异步电动机熔断器的选择、安装及其注意事项

异步电动机的熔断器作为负载电路的短路保护,应能及时地分断短路电流。因此熔断器选择适宜的额定电流是十分重要的,该电流不宜太大。为保证异步电动机能正常启动,熔断器的额定电流可依据电动机的额定电流、电动机的启动方式、启动时间、启动频度等情况合理确定。(1)在一台异步电动机的供电线路中,断路器的额定电     

鼠笼式转子与绕线式转子三相异步电动机传统启动方式对比分析与选择

本文对鼠笼式转子三相异步电动机与绕线式转子三相异步电动机传统启动方式下的启动原理进行了说明,并对两种转子三相异步电动机的在传统启动方式下的启动性能进行了深入的对比分析。给出了根据不同性质负载合理的选取三相异步电动机传统启动方法的理论依据。     

深槽型鼠笼式转子与普通型鼠笼式转子三相异步电动机启动性能对比分析

本文对深槽型鼠笼式转子三相异步电动机与普通型鼠笼式转子三相异步电动机的启动原理进行了阐述,并对两种鼠笼式转子三相异步电动机的启动性能进行了深入的对比分析,说明了深槽型鼠笼式转子三相异步电动机启动性能的优越性。     

电动机绕组修理与技术改造

一台舞台拉幕电动机的绕组每次重修后基本上只使 用一年多就烧坏了,最近只用了两次又烧了。据了解每次 都是启动绕组烧毁,而工作绕组却安然无恙。 1．工作原理与故障分析 该电动机是上海南洋电机厂生产的JZ7114型非标 准电阻启动式单相异步电动机。它由启动绕组和工作     

基于模糊控制的三相异步电动机软启动研究

三相异步电动机直接启动,存在较大的电流冲击,会引起电网电压下降,影响同一电网其他设备的正常运行。针对电动机的这一特性,介绍了一种基于模糊控制原理的三相异步电动机的软起动控制系统,通过在Simulink下建模、仿真,其结果证明了采用模糊控制的方法可以使三相异步电动机的启动电流减小,从而达到平稳起动的目的。     

基于PLC控制的异步电动机调速装置的设计与探讨

改革开放后,随着我国科技技术的快速发展,电子技术的不断更新换代,由PLC(可编程逻辑控制器)控制的变频异步电动机调控体系得到了越来越多的应用,基于PLC控制的异步电动机调速装置具有成本低、可靠性高、功能齐全等特点,在我国工业和农业生产中得到广泛应用,因此,设计PLC控制的异步电动机调速装置对实现电动机异步调速具有重要的实际意义,本文通过对变频器的探讨,对于PLC控制的异步电动机调速装置进行设计研究,具有一定的社会价值。     

三相异步电动机的二分频启动

<正> 三相异步电动机在实际运行过程中,总是需要启动和停止的。而异步电动机的启动方法,通常可以分为直接启动和降压启动两种。直接启动的主要缺点是启动电流很大,通常可以达到额定电流的4-7倍。启动电流大是因为启动瞬间转速n=0,转差率s=1,这时电动机的阻抗显著下降引起的。如果电网的容量相对电动机而言不是很大,则电动机的启动电流就会引起电网电压的降落,从而影响其他电动机或用电设备的正常工作,这种情况就不允许直接启动。     

数据驱动技术在多电机同步系统中的应用

随着异步电动机在电机驱动系统中应用范围的逐步拓宽,多电机控制系统建模过程中需要处理的非线性问题更加明显,而且难度明显增加。通过使用局域模型的模糊辨识方法,在数据的聚类处理基础上,构建针对多台异步电动机的控制系统建模方法,能够较好地处理多台异步电机控制过程中的非线性问题。从控制系统的仿真效果来看,这种控制方法能够实现异步电机的同步控制,且控制效果良好。     

煤矿大功率防爆异步电动机软启动技术研究

针对煤矿大功率防爆异步电动机的启动特性需求,提出一种基于数字信号处理器的软启动控制方案,解决起动过程电流过大、能耗高的问题。在分析软启动技术和煤矿大功率防爆异步电动机启动过程上,从软启动器的电气结构出发,设计基于TMS320F2812A的数字式控制系统,实现电动机起动过程端子电压、电流和输出转矩的调节。     

各种交流电动机的旋转原理

目前较常用的交流电动机有两种:(1)三相异步电动机。(2)单相交流电动机。第一种多用在工业上,而第二种多用在民用电器上。一、三相异步电动机的旋转原理三相异步电动机要旋转起来的先决条件是具有一个旋转磁场,三相异步电动机的定子绕组就是用来产生旋转磁场的。我们知道,三相电源相与相之间的电压     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

Teleportation of an arbitrary unknown N-qubit entangled state under the controlling of M controllers

A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers(M < N) is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home-Zeilinger (GHZ) state and N-M non-maximally entangled Einstein-Podolsky-Rosen (EPR) pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it.     

Diode-end-pumped Nd:YVO4/LBO lasers with 4.2W continuous-wave output at 457 nm

A continuous-wave (CW) 457 nm blue laser operating at the power of 4.2 W is demonstrated by using a fiber coupled laser diode module pumped Nd: YVO4 and using LBO as the intra-cavity SHG crystal With the optimization of laser cavity and crystal parameters, the laser operates at a very high efficiency. When the pumping power is about 31 W, the output at 457nm reaches 4.2 W, and the optical to optical conversion efficiency is about 13.5% accordingly. The stability of the out putpower is better than 1.2% for 8 h continuously working.     

A rigorous proof of MIMO channel capacity’s increase with antenna number

It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output（MIMO） communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.     

Call for Papers

正Wireless Body-area Networks The last decade has witnessed the convergence of three giant worlds:electronics,computer science and telecommunications.The next decade should follow this convergence in most of our activities with the generalization of sensor networks.In particular with the progress in medicine,people live longer and the aging of population will push the development of wireless personal networks