外磁路涡流对铁氧体开关响应时间的影响

从开关电路和响应磁场2个方面对涡流的影响进行了研究.以激励线圈等效阻抗的变化,得出涡流效应对外磁路开关电路响应时间的影响;在响应磁场方面,以典型模的方式,应用安培定律、楞次定律、电磁感应方程,以数学推导得出典型模涡流对响应磁场的影响,以此得出涡流对外磁路开关响应时间的影响因素及其量级大小.通过具体产品的设计验证,证明了结论的正确.     

场路结合法求解永磁同步电动机磁路系数

永磁同步电动机由于采用永磁体励磁替代了电励磁,增加了转子磁路的复杂性,使得采用等效磁路法求取空载漏磁系数、计算极弧系数、气隙系数等磁路系数时,难以获得较为准确的结果。提出了运用场路结合法求解永磁同步电动机磁路系数的思路,利用等效磁路法对磁路系数进行理论分析,并将电磁场有限元仿真的结果代入到等效磁路法定义的相关公式中,求得磁路系数较为准确的数值,提高了电磁计算的精度。     

电磁超声表面波产生机理的ANSYS仿真

针对电磁超声在金属表面缺陷检测的应用问题,研究了电磁超声表面波的产生和传播机理,根据电磁超声产生原理,采用有限元仿真分析软件ANSYS,对电磁超声表面波的产生过程进行了偏置磁场、工件表面感生涡流和所受洛伦兹力、振动产生超声波三部分的仿真.仿真结果表明通有交变的线圈在工件感生出交变的涡流,在偏置磁场的作用下,工件表面质点受到与激励电流和感生涡流频率相同的洛伦兹力,在这个力的作用下,质点发生位移,并以表面波的形式向外传播.     

变压器等效电路获取的教学方法

变压器是典型的电磁耦合器件,其等效电路获取是教学的重点内容。传统方法是基于变压器内部电磁关系和绕组折算获得T型等效电路,本文提出了一种新的获取等效电路的教学方法。笔者先通过物理过程分析获取电路和磁路耦合模型,然后通过深入分析磁路中磁通、磁势和磁导关系并引入相关电流分量,逐步用无源电路元件等效替代漏电势源和激磁电流源,而完全电磁耦合部分则用理想变压器替代,最后利用理想变压器的变换特性获得T型等效电路。教学分析过程概念明确又结合学生本身具有的电路和磁路基础知识,在此基础上再分析绕组折算原理可以起到事半功倍的教学效果。     

电磁轴承定子磁极不同拓扑结构的磁场分析

当电磁轴承设计有容错要求时,往往采用磁极独立驱动的方案,磁极的拓扑结构体现更加复杂多样化.本文以8极结构独立驱动的径向电磁轴承为研究对象,对电磁轴承定转子本体模型进行网格剖分,以变分原理和分片差值为基础的数值分析,来确定网格内各点的矢量磁位,得到了不同拓扑结构(全N(S)型、NSNS型和NNSS型)下,电磁轴承定转子磁...     

电机统一电磁耦合模型研究

等效电路是"电机学"课程教材中各类电机的重要内容,但教材着力于不同电机结构,因此存在各种不同的等效电路。本文利用磁场和材料特性不变原则,通过坐标变换和绕组折算,将不同频率的电压方程转换成相同频率和统一磁链形式,再引入磁势与统一匝数乘积的新物理量AT2,将磁势与磁通描述的磁路模型转换成AT2与磁链模型,从而获得统一电磁耦合模型。理论研究揭示了不同种类电机之间存在的共同电磁耦合本质,将有助于深入理解《电机学》教材的内容。     

基于解析模型的永磁同步电机优化设计

永磁同步电机的电磁转矩和涡流损耗是两个重要指标,在体积等限制条件下,有效提高电磁转矩并降低转子涡流损耗是电机设计的关键。针对这个问题,文中采用解析法,分别计算电磁转矩和涡流损耗,并采用粒子群优化算法,对电机尺寸参数进行优化设计。解析模型包括电枢反应磁场和空载磁场模型。在计算涡流损耗时考虑涡流反应、永磁体周向分段等,优化算法的目标函数并使用权值将多目标转换成单目标。通过解析解与时步有限元数值解的对比可看出,解析解的误差在2%左右。参数影响分析的响应面显示,在定子绕组节距为25°时,电磁转矩和涡流损耗相关性一致。优化迭代结果显示,优化设计降低了76%的平均涡流损耗、22%的平均电磁转矩和68%的电磁转矩波动。     

电磁型微马达的微转子研究

简要介绍了直径２ｍｍ电磁型微马达的结构和磁路。对微转子的设计和加工,多微磁极的写（充）入和均匀性进行分析和讨论。测量了不同充磁条件下的微转子剩余磁化强度和微转子之间的吸力。     

恒定磁场分数匝开关变电装置

本文所述装置用于长距离磁路传输电能系统中,长距离磁路是指距离在400 km以上的闭合磁路。长距离磁路通常采用恒定磁场,而恒定磁场取电方法,包括变磁阻的方法或变电路的方法进行感应取电,本文针对变电路的方法所涉及的恒定磁场分数匝开关变电装置进行了分析,为实施长距离磁路输电提供理论支持。     

基于STM32的磁悬浮轴承数字控制器设计

针对传统磁悬浮轴承转子系统开环不稳定、非线性和强耦合等特性,需要对电磁力施加主动控制才能使转子稳定悬浮的缺陷,本文设计了一种基于STM32的磁悬浮轴承数字控制器方案。该控制器以ARM STM32F407ZGT6微处理器为核心,设计了电源转换、电涡流位移传感器、功率放大器控制、实时时钟以及声光报警等硬件电路;同时编写了基于国产嵌入式实时操作系统RT-Thread的多线程软件框架,实现了数据采集、PID算法等功能。实验结果表明,该数字控制器下的磁悬浮轴承转子系统可以在200ms内达到稳定悬浮状态,运行可靠、实时性好、速度快、抗干扰能力强。     

Design and control of active magnetic bearing system with Lorentz force-type axial actuator

As the size of five-axes active magnetic bearing (AMB) system gets smaller, the space limitation for installation of axial magnetic bearing unit and the eddy current induced braking of radial magnetic bearing unit become a stringent design concern. In this paper, a new type of compact, high-performance five-axes AMB with solid cores and rotor is proposed, which consists of four permanent magnets, four U-shaped cores and 16 control coils. It features that the radial and axial magnetic bearing units are integrated for compact design and that the homo-polar type configuration of poles with optimized pitch length is adopted to minimize the eddy current induced braking force. The proposed homo-polar AMB system is levitated by the Lorentz-type axial as well as Maxwell-type radial forces. Based on the magnetic flux distribution analysis, the control algorithm is designed to account for the coupled effect between the radial and axial control fluxes. Experiments are also carried out with a prototype AMB system to validate the new design concept.     

Offset-Free Model Predictive Control for a cone-shaped active magnetic bearing system

Active Magnetic Bearings (AMB) are mechatronic systems that support a rotating shaft using magnetic levitation. The standard AMB architecture includes two radial actuators and one for the axial direction. An alternative geometry with cone-shaped magnetic cores allows for a more compact layout without a dedicated axial actuator. However, this configuration reduces the axial force generation capability and requires a more complex control architecture due to the inherent coupling of the axial and radial control actions. When using decentralized control, effective handling of the coil current limitations together with the axial disturbance rejection is difficult to achieve. In this context, the present paper demonstrates the benefits of applying Offset-Free Model Predictive Control (OF-MPC) for a cone-shaped AMB system. A procedure for the overall design is presented and supported by the experimental work conducted in a scaled machine that reproduces an on-board turbo-compressor unit for an aircraft. The modeling of the system is described together with the design of the OF-MPC in all its parts: general control architecture, disturbance model and observer design, target calculation and control problem formulation. An OF-MPC variant with reduced control horizon is proposed and implemented in real time. Experimental results demonstrate that the prototype is compliant with application-specific stability requirements from the ISO 14839-3:2006 standard. In addition, experiments show that OF-MPC outperforms decentralized PID controllers in terms of axial disturbance rejection. OF-MPC yields a favorable constrained optimal control technique for cone-shaped AMBs because intrinsic coupling and current saturation are optimally handled by the controller.     

考虑微磁芯磁阻的分布参数微梁执行器小信号宏模型

以多级弯曲磁微梁执行器为研究对象，先采用梁的模态函数线性组合来逼近梁的变形曲线，然后利用磁路定律，考虑了在宏观磁执行器中忽略的磁芯磁阻，建立了考虑力-磁耦合的非线性方程组，克服了以往的磁微执行器模型不能考虑力磁耦合，而且忽略磁芯磁阻的缺点．计算结果与实验数据及有限元计算结果对比表明，文中的模型有足够的精度，可以作为宏模型使用．     

多级弯曲磁微梁执行器力-磁耦合宏模型

本文以多级弯曲磁微梁执行器为研究对象,先采用梁的模态函数线性组合来逼近梁的变形曲线,再将求模态磁场力的积分项分段求积,最后利用磁路定律,建立了考虑力磁耦合的非线性方程组,克服了以往的模型不能考虑力磁耦合的缺点.方程组的复杂程度(阶数)与所取的模态阶数相关.计算结果同实验数据对比表明,模型有足够的精度,可以作为宏模型使用.     

交变磁场传感器法拉第屏蔽的研究

为了更有效的接收所需信号,我们除了进一步提高传感器本身的性能外,还要消除一些不必要的干扰.在检测低频交变磁场而且磁场信号极其微弱时,首先要选用高性能的交变磁场传感器将交变磁场信号转换为电信号,然后采用一系列的选频放大等电子技术,这样在两者之间就会产生不必要的电场耦合,影响对有用信号的准确测量,为了阻断该电场耦合,对交变磁场传感器采用法拉第屏蔽是不可或缺的重要环节.     

Identification of bearing dynamic parameters and unbalance states in a flexible rotor system fully levitated on active magnetic bearings

An identification algorithm for the estimation of dynamic parameters of Active Magnetic Bearings (AMBs) and rotor residual unbalances has been presented for a flexible rotor system. The proposed algorithm is suitable for the state of the art rotors that are fully levitated on AMBs. Due to a partial attenuation of unbalance responses by AMBs, difficulty arises in getting the correct estimations from unbalance responses alone, which is not the case with the conventional bearings. For latter bearings responses do reflect real effects of unbalances. Thus, the present algorithm is based both on the measured AMB controlling currents and rotor unbalance responses, and uses these to identify AMB dynamic parameters of each AMB and residual unbalances in flexible rotors at predefined balancing planes. The algorithm is based on the least-squares fit technique in frequency domain. AMB dynamic parameters consist of the force–displacement and the force–current coefficients in two orthogonal transverse directions for each AMB. The finite element method has been used to obtain a unified model of the flexible rotor fully levitated with AMBs for the numerical study, in which the PID controller is used. Numerical simulations have been performed to illustrate the reliability of proposed algorithm. The algorithm is also tested against the measurement noise and modelling errors to investigate its robustness. The proposed algorithm has been finally applied to an experimental data (from Technical University of Darmstadt, Germany) from a fully levitated five-disc flexible rotor test rig with the help of two AMBs. Estimates of AMB dynamic parameters are found to be in close range with that of theoretical values.     

HF RFID Reader Antenna with Loop Switch for Avoiding Magnetic Coupling

This paper studies the magnetic coupling between two adjacent loop antennas that are parallel to each other in a plane and presents a new practical method to avoid the resulting magnetic coupling interference. The study focuses on the high frequency radio‐frequency identification (RFID) system for casino applications, where several loop antennas are closely built into a game table to monitor gaming chips. In this case, neighboring loop antennas may severely interfere with each other by magnetic coupling, which leads to the malfunction of the RFID system. In this paper, we present a practical loop antenna with a new loop switch circuit for avoiding magnetic coupling. The loop switch circuit is integrated with a matching circuit and automatically operated by using an interrogating signal from a reader. We verified the validity of the proposed design by showing that an RFID reader with the proposed antenna can exactly and separately read the gaming chips placed on the different betting zones of a game table.