-DOF ultrasonic motor with a compact plate stator and spherical rotor. First, a new driving principle of the motor is proposed. Next, the stator geometry is designed in detail using the finite element method, and a prototype of the multi-DOF ultrasonic motor is produced. Then, vibration characteristics of the stator and driving characteristics of the motor have been measured, respectively. The results confirm that the motor successfully provides the desired multi-DOF motion of the rotor around orthogonal axes driven by a single plate stator. Finally, a novel self-oscillation driving circuit for the motor is proposed and driving tests using the circuit are conducted.     

Flux trapping in a ring-shaped YBCO bulk by pulsed fieldmagnetization

A pulsed magnetic field can be applied using small coils to generate a strong magnetic field for the magnetization of the high-Tc superconductors (HTS) to be used as quasi-permanent magnets in flywheels and motors. The dynamic electromagnetic behavior of two melt-processed ring-shaped Y-Ba-Cu-O bulks using the pulsed field magnetization (PFM) process has been experimentally investigated and analyzed. The flux trapped in the bulk by PFM process was compared to the flux trapped by field cooling process. Both cases then have been analyzed with a numerical model based on the finite-element method (FEM). The power-law model was utilized to relate the electric field to the current density inside the superconductor. The dependence of the critical current density on the magnetic field density was taken into account. Measured and calculated results are compared and discussed     

A Study of Influence of Configurations of the Windings on the Performance of Single Phase Induction Motor with Capacitor Start

The single phase induction motors needs two stator windings to produce rotating magnetic field : one main winding and the other auxiliary winding. The aim of the auxiliary winding is to create the rotating electromagnetic field when the machine is started-up and is afterwards turned off, generally through the centrifugal switch coupled together with the shaft of the machine rotor. The main purpose of this document is to evaluate the influence that the two windings have on the external characteristics of the single phase induction motor . For this purpose , two different kinds of windings were carried out and simulated, with the proposal to obtain some benefits. The main winding and the auxiliary winding were prepared and mounted on a prototype. The simulation was done via software based FEM , to make the extraction and results analysis possible. This results are shown at the end this document.