长定子直线感应电机饱和特性和非线性计算

提出了一种应用于电磁发射场合的新型无槽双边长定子直线感应电机,该电机取消了传统电机的齿槽结构,增大了电机定子绕组的导电面积,降低了电机损耗和温升。基于电磁场有限元仿真计算得到了电机定子漏感和励磁电感的饱和特性,给出了电机非线性工况的计算方法。实验结果和计算结果的比较验证了计算方法的正确性。     

感应电机定子温度场的数值计算

针对中小型感应电机结构复杂热模型难以建立的问题,以一台小型感应电机为例,采用有限元方法,建立了电机的二维温度场数值计算模型。给出了定子二维温度场计算的泛函以及相关热性能参数的计算方法;计算了不同负载运行时样机定子的稳态温度场。计算结果与实测值的比较,验证了所采用计算模型及方法的合理性。该电机温度场计算模型可以应用到其他同类电机定子温度场的计算与分析。在该温度场计算模型的基础上,分析比较了机壳散热翅高度的变化对电机定子温度场的影响,研究了气隙温度对定子温度场的影响。     

网络拓扑法在潜油电机温度场计算中的应用

应用网络拓扑法对潜油电机的温度场进行了分析和计算,并结合潜油电机提出了具体的处理方法。应用结果表明,这种方法简便易行,计算精度较高,适用于中小型电机的温升计算。     

BSG电机的散热仿真分析

采用逆向工程对某进口电机进行了逆向建模,基于流体力学、传热学基本理论,考虑电机不同零部件热源的差异性以及电机运转时流体流场和温度场的复杂分布,采用有限元数值计算方法,对该电机整机温度场进行了仿真计算。通过与实验数据对比,计算误差均在0.4%内,验证了所建数值模型和采用计算方法的准确性,随后对电机内部零部件温度分布进行了分析研究。该数值模拟方法为电机温度场分析提供了简捷高效的计算方法,从而提高了电机性能的优化效率、促进国外产品的国产化。     

用三维有限元法计算直线电机的起动推力

用二维有限元法计算直线电机的推力目前已得到了比较广泛的应用,但在计算大气隙直线电机的磁场分布时,二维方法尚有较大的局限性。本文作者在计算用于浮法玻璃生产的直线电机起动推力时,根据电机的设计结构特点,提出了三维有限元计算的数学物理模型和计算方法,并在不同的电流相位时进行了实例计算。计算结果与实验值较为一致。     

皮带机直驱永磁电机设计和温度场计算

针对皮带机用直驱永磁电机存在的温升过高的问题,对皮带机直驱永磁电机的电磁设计、计算模型、损耗计算、温度场计算等方面进行了研究。利用ANSYS软件对永磁电机绕组铜耗、铁心损耗和涡流损耗进行计算,设计了电机水冷系统,通过Fluent对永磁电机三维模型进行稳态温升计算,获得了电机关键部分的温度场分布,最后进行样机的温升实验。研究结果表明,采用场路耦合方法能够准确计算电机损耗,采用三维稳态温度场仿真所得数据与样机实验数据吻合良好,求解方法正确,可为直驱电机的设计提供一定的参考。     

高压湿式潜水电机转子三维温度场分析

为了更准确地研究高压湿式潜水电机的温度场分布情况,以3150kW、6kv高压潜水电机为例进行分析。建立了潜水电机转子三维温度场的物理模型和计算模型。考虑潜水电机冷却系统的特殊性,转子散热表面采用分段的方法加载散热系数。以电磁计算得到的损耗为热源,利用有限元软件对电机进行了温度场计算,并将计算结果与实测测量值和采用传统方法施加散热系数得到的温度场进行了比较,验证了该方法的准确性,为利用有限元法求解电机温度场时散热系数的加载提供了新的方法。     

万家寨引黄工程大泵电机的研制

对万家寨引黄工程GM3泵站6500kW大泵电机的研制情况进行了详细分析。主要介绍了电机的电磁、结构、刚强度计算和通风计算等部分。通过对此电机的研制,熟悉并掌握了此类电机的设计和分析计算方法,为同类型电机的设计提供了一些有益的参考。     

YKK系列中型高压电机起动特性的计算

为了准确计算YKK系列中型高压电机的起动特性和起动时间以确定电机起动过程对电机本身和电网产生的影响,在M-T坐标系下建立了三相感应电动机的动态数学模型,并对电机起动特性的计算方法进行了改进.结合电机所带实际负载数据,对新型YKK系列电机的起动特性和起动时间进行了计算,分析了降压起动对电机产生的影响.计算结果表明:得到的...     

纳米精度运动台电机伺服参数校准方法研究

多自由度纳米精度工件台的精度直接受电机力常数和增益平衡矩阵的影响,需要进行周期性测试。因实际电机负载与理论计算负载有差异且随时间发生改变,导致其电机力常数变化,直接采用理论计算负载会降低工件台精度。采用传递函数计算电机实际负载,建立电机负载与电机力常数间的关系,实现了电机力常数的校准。引入串扰系数描述不同电机轴间的串扰,并提出了增益平衡矩阵的详细计算方法。实验验证了该方法的正确性,并实现了工件台10 nm的定位精度。     

Practical method for generation expansion planning based on dynamic programming

This paper presents an efficient method which provides the optimal generation mix and the optimal generation construction process. The approximation method in which the dynamic programming technique and gradient method are combined is applied to determine the optimal generation mix with hydropower generation technologies. The successive approximations dynamic programming (SADP) technique, which is very suitable for high-dimensional multistage decision process problems, is used for obtaining the optimal generation construction process. The effectiveness and feasibility of the developed technique are demonstrated on a practical power system model which has five types of generation technologies including a hydropower generation technology.     

Tachycardia control with cardiac pacemakers

Techniques used to treat tachyarrhythmias with brief electrical impulses are described. The disease process is described, identifying the prevention of one of the three conditions required for reentry (which provides the mechanism for most electrically convertible rhythms) as the basis for therapy. The risk of inducing fibrillation is discussed. The four major pacing techniques used to treat tachycardia are described. The first technique involves using additional pacemaker pulses to establish the appropriate conditions permitting interruption of the tachycardia. The second technique, which permits adaptation to the variations in tachycardia characteristics, is scanning. Scanning changes the intervals on successive bursts in an interactive process, allowing a series of paced intervals to be tested. The third technique is usually called an adaptive or automatic technique. The final technique is ramp pacing, which allows extrastimuli to be introduced at progressively premature intervals within a burst of stimuli.     

Numerical calculation of the terahertz field-induced changes in theoptical absorption in quantum wells

In the presence of a strong terahertz field, the optical (i.e., valence-to-conduction band) transitions in semiconductors occur between states which are altered by the terahertz field. This alteration has a direct impact on the optical absorption. We describe a numerical technique for calculating the optical absorption in this case by solving the Schrodinger equation for the electron-hole envelope function in real space. This technique correctly accounts for the Coulomb interaction between optically created electron-hole pairs and nonperturbative terahertz-field induced alteration of the states. We applied this technique to investigate the optical absorption of quantum wells of finite width in which terahertz/optical mixing can be significant and which cannot be treated analytically     

基于虚拟仪器技术的电路板信号检测系统

为了帮助维修人员快速检查、定位电路板故障,提高电路板维修的效率,本文提出以虚拟仪器技术为平台,结合CPLD技术、数据库技术和USB总线技术应用于电路板信号检测。能够在脱机条件下产生电路板工作所需要的各种输入信号,同时可以测试电路板输出的信号,并将正确波形进行存储,用以作后续处理。经过实际使用,系统运转正常,达到了设计要求。     

A novel adaptive HBCC technique for three-phase shunt APF

This paper proposes an important improvement of the hysteresis band current control (HBCC) technique for three-phase shunt active power filter (APF) to eliminate harmonics and to compensate the reactive power generated by three-phase rectifier. In this technique, a simple and quick prediction of the hysteresis band is added to a phase-locked-loop (PLL) control to ensure constant switching frequency and synchronization of modulation pulses independently on system parameters. This allows the advantages of quick response, good current tracking accuracy and minimal ripple in three-phase systems. This technique is robust and it is characterized by the simplicity, this aspect is very significant for a practice realization because it constitutes the factors which determine the cost and the reliability of industrial assembly. The proposed technique determines the switching signals of the three-phase shunt APF and the algorithm which is based on the dc bus capacitors voltage regulation using proportional-integral (PI) controller is used to determine the suitable current reference signals. The behavior of the proposed technique has been fully verified by digital simulation, where the obtained results show that the proposed technique can improve shunt APF performances noticeably.     

A contactless technique for determining the average sizes of erosion-hazardous droplets in polydisperse wet steam flow

A new combined numerical and experimental technique for determining the average sizes of droplets contained in wet steam flows is presented, central to which is the use of laser diagnostic systems. Basic aspects relating to implementation of the technique under static conditions on an experimental steam dynamic setup are considered. Primary results obtained from approbation of the technique for a wet steam flow moving in a narrowing flat nozzle are presented.     

基于GSM网络的火灾报警网络监控器的设计

本文设计了一种基于GSM网络的远程火灾报警网络监控器。并给出了网络监控器的工作原理及软、硬件设计和功能实现。新的基于GSM网络的远程火灾报警网络监控器主要是为了弥补传统的基于PTSN网络的远程火灾报警网络监控器的不足,提高网络监控器运行的可靠性和独立性。通过实际工程应用表明,这种以无线GSM网络传输技术为基础的远程火灾报警网络监控器,为火灾远程报警提供了一种实用的联网技术方案,对城市火灾报警网络的发展起到了推动和促进作用。     

载波调换调制技术在级联多电平SAPF中的应用

电容电压不平衡是影响级联H桥多电平并联有源电力滤波器(SAPF)安全可靠运行的关键问题。通过分析载波相移调制技术(CPS-SPWM)对直流侧电容电压的影响,提出了一种基于控制直流侧电容电压平衡的载波调换调制技术,确立了双电压环与电流环结合的三闭环SAPF控制策略。这种调制方式算法简单、易实现,能在较小开关频率下实现较好的补偿效果的同时,有效地解决级联H桥多电平SAPF直流侧电压平衡问题。仿真和实验证明,该载波调换调制技术是有效、实用的,能对直流侧电容电压平衡起到良好的控制效果。     

Adaptive non-communication protection for power lines BO scheme3-The accelerated operation approach

This paper presents the accelerated operation scheme of the adaptive noncommunication protection technique for power lines with complex configurations, such as multi-end feeders and ring mains. In the scheme, the overcurrent directional relays are arranged in two operating modes, the fixed time operation and accelerated operation. The relays with faster operating time in the conventional time grading coordination remain unchanged. The new technique is employed to enable accelerated operation to be achieved for the relays which are in the positions for which slow operating time is set when using conventional time grading technique. For a fault occurring on the protected system, the relays of fixed time operation mode will operate at the preset time for the fault within its protected direction. The relays which are programmed to use accelerated operation mode will determine whether a fault is on the protected section or not by using the BO technique, that is to detect the circuit breaker operation by determining whether the line section is in a balanced operation condition or not. The relay makes accelerated tripping decisions for a fault on its protected section. Simulation studies of the responses to various system and fault conditions show that the scheme can significantly increase the speed of the relay responses in the protection of power line systems with complex configurations     

多电平逆变器PWM控制方法的研究

近年来,多电平逆变器在大功率场合应用越来越广泛.基于空间矢量原理提出了一种新的多电平PWM控制方法,这种PWM方法称为多电平最优空间矢量PWM方法(MOSV PWM),可用于多电平串联逆变器供电的压频比控制的异步电动机调速系统.仿真结果表明,MOSV PWM方法与多电平载波方法和单脉冲法相比有许多优点,可以在线实现,输出线电压THD低,开关频率低.这种方法可以推广用于其它类型的多电平逆变器,除电机传动外还可以用于静态无功补偿和其它FACTS场合.