异步电机定子绕组状态监测与故障诊断方法

定子绕组故障是异步电动机在运行过程中出现的主要故障,为了保障电动机的安全运行,对异步电动机进行状态监测与早期诊断是很有必要的。关于异步电动机定子绕组状态监测与故障诊断的方法,主要分为两类：第一类是基于模型的故障识别方法;第二类是基于信号检测的诊断方法。     

Influence of stator slotting on the synchronous performance of the hysteresis machine

The influence of stator slotting on the synchronous performance of a hysteresis machine is analyzed on the basis of a rectified model of its structure. The stator block holding the windings in equally spaced slots is replaced by a fictitious block of iron with finite permeability whose value is defined in two relevant directions, namely, the longitudinal and the radial. This set-up has a definite influence on the writing of the boundary conditions for the fields in the machine and consequently on machine behaviour. On the basis of the presented results, an optimization procedure can be attempted for achieving the best performance.     

异步电动机断相保护系统研究

本文主要阐述了电动机断相运行给电动机造成的危害,并在分析对比常用的三种电动机保护优缺点的基础上,介绍了一种简易的适用范围较广、灵敏度较高,且具有节电功能的三相异步电动机保护的原理。     

Winsock的异步模式探讨

讨论了使用Winsock实现异步通信的I/O模型的特点,通过分析比较,总结了各种I/O模型的适用情况,为应用开发提供了合理的建议。     

用HornetQ实现异步消息传输

在电子商务/电子政务的应用中,很多处理都需要以异步方式进行,JMS规范可以支持应用程序间消息的异步传递。详细论述了利用实现JMS规范的组件HornetQ来完成异步消息传输的过程。     

浅谈同班异步教学法

由于长期受应试教育的桎梏,教师在教学中大多注重优秀学生的培养和发展,以求完成升学目标。因而无暇顾及中等生,特别是差生的心理感受和课业成绩。在教学中无视学生智能的先天性差别和学习基础上的差别而采用＂一刀切＂、＂齐步走＂的教学方法,形成了优等生吃不饱,中等生吃得不太好,差生更是吃不了的怪现象。为此,笔者从2005年开始,在学校的配合下,对所教的班实施＂班内分组、同班异步＂教学。     

Electroosmotic flow hysteresis for dissimilar ionic solutions

Electroosmotic flow (EOF) with two or more fluids is commonly encountered in various microfluidics applications. However, no investigation has hitherto been conducted to investigate the hysteretic or flow direction-dependent behavior during the displacement flow of solutions with dissimilar ionic species. In this investigation, electroosmotic displacement flow involving dissimilar ionic solutions was studied experimentally through a current monitoring method and numerically through finite element simulations. The flow hysteresis can be characterized by the turning and displacement times; turning time refers to the abrupt gradient change of current-time curve while displacement time is the time for one solution to completely displace the other solution. Both experimental and simulation results illustrate that the turning and displacement times for a particular solution pair can be directional-dependent, indicating that the flow conditions in the microchannel are not the same in the two different flow directions. The mechanics of EOF hysteresis was elucidated through the theoretical model which includes the ionic mobility of each species, a major governing parameter. Two distinct mechanics have been identified as the causes for the EOF hysteresis involving dissimilar ionic solutions: the widening/sharpening effect of interfacial region between the two solutions and the difference in ion concentration distributions (and thus average zeta potentials) in different flow directions. The outcome of this investigation contributes to the fundamental understanding of flow behavior in microfluidic systems involving solution pair with dissimilar ionic species.     

异步电动机矢量控制特性研究

本文针对异步电动机变频调速原理,结合变频调速矢量控制策略,基于Matlab/Simulink工具箱,建立了异步电动机矢量控制变频调速系统仿真模型,对异步电动机的矢量控制特性进行研究。设置了多种电机运行状态,对电机的空载、加载、加速、减速等动态特性进行仿真研究,验证了所建立的仿真模型的正确性和可行性。     

高中历史异步教学法分析

我国一直以来都对教育发展十分重视,我国拥有悠久的历史,其中教育的发展也是源远流长,从远古最初的言传身教到封建社会的科举制度,再到如今现代化教育,我国教育事业一直呈上升状态。我国教育制度不断调整的最终目的就是为了培育出更加适应当下社会的人才。本篇论文就异步教学法在高中历史教育中的运用做浅要分析,并提出相应的见解提高教学质量。     

异步数字参考咨询与同步数字参考咨询服务模式的对比研究

对数字参考咨询服务的同步、异步、既可同步也可异步的各种具体服务模式的优点、缺点及适用范围作了详细的剖析;无人值守的用户自助的智能化系统是今后的一个方向;不同的图书情报机构应根据自身及用户的实际情况选择合适的参考咨询服务模式.     

基于CPLD的异步串行发送控制器

现有微控制器的串行口总数一般都很少,如常见的单片机只有一个或二个串口,在利用单片机进行应用系统设计时,往往需要进行串行口扩展。本文总结了目前常用的单片机串行口扩展技术,提出一种利用CPLD扩展单片机串口进行数据发送的方法,具有成本低、设计灵活、节省布线空间等特点。     

电力逆变器新型电流滞环控制方法研究

电力逆变器在电力行业中有着广泛的应用,在对电力逆变器控制方法进行系统研究的基础上,本文提出了一种适用于电力逆变器的电流滞环控制方法,其单个H桥采用与单极性SPWM调制相似的单极性电流滞环控制,脉冲产生简单,可以有效减少开关损耗。用类似相移SPWM脉冲产生方式来实现电流滞环控制时逆变器一相桥臂移相控制脉冲的产生。该控制方式保留了滞环电流控制响应速度快、具有内在限流能力和稳定性好等优点。通过仿真结果验证了本文所提方法的正确性。     

电动机常见异常现象及排除方法

文章详细列出了电动机各种异常现象及其解决办法,以保证电动机及传动设备的正常运行。     

A MD异步加载引擎设计与实现

采用一种改进的核心算法实现AMD异步加载引擎,该算法相对于传统的算法具有更强的可扩展性和可维护性。同时,基于AMD的核心算法框架实现其基本类库,并对AMD规范的利弊进行了分析。     

Asynchronous synchronization of complex networks with switched adjacent matrices

This note analyzes the synchronization problem for a class of complex networks. The considered network topology, symbolized by adjacent matrices, is assumed to be time-varying and subjected to a Markov process. When designing controllers to synchronize the network, we consider the asynchronous phenomenon occurred between the mode of the adjacent matrices and that of the controllers. A properly defined stochastic process, which is related to the Markov process by a conditional probability is then introduced to indicate the controller mode. Base on this connection, a sufficient condition is derived by using Lyapunov–Krasoviskii theorem to ensure the global synchronization of the considered complex network with a predefined noise attenuation level. The design scheme is presented by solving a series of LMIs. A numerical example is finally provided to verify the effectiveness of the proposed method.     

三相异步电动机常见故障的分析与处理

三相异步电动机得到越来越广泛的应用,如何及时正确分析、处理电动机的常见故障,对保证生产正常进行具有十分重要的意义。本文简要分析了三相异步电动机常见故障产生的原因,比较详实地叙述了排查故障的思路、方法,可供检修人员参考。     

异步传输网络的频域分块频谱估计算法

异步传输网络间通信信道组成复杂,对异步传输网络间通信信道的频谱的准确估计可以避免不占用多余的频带,能够实现高数据率通信。提出一种基于频域分块和脉冲响应的异步传输网络频谱估计算法。构建异步传输网络通信信道模型为缓慢时变、空变的相干多途信道,采用正交频率复用OFDM训练序列得到确定的起始帧概率分布,采用同步算法能有效减少系统子载波间的正交性抑制,得到系统函数的基本特征传递函数,实现对频域分块频谱估计。仿真结果表明,该算法能有效提高对频谱的估计精度,提高异步传输网络的通信性能,网络异步数据传输的吞吐量大幅提高。