同步电动机状态方程

本文从abc坐标系统的同步电动机方程出发,通过线性变换,得到dqo坐标系统的同步电动机方程,根据我国广泛采用的同步电动机可控硅励磁系统列出微分方程,最后导出了同步电动机状态方程.     

反应式步进电动机动特性及其最佳控制

本文采用了近代控制理论常用的状态变量法研究了反应式步进电动机动特性及其最佳控制。在对步进电动机主要参数,进行了实验测定和分析基础上,考虑了各主要非线性因素,在电压方程中分别选取电流和磁链作状态变量,建立起状态空间数学模型。运用电子计算机,用四阶龙格——库塔法解非线性状态方程,计算了52BF三相反应式步进电动机单步、启动及加速等动态响应特性。进一步应用动态规划研究步进电动机最佳控制,以最短时问控制计算了52BF步进电动机最佳加速脉冲规律。最后,应用微处理机实现步进电动机最佳开环控制。 这项研究提高了步进电动机的快速性。     

径向励磁低速同步电动机的电路模型

用电势法建立了径向励磁低速同步电动机的电路模型,包括:电势方程、参数计算式和等效电路图.提出了同步后的这种电动机可等效于一台异步电动机的观点,在此基础上得到了电磁转矩及最大转矩的表达式,为分析和研究这种电动机奠定了基础.     

基于BP神经网络的非线性插值计算

基于ＢＰ神经网络的非线性插值计算①曹志彤（杭州大学物理系杭州３１００２８）以反应式步进电动机定子绕组的非线性电感为例,将插值节点作为学习样本集,采用ＢＰ神经网络模型模拟人脑神经元组织的信息处理机制,获取了反应式步进电动机定子绕组电感的非线性函数逼近的...     

稀土永磁同步电动机驱动抽油机的节能效益

传统的同步电动机与异步电动机相比具有突出的优点 ,如效率高、功率因数高 ,但是同步电动机仍然不能取代异步电动机用于小功率简单驱动场合 .电磁式的同步电动机需要附加起动控制装置而永磁同步电动机一般用于变频传动 .用于抽油机自起动的稀土永磁同步电动机是一种复合电机 ,它兼有同步电动机与异步电动机的优点 ,起动时如同异步电动机而牵入同步后运行在同步转速 .笔者研制的稀土永磁同步电动机转子上装有空间对称的鼠笼条和稀土磁铁 .抽油机负荷特点是驱动电动机需要起动转矩大而运行时负荷率很低 (30 % ) ,介绍了研制的稀土永磁同步电动机的结构和设计特点和节能机理 .油田现场试验结果表明驱动方案可行 ,用稀土永磁同步电动机替代三相异步电动机来驱动抽油机可节电 1 5%左右 .最后讨论了驱动电动机的优缺点和相应解决方法     

稀土永磁同步电动机驱动抽油机的节能效益

传统的同步电动机与异步电动机相比具有突出的优点,如效率高、功率因数高,但是同步电动机仍然不能取代异步电动机用于小功率简单驱动场合,电磁式的同步电动机需要附加起动控制装置而永磁同步电动机一般用于变频传动,用于抽油机自动动的稀土永磁同步电电动机是一种复合电机,它兼有同步电动机与异步电动机的优点,起动时如同异步电动机而牵入步后运行在同步转速,笔者研制的稀土永磁同步电动机转子上装有空间对称的鼠笼条和稀土磁     

逆变器非线性运行的同步电动机无源性控制研究

通过严格的理论分析和数学计算，建立了同步电动机在同步坐标系中E—L方程形式的数学模型，给出了磁场矢量控制的基本控制目标。以这些模型为基础，研究并设计了在负载转矩为任意时变未知情形下同步电动机时变转矩（转速、位置）的无源性渐近跟踪控制器。在实现机械控制目标的同时考虑并实现了对磁场方向和磁场幅值的控制，即同时实现了磁场矢量控制。     

永磁交流伺服精密驱动系统机电耦合动力学分析

对永磁交流伺服精密驱动系统进行动力学分析时,必须考虑系统的机电耦合影响.从机电能量转换的角度,根据系统的全局耦合分析和局部耦舍分析,建立了该系统全局耦合关系图和永磁同步电动机一精密传动装置子系统局部机电耦合关系图,然后采用拉格朗日一麦克斯韦方程建立了永磁同步电动机一精密传动装置子系统的物理模型和数学模型,推导了该子系统的动力学方程,并利用该模型进行了算例分析.结果表明,该模型是正确的,这为该系统的实验研究提供了理论依据.     

六相高速功率步进电动机

本文介绍六相三定子反应式功率步进电动机的结构型式,讨论了若干电磁设计以及结构设计和工艺问题,并提出了样机实测数据。     

变频电源供电永磁同步电动机数学模型与仿真

外贴式永磁同步电动机采用变频器供电,结构简单,控制方便。建了变频电源供电时永磁同步电动机的数学模型,对传统的机械运动方程进行了修正,使其更接近启动过程的实际情况。在此基础上,应用 MATLAB 语言编制了计算机仿真程序,用于分析电机不同工况时的瞬态性能和参数变化对动态性能的影响,并对一台 5.5 kW 的电机进行了仿真,结果证明修正后的数学模型是正确的。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that