电气工程及其自动化专业英语

电气工程及其自动化专业教研室电气工程及其自动化专业教研室 电气工程及其自动化专业英语电气工程及其自动化专业英语 Specialized English for Electrical Engineering ＆ Its Automation 戴文进戴文进 主主 编编 杨植新杨植新 副主编副主编电气工程及其自动化专业教研室电气工程及其自动化专业教研室Part 2 Electric Machinery •Unit 11 The Transformer on No Load •Unit 13 Construction and Application of D.C. Machines •Unit 16 Three-Phase Induction (Asynchronous) Machine with the Rotor at Standstill· •Unit 19 Armature Reaction of Salient-Pole Synchronous Machine a Two-Reaction Theory 电气工程及其自动化专业教研室电气工程及其自动化专业教研室Unit 11 The Transformer on No Load-Specialized English Words•in close proximity (to) 紧密耦合 •permeability 磁导率 •magnetizing current 激磁电流 •power component of current 电流的有功分量 •sinusoidal variations 正弦变量 •a mutually induced e.m.f. 互感电动势•the applied voltage 外施电压•zero-power-factor 零功率因数•the no-load power factor 空载功率因数•formulate 用公式表示,系统地阐述•saturation 饱和电气工程及其自动化专业教研室电气工程及其自动化专业教研室Unit 11 The Transformer on No Load•The Simple Two-Coil Transformer The transformer is a straightforward application of Faraday's Law of Electromagnetic Induction. The simple transformer consists of two coils in close proximity. One coil of N1 turns is excited with alternating current and therefore establishes a flux φ11 which alternates with the current (随时间交变随时间交变）. The other coil is linked by （与与---交链交链）most of this flux and thus has a mutually induced e.m.f. of value e2=－N2dφ21/dt. This e.m.f. would drive a load current through any circuit connected to the terminals of the second coil. Energy would then be transferred through the medium of the magnetic field（磁场媒介磁场媒介） from coil 1 to coil 2. 电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The transformation could be from any convenient input voltage to any convenient output voltage. • This apparently simple function of the transformer makes it as vital to modern industry as the gear train which, as a “transformer” of speed and torque represents an interesting analogy（句子的主语是句子的主语是“function”，谓语为谓语为“make”，“as vital…as”意为意为“与与……一样重要一样重要”，，“which”引导一个定语引导一个定语从句从句“which represents an interesting analogy as a‘transformer’of speed and torque”，修饰修饰“gear train”，意为意为“齿轮箱与变压器表齿轮箱与变压器表现出一种有趣的相似，齿轮箱被称为速度和转矩的现出一种有趣的相似，齿轮箱被称为速度和转矩的‘变换器变换器’。

•The coils would be on an iron core (铁芯铁芯）and so at the cost of introducing iron losses, the value of flux per ampere is increased several hundred times because of the change of permeability from μ0 to μ0μ r . 电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The exciting or magnetizing current （励磁电流励磁电流）can thus be very small. Further, the proportion of the total flux which is linked mutually by the two coils is greatly increased. •Looked at another way, the leakage flux Φ 1 which links N1 turns alone and “leaks” between the two windings without linking the N2 turns, is a much smaller fraction of the total, making for(有助于有助于,倾向于倾向于) more efficient energy transfer.•The mutual flux would be a much larger percentage of the total and the flux pattern (磁力线图磁力线图)would be rather more involved(复杂的复杂的), but simplified diagrams of this kind are quite adequate for the understanding of the principles to be discussed in this chapter.•The exciting coil which initiates (激励激励)the flux changes is called the primary winding, and the coupled coil which receives energy as a result (因此因此), is called the secondary winding.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•It should not be difficult to realize that the two functions are interchangeable: if coil 2 were excited instead, a mutual e.m.f. would be induced in coil 1 which would then become the secondary winding(二次绕组二次绕组). •It should be obvious that since the primary winding also experiences flux changes, there is a primary e.m.f. self-induced this time. With winding 1 excited, the primary e.m.f. would be equal to N1dΦ 11/dt. This is practically in phase opposition to (与与---反相反相)the applied terminal voltage V1 and limits the current to a very much smaller value than V1/R1, where R1 is the primary resistance(原边电阻原边电阻). •As explained later, the resistance drop is normally very small so that the back e.m.f. is virtually equal in magnitude to V1.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•If the applied voltage is alternating sinusoidally at frequency f=ω/2π Hz, a vector diagram can be drawn, and for an air-core transformer, neglecting resistance. As shown I1 is the magnetizing current producingΦ 11 which rises and falls with it in time phase. It is therefore in quadrature with (与与---正交正交)V1 and the circuit is a zero-power-factor lagging load. With the secondary circuit open, the primary coil is an inductor whose voltage drop is +N1dΦ 11/dt or in vector form=jω L11I1.•The two components of flux linking N1 (与与N1交链的磁通交链的磁通)are shown and though I1 is in phase with both of them,it will be found that when the secondary is carrying current, the mutual flux is no longer in phase with the primary current due to the reaction of the secondary ampere-turns(磁势磁势).电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The phase of componentΦ 1 is unchanged, however, since it is produced by primary current alone and is therefore in phase with it. Further, even with an iron core the reluctance offered to Φ 1 is still predominantly due to its path in air so that the leakage flux remains virtually proportional to the primary current providing(=provided) the iron path is not greatly saturated(饱和饱和). The e.m.f. －N1dΦ 1/dt may thus be treated as if it were due to an unsaturated inductance of magnitude N12∧1. The corresponding leakage reactance is a dominant factor in transformer behavior(characteristic).•For the iron-cored transformer which will form the subject of this chapter, the total back e.m.f. of the primary, －N1dΦ 11/dt, will be considered in two components, the one due to leakage and the other due to the mutual flux(互感磁通互感磁通).电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The first one will normally be treated in terms of the voltage drop required to sustain the current. This is equal to +N1dΦ 1/dt, or vectorially for frequency f it is given by jω L1I1 =jX1I1which is a voltage leading the current by 90°(领先电流领先电流90度度). The second component is due to the mutual flux and is represented by a vector E1, lagging 90°behind the flux (滞后磁通滞后磁通90度度)time vector. This too could be treated as a voltage drop jωMI1N1/N2=jXmI1=－E1, but the mutual flux is in iron, subject to permeability changes and so the mutual inductance M varies with the flux level.•Here is the vector diagram for an iron-cored transformer with its secondary winding open circuited, the no-load condition. Allowance has been made for the iron losses (对铁耗损进行补偿对铁耗损进行补偿)which require a power component of current Ip.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•This is drawn in phase with －E1, the component of applied voltage necessary to sustain +E1. E1Ip is the iron loss in watts. The ampere-turns required to produce the flux are given by ImN1 so that on no load the primary takes a current I0 which is made up of the two components Im and Ip. In practice Ip is very much smaller than Im and the no-load power factor is very low. The mutual flux is shown asΦm and is equal toΦ21 on no load. •When the secondary carries current, I1 increases from I0;Φm is then due to the combined effect of primary and secondary ampere-turns, but is little changed fromΦ21. Consequently the magnetizing and power requirements of the flux are nearly constant so that I0 can be regarded as a substantially constant component of I1 at any load.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•It will be noticed from the diagram that since the e.m.f.s E1 and E2 are due to the same flux Φm, the voltage ratio E1/E2 is the same as the turns ratio N1/N2. •In fact, on no load （空载时空载时）, the impedance drops I0R1 and I0X1 are so small that V1 is virtually the same magnitude as E1 and the turns ratio is equal to the no-load voltage ratio V 1/E2. •Thus any voltage V 1 can be transformed to (变换成变换成）any other voltage E2 by suitable choice of primary and secondary turns（（通过适当的选择原副边匝数）通过适当的选择原副边匝数）. On load（负载时负载时）, the voltage at the secondary terminals V 2 is measurably（obviously） different from （显著地不同于显著地不同于）E2 .电气工程及其自动化专业教研室电气工程及其自动化专业教研室The Circuit Equation for the Transformer on No Load• From the vector diagram, and in accordance with circuit principle, we have Further, it shows the current split into components in phase and in quadrature with －E1. The quadrature component Im flows through a pure reactance Xm and the in-phase component Ip flows through a pure resistance rm, thus giving the correct voltage/current phase relationships. This figure can therefore be used to represent the transformer on no load; it is an equivalent circuit for this condition. The value of the magnetizing reactance xm depends on the saturation level(饱和程度饱和程度). The voltage drop across it is －E1=jxmIm and it has already been pointed out that M is not constant with flux.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•However, the normal operation of power transformers is at constant voltage and frequency so the peak value of fluxΦm’ is substantially unchanged with load. A value of xm corresponds to the average slope(斜率斜率) of the flux /current curve. The equivalent circuit could then be regarded as having constant parameters, the values being determined by calculation or by test.•It should be stressed here that any techniques described in the book which attempt to get a linear equivalent for a non-linear saturated circuit are inevitably deficient (imperfect) in some respects (在某些方面在某些方面) and cannot be used to (用来用来)draw general conclusions(得出一般的结论得出一般的结论). •Though suitable for dealing with particular aspects of a problem involving saturation(饱和问题饱和问题), they are neither unique (only one of its kind) nor universal solutions.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•It is important to realize the relative magnitudes of the various voltages in the circuit. A transformer is so designed that a mutual flux, sufficient to produce a voltage equal to that of the supply V1 is reached without undue saturation(没有过度饱和没有过度饱和). The high permeability of the magnetic circuit under these conditions, together with other design considerations, result in a no-load leakage impedance drop which is negligible by comparison with E1. •The voltage drop vectors have thus been greatly exaggerated in order to demonstrate their phase relationship clearly and in practice, X1 may be very much larger than R. 电气工程及其自动化专业教研室电气工程及其自动化专业教研室•when the transformer is fully loaded (额定运行额定运行)and the primary current increases from I to twentyfold or more, the voltage drop in the primary leakage impedance may be perhaps 3% of V1 in the normal transformer. Even then, however, flux will be little changed from the no-load condition. Im and Ip in turn are substantially (largely) constant with load.The Transformer E.M.F. EquationThe induced . due to mutual flux, -NdΦm/dt, is conveniently formulated in a different way to deal with the special case of sinusoidal variations. The instantaneous value of flux may then be expressed as:  Φm= Φm sinωt电气工程及其自动化专业教研室电气工程及其自动化专业教研室•where Φm is the maximum value reached in the cycle. The induced e.m.f. is thus e= -NdΦm/dt=-ωN Φm cosωt which is another sine wave lagging Φm by 90°. The peak value of this e.m.f. is 2πfNΦm .since ω =2πf and the r(root).m(mean).s(square)(有效值有效值). value is•Applying above equation to the two coils:—the primary e.m.f. due to mutual flux=4.44 fN1 Φm =E1 ;—the secondary e.m.f. due to mutual flux =4.44 fN2 Φm =E2Note: in each case (在每种情况下在每种情况下)that the maximum value of mutual flux must be used. There are the flux and the two e.m.f. waves in a relationship already demonstrated vectorially(用矢量表示的用矢量表示的).电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The instantaneous value e2 is shown in phase with e1 since this corresponds to its relationship with Φm .• With the coils wound round the core in the same direction, the top ends must be positive at the same instant since if the secondary circuit were closed, e2 would drive a current whose magnetic action would oppose the flux change by producing the induced current. This is in accordance with (符合符合)Lenz’s law. •The terminal marking A1 and a1 indicate cophasal potential variations. Obviously, the phase of e2 relative to the external secondary circuit could be reversed by crossing over (交换交换）the connections. The applied voltage V1 is shown equal and opposite to e1 which is virtually true on no load.电气工程及其自动化专业教研室电气工程及其自动化专业教研室3词量的变化词量的变化•[1] 增词增词: 即增加原文中虽无其形但有其意的词汇即增加原文中虽无其形但有其意的词汇,或从词汇或从词汇要求要求,语法要求语法要求,逻辑要求和修辞要求等几个方面来考虑逻辑要求和修辞要求等几个方面来考虑. Electronics is the science of the electrons 电子学是电子学是研究研究电子的电子的一门一门科学科学. Having a lot of advantages, this imported foreign DC machine will eventually be displaced by home-made one. 尽管尽管这台国外进口直流电机有很多优点这台国外进口直流电机有很多优点,但它总有一天会但它总有一天会被国产直流电机取代被国产直流电机取代. It will be seen that the processes above involve a change in either the magnitude or the direction of the current of the surge arrester。

能够预见能够预见，上述过程不是涉及，上述过程不是涉及避雷针避雷针电流大小的变化，就电流大小的变化，就是涉及其方向的是涉及其方向的变化变化．．. 电气工程及其自动化专业教研室电气工程及其自动化专业教研室•[2]重复重复 It is called classical one if control theory is based on input-output relationships；modern one if control theory is based on direct use of the differential equations themselves 如果控制理论是基于输入输出关系如果控制理论是基于输入输出关系,叫做古典控制理论叫做古典控制理论,如果如果控制理论是基于直接使用微分方程本身控制理论是基于直接使用微分方程本身,则叫做现代则叫做现代控制理论控制理论. Can you roughly give the static and dynamic characteristics about this power supply apparatus？ 你能大致给出这个电源装置的静态你能大致给出这个电源装置的静态特性特性和动态特性吗和动态特性吗?•[3]减词减词 In the past，to fly to the moon was out of the question。

过去飞往月球是不可能的事情过去飞往月球是不可能的事情. In these days，to fly to the moon is out of question 现在飞往月球是不成问题的现在飞往月球是不成问题的.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The TV sets produced by our factory are good in quality and low in price. 我厂生产的电视机物美价廉我厂生产的电视机物美价廉. The paper on computer control technology is thought of considerable value for reference. 这篇有关计算机控制技术的论文被认为有相当大的这篇有关计算机控制技术的论文被认为有相当大的参考价值参考价值. Because heat does not take up any room and it does not weigh anything, it is not material. 热不占有任何空间热不占有任何空间,也没有什么重量也没有什么重量,因此它不是物质因此它不是物质. There are two kinds of new theories at present, neural network and wavelet ones, which are used in signal processing. 目前有两种新理论目前有两种新理论,即神经网络理论和小波理论即神经网络理论和小波理论,它们都能用它们都能用于信号处理于信号处理.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•end shield （电机定子的）端盖（电机定子的）端盖•terminal box 出线盒出线盒 cast steel 铸钢铸钢•film of vanish 漆膜漆膜 wedge 槽楔槽楔•silicon controlled rectifiers (SCRs)可控硅整流器可控硅整流器•cumulatively compounded self-excited machine 积复励自励积复励自励电机电机•brush holder 刷把刷把 cast iron 生铁生铁•ferromagnetic 铁磁性的铁磁性的 oxide coating 氧化层氧化层•centrifugal force 离心力离心力•cut-and-dried 不大会改变的，固定模式的不大会改变的，固定模式的Unit 13 Construction and Application of D.C. Machines电气工程及其自动化专业教研室电气工程及其自动化专业教研室Unit 13 Construction and Principle of D.C. Machines•Construction of D.C. Machines• A D.C. machine is made up of two basic components:•—The stator which is the stationary part of the machine. It consists of the following elements: a yoke （轭部轭部）inside a frame; excitation poles and winding; commutating poles（换向极换向极） (compoles) and winding; end shield （端盖端盖）with ball or sliding bearings（滑动轴承滑动轴承）; brushes and brush holders（刷握刷握）; the terminal box（接线盒接线盒）.•—The rotor which is the moving part of the machine. It is made up of a core mounted on the machine shaft（轴）. This core has uniformly (均匀地均匀地）spaced slots into which the armature winding （电枢绕组电枢绕组）is fitted. A commutator（换向器换向器）, and often a fan, are also located on the machine shaft.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The frame（机座机座） is fixed to the floor by means of a bedplate and bolts. On low-power machines the frame and yoke are one and the same components, through which the magnetic flux produced by the excitation poles （磁极产生的磁通磁极产生的磁通）closes（闭合）. The frame and the yoke are built of cast iron or cast steel or sometimes from welded steel plates（焊接钢板焊接钢板）. •～1mm) laminated iron sheets（硅钢叠片）。

硅钢叠片） The yoke is usually mounted inside a non-ferromagnetic （非铁磁非铁磁）frame (usually made of aluminum alloys, to keep down the weight). •To either side of the frame there are bolted two end shields, which contain the ball or sliding bearings. 电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The (main) excitation poles are built from～1mm iron sheets held together by riveted bolts. The poles are fixed into the frame by means of bolts. They support the windings carrying the excitation current.•On the rotor side, at the end of the pole core is the so-called pole-shoe which is meant to facilitate a given distribution of the magnetic flux through the air gap. The winding is placed inside an insulated core mounted on the frame（安装在机座上的铁心）（安装在机座上的铁心）, and secured by the pole-shoe.•The excitation windings（励磁绕组励磁绕组） are made of insulated round or rectangular （矩形矩形）conductors, and are connected either in series or in parallel. 电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The windings are linked in such a way that the magnetic flux of one pole crossing the air gap is directed from the pole-shoe towards the armature (north pole), and the flux of the next pole is directed from the armature to the pole-shoe (south pole).•The commutating poles, like the main poles, consist of a core ending in the pole-shoe and a winding wound round the core. They are located on the symmetry (neutral) axis between two main poles, and bolted on the yoke. Commutating poles are built either of cast-iron or iron sheets.•The windings of the commutating poles are also made from insulated round or rectangular conductors. They are connected either in series or in parallel and carry the machine‘s main current（armature current）.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The rotor core is built of～1mm silicon-alloy sheets. The sheets are insulated from one another by a thin film of varnish or by an oxide coating～0.05mm thick. The purpose is to ensure a reduction of the eddy currents （涡流涡流）which arise in the core when it rotates inside the magnetic field. These currents cause energy losses which turn into heat. In solid cores（实心铁芯）（实心铁芯）, these losses could become very high, reducing machine efficiency and producing intense（过多的过多的） heating.•The rotor core consists of a few packets of metal sheet. Redial or axial cooling ducts （径向或轴向通风道径向或轴向通风道）(8～10mm inside) are inserted between the packets to give better cooling. •Pressure is exerted（施加施加） to both sides of the core by pressing devices fixed on to the shaft（固定在轴上的压力装置）（固定在轴上的压力装置）.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The length of the rotor usually exceeds that of the poles by 2～5mm on either side—the effect being to minimize the variations in magnetic permeability caused by axial armature displacement（由电由电枢转子轴向偏移引起的枢转子轴向偏移引起的）. The periphery（圆周圆周） of the rotor is provided with teeth and slots into which the armature winding is inserted.•The rotor winding consists either of coils （which is）wound directly in the rotor slots by means of specially designed machines or coils already formed（成形线圈）成形线圈）. The winding is carefully insulated, and it secured within the slots by means of wedges (槽楔槽楔) made of wood or other insulating material.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The winding overcharge（伸出部分伸出部分） are bent over （弯曲弯曲）and tied to one another with steel wire （用钢线绑扎在一起用钢线绑扎在一起）in order to resist the deformation which could be caused by the centrifugal force（由离心力引起的变形由离心力引起的变形）.•The coil-junctions （线圈出线端线圈出线端）of the rotor winding are connected to the commutator mounted on the armature shaft. The commutator is cylinder made of small copper segments insulated from one another（彼此绝缘的铜片）彼此绝缘的铜片）, and also from the clamping elements by a layer of micanite（通过一层云母与夹紧元件绝缘通过一层云母与夹紧元件绝缘）. The end of the rotor coil are soldered（焊接焊接） to each segment•On low-power machines, the commutator segments form a single unit, insulated from one another by means of a synthetic resin （合成树脂）such as bakelite（酚醛树脂）.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•To link the armature winding to the fixed machine terminals, a set of carbon brushes slide on the commutator surface by means of brush holders. The brushes contact the commutator segments with a constant pressure （以一定的压力以一定的压力）ensured by a spring and lever（弹簧和刷杆）（弹簧和刷杆）. Clamps mounted on the end shields support the brush holders.•The brushes are connected electrically—with the odd-numbered （奇数奇数）brushes connected to one terminal of the machine and the even-numbered （偶数）brushes to the other. The brushes are equally spaced round the periphery of the commutator （沿换向沿换向器圆周均匀地分布器圆周均匀地分布）—the number of rows （排数）of brushes being equal to the number of excitation poles.电气工程及其自动化专业教研室电气工程及其自动化专业教研室Application of D.C. Machines•With the advent of controlled rectifiers of various kinds, the importance of D.C. generators has subsided （消退）somewhat since it is cheaper to convert to D.C. with a transformer and rectifier rather than with an A.C. motor and D.C. generator（用变用变压器和整流器而不用交流电动机和直流发电机）压器和整流器而不用交流电动机和直流发电机）. The rectifier performance is inferior in terms of power factor, simplicity of control, regenerative and reversing ability and harmonic generation, but score on cost, in most cases, space, noise and maintainance; the latter considerations weighing more heavily （更具重要性更具重要性）in a modern age. •D.C. generators will continue to be made for their virtues but will lose certain traditional fields of application（应用场合应用场合）. They are invaluable for use as dynamometers（测力计测力计） coupled mechanically to engines （发动机发动机）and motors of various kinds to control and measure the output. 电气工程及其自动化专业教研室电气工程及其自动化专业教研室•By mounting the stator in bearings so that the torque （转矩）（转矩）reaction can be exerted against a spring balance(弹簧称弹簧称）, the torque output can be read off directly. Generators are also useful for imparting （给予给予）special characteristics to a load in a simple manner, e.g. automatic current limitation for D.C. welding generators utilizing series windings and exaggerating armature reaction demagnetizing effects （电枢反应去磁效果电枢反应去磁效果）.•As far as motors are concerned, there are continual attempts to obtain infinitely variable speed motors which can be directly connected to the A.C. mains and thus dispense with （免除免除）the intermediate A.C./D.C.—conversion apparatus. A recent development involves the substitution of controlled rectifiers for the commutator（用可控整流器代替换向器用可控整流器代替换向器）.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•Since the commutator and brushes act to direct the coil currents （将线圈中电流变为直流将线圈中电流变为直流）in a particular sense（判断判断） when the coil is related to a particular position in the field systems, this function can be performed by an external reversing circuit actuated by shaft-position sensing devices（用安装在轴上的传感器装置（用安装在轴上的传感器装置来触发）来触发）.• Tappings （接线头接线头）from the armature winding, which could not be on the stator, are brought out to this circuit. Some success has been achieved with these various methods but there are always disadvantages and it seems likely that the demand for D.C. motors will continue for many years to come. 电气工程及其自动化专业教研室电气工程及其自动化专业教研室•Shunt, compound and separately-excited motors are used for drive which have to operate over a wide range of speeds and in automatic control systems. Series motors are used when heavy starting torques and overloads are characteristic automatically limits （机械特性的限制机械特性的限制）and power demand and gives a high torque per ampere on overload.•Summarizing （总结，概括总结，概括）then, the D.C. motor can be used for practically any application though it has a lower limit on maximum power and maximum speed than the synchronous（同步同步） and induction motors（感应电动机感应电动机）.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•Discussion of D.C. machine applications involves recapitulation（扼要说明扼要说明） of the highlights of the machine‘s performance features（电机的重要性能电机的重要性能）, together with economic and technical evaluation of the machine’s position with respect to competing energy-conversion devices. For D.C. machines in general, the outstanding（salient） advantage lies in their flexibility and versatility（灵活多样灵活多样）.• The principal disadvantage （主要缺点主要缺点）is likely to be the initial investment concerned. Yet the advantages of D.C. motors are such that they retain a strong competitive position （有力的竞争位置有力的竞争位置）for industrial applications.•D.C. generators are the obvious answer to the problem of converting mechanical energy into electric energy in D.C. form（将机械能转换成直流电能将机械能转换成直流电能）.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•When the consumer of electric energy is geographically removed from the site of energy conversion by any appreciable distance（当当电力用户远离发电区域电力用户远离发电区域）, however, the advantages of A.C. generation, voltage transformation, and transmission are such that energy conversion and transmission in A.C. form are almost always adopted（差不多采用交流发电和交流传输差不多采用交流发电和交流传输）, A.C.-to-D.C. transformation take place at or near the consumer．• •The D.C. generator as part of an A.C.-to-D.C. motor-generator set （交流交流-直流电动机发电机组直流电动机发电机组）must compete with semiconductor rectifier systems. When large-power rectification from A.C. to constant-voltage D.C. form is involved, the electronic methods usually offer determining economic advantages. 电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The principal applications of D.C. generators, therefore, are to cases where the primary energy conversion occurs very near the point of consumption and cases where the ability to control output voltage in a prescribed manner is necessary, although solid-state（固态固态） controlled rectification using silicon controlled rectifiers （可控硅可控硅整流器整流器）(SCRs) and Triacs（双向可控硅双向可控硅） is finding widespread application（得到了广泛的应用）得到了广泛的应用）.•Among D.C. generators themselves, separately excited (他励他励）and cumulatively compounded self-excited machines are the most common. Separately excited generators have the advantage of permitting a wide range of output voltages, whereas self-excited machines may produce unstable voltage in the lower ranges, where the field-resistance line becomes essentially tangent to the magnetization curve（与磁化曲线相切与磁化曲线相切）.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•Cumulatively compounded generators may produce a substantially flat voltage characteristic or one which rises with load, whereas shunt or separately excited generators (assuming no series field in the latter, which, of course, is not at all a practical restriction) produce a drooping voltage characteristic （下降的电压特性下降的电压特性） unless external regulating means are added（除非采用外部调整措除非采用外部调整措施施）. •So far as the control potentialities of D.C. generators are concerned, the control-type generators represent the results of a fuller exploration （充分研究充分研究）of the inherent possibilities.•Among D.C. motors, the outstanding characteristics of each type are as follows. The series motor operates with a decidedly drooping speed as load is added, the no-load speed usually being prohibitively high（非常高非常高）; 电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The torque is proportional to almost the square of the current at low saturations and to some power （幂幂）between 1 and 2 （电流的电流的1-2次方成正比次方成正比）as saturation increases（随着饱和随着饱和程度增加程度增加）.•The shunt motor at constant field current（励磁电流励磁电流） operates at a slightly drooping but almost constant speed as load is added, the torque being almost proportional to armature current; equally important, however, is the fact that its speed can be controlled over wide ranges by shunt-field control, armature-voltage control, or a combination of both.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•Depending on the relative strengths of shunt and series field, the cumulatively compounded motor is intermediate between （介介于于---之间之间）the other two and may be given essentially the advantages of one or the other.•By virtue of （由于由于）its ability to handle heavy torque overloads while cushioning（保护保护） the associated power overload with a speed drop, and by virtue of its ability to withstand severe starting duties, the series motor is best adapted to hoist（升降机升降机）, crane（起重机起重机）, and traction-type (牵引牵引类类）loads. Its ability is almost unrivaled in this respect（在这在这方面的能力是方面的能力是无敌的无敌的）. •Speed changes are usually achieved by armature-resistance control.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•In some instances（在某些情况下）在某些情况下）, the wound-rotor induction motor with rotor-resistance control competes with （与与---相媲美相媲美）the series motor, but the principal argument concerns the availability and economics of a D.C. power supply （电源电源）rather than （而不而不是是）inherent motor characteristics.•Compound motors with a heavy series field have performance features approaching those of series motors except that （除了除了）the shunt field limits the no-load speed to safe values; the general remarks for series motors therefore apply（适用适用）. •Compound motors with lighter series windings do not infrequently（罕见地罕见地） find competition from （对抗对抗）squirrel-cage induction motors with high-resistance rotors ---- so-called high-slip motors（高滑差电动机高滑差电动机）.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•Both motors provide a definitely（有限的有限的） drooping speed-load characteristic such as is desirable, for example, when flywheels （飞飞轮轮）are used as load equalizers（平衡器平衡器） to smooth out （平稳平稳）intermittent load peaks（间歇性负载峰值间歇性负载峰值）. Complete economic comparison of the two competing types must reflect both the usually higher initial cost of a compound-motor installation and the usually higher cost of losses in the high-slip induction motor.•Because of the comparative simplicity, cheapness, and ruggedness of the squirrel-cage induction motor, the shunt motor is not in a favorable competitive position for constant-speed service except at low speeds, where it becomes difficult and expensive to build high-performance induction motors with the equal number of poles.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The comparison at these low speeds is often likely to be between synchronous and . The outstanding feature（突出的特征突出的特征） of the shunt motor is its adaptability to adjustable-speed service（应用于应用于调速场合调速场合）, by means of armature-resistance control for speeds below the full-field speeds（基于额定转速以下基于额定转速以下）, field-rheostat（磁场变阻器磁场变阻器） control for speeds above the full-field speed, and armature-voltage control for speeds below (and, at times, somewhat above) the normal-voltage full-field speed. •The combination of armature-voltage control and shunt-field control, together with the possibility of additional field windings in either the motor or the associated generator to provide desirable inherent characteristics, gives the D.C. drives an enviable degree （令人惊叹令人惊叹（羡慕）的程度（羡慕）的程度）of flexibility（多样性多样性）.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The use of solid-state motor drives reinforces（巩固了巩固了） the competitive position of D.C. machines where （=in which）complete control of operation is important.•It should be emphasized that （应该强调的是应该强调的是）the choice of equipment for a significant engineering application to adjustable-speed drives （应用于调速驱动的重大工程应用于调速驱动的重大工程） is rarely a cut-and-dried matter （已经决定的事情，已成定局的事情已经决定的事情，已成定局的事情）or one to be decided from a mere verbal list of advantages and disadvantages （只根据口述列举出优点和缺点就能决定的事只根据口述列举出优点和缺点就能决定的事情情）. In general, specific（确切的确切的）, quantitative, economic and technical comparison of all possibilities should be undertaken. Consideration must be given to （必须考虑必须考虑）the transient-and dynamic-response（瞬态和动态响应瞬态和动态响应）. 电气工程及其自动化专业教研室电气工程及其自动化专业教研室•Local conditions （局部条件局部条件）and the characteristics of the driven equipment (e.g. constant-horsepower（恒功率恒功率）, constant-torque（恒转矩恒转矩）, variable-horsepower and variable-torque requirements) invariably （总是总是）play an important role. •One should also remember that comparative studies （比较和研究比较和研究）of motor cost and characteristics are based on the combination of motor and control equipment, for（因为因为） the latter plays an important part in determining motor performance under specific conditions（特定条件下特定条件下） and represents a by no means （决不决不是是）negligible portion of the total initial cost. •Control equipment coupled with susceptibility to control （结合对结合对控制的灵活性控制的灵活性）makes D.C. machines the versatile（多用途的多用途的） energy-conversion devices that they are.电气工程及其自动化专业教研室电气工程及其自动化专业教研室4 词序变动词序变动•[1] 多个单个词汇都作前置定语多个单个词汇都作前置定语 China is becoming a modern powerful socialist country 中国正在成为一个社会主义的现代化强国中国正在成为一个社会主义的现代化强国.•[2] 多个单个副词作状语多个单个副词作状语 英语中多个单个副词都做状语修饰动词或全句时英语中多个单个副词都做状语修饰动词或全句时,分别分别可放在句首可放在句首,动词之前动词之前,助动词或动词之后助动词或动词之后,或放在句中或放在句中,或连或连在一起也或分开使用在一起也或分开使用. He always studied theory of circuit hard these days.•[3]复合词复合词 iron and steel industry 钢铁工业钢铁工业 Back and forth 前后前后 Rich and poor 贫富贫富电气工程及其自动化专业教研室电气工程及其自动化专业教研室5 词性转换词性转换•英语中名词使用较多，动词使用较少，英语中名词使用较多，动词使用较少，一个简单句中只一个简单句中只有一个谓语动词，其他动词应该是动词的非谓语形式．有一个谓语动词，其他动词应该是动词的非谓语形式．而汉而汉语中动词使用较多，而且英语中一词多义，一词多类现象极语中动词使用较多，而且英语中一词多义，一词多类现象极为普遍，因此，翻译时词类不能对等．为普遍，因此，翻译时词类不能对等． The robot is capable of learning to perform an industrial task and then of being left to perform it tirelessly 机器人机器人能能学会做工学会做工,然后能不停地工作下去然后能不停地工作下去. The top rotates about its axis. 陀螺围陀螺围绕绕着其轴线旋转着其轴线旋转. He is into systems identification. 他是他是搞搞系统辨识的系统辨识的.电气工程及其自动化专业教研室电气工程及其自动化专业教研室 Communication satellites have found application in international live transmission of important events. 通信卫星已经用来实况通信卫星已经用来实况转播转播国际间的重要事件国际间的重要事件. The adoption of this new device will greatly down the harmonic content of voltages and currents. 采用采用这个新装置可大大降低电压和电流中的谐波含量这个新装置可大大降低电压和电流中的谐波含量. Are you familiar with the drawbacks of this type of operational amplifier. 你你熟悉熟悉这尖运算放大器弊端吗这尖运算放大器弊端吗? Laser acts differently from light from common sources. 激光激光的作用的作用与普通光源发出的光不同与普通光源发出的光不同. The resonant in a linear circuit means that the terminal voltage and current are in phase. 线性电路中谐振线性电路中谐振的意思的意思就是端电压与电流同相位就是端电压与电流同相位.电气工程及其自动化专业教研室电气工程及其自动化专业教研室Unit 16 Three-Phase Induction (Asynchronous) Machine with the Rotor at Standstill •active current component 有功电流分量有功电流分量•the first harmonic . 基波磁势基波磁势•high-order harmonic . 高次谐波磁势高次谐波磁势•reactive current component 无功电流分量无功电流分量•symmetrical 对称的对称的 asymmetrical 不不对称的对称的•reluctance 磁阻磁阻 reactance 电抗电抗•distributed windings 分布绕组分布绕组•concentrated windings 集中绕组集中绕组•number of pole pairs 极对数极对数•be referred to 折算到折算到•number of slots per pole and phase每极每相槽数每极每相槽数电气工程及其自动化专业教研室电气工程及其自动化专业教研室Unit 16 Three-Phase Induction (Asynchronous) Machine with the Rotor at Standstill•The object of this chapter is to show that, with the rotor at standstill, an induction machine operates as a transformer, differing from a conventional transformer only in design (distributed windings 分布分布绕组绕组on the rotor and the stator, presence of air gap, etc. ).• As to (对于对于）the physical nature of the phenomena, it is the same in both cases. It is expedient（方便的方便的）, therefore, to begin the study of induction machines, as in the case of transformers, with the consideration of （考虑考虑）the limiting operating conditions of the machine, i.e. the no-load and short-circuit conditions and then, in the following chapter, extend the concept of the induction machine as a transformer to the case of a machine with the rotor in rotation。

电气工程及其自动化专业教研室电气工程及其自动化专业教研室•In further discussions, we shall consider a three-phase induction machine with slip rings （带滑环的电机带滑环的电机-绕线式感应电机绕线式感应电机）and a rotor which may be switched open（开路开路）, short-circuited（短短路路）, or closed through a resistance（通过电阻闭合通过电阻闭合）. •We shall consider all variables（变量变量） to be （认为是认为是）sine-wave functions of time and space, the role（action） of the upper order harmonics （高次谐波高次谐波）to be separately studied later. •The voltages, and currents are given by their effective values （有有效值效值）, the and fluxes by their maximum values. •The winding phases are assumed symmetrical （假定各相绕组是假定各相绕组是对称的对称的）.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•Assume that the rotor circuit of an induction machine is open, the rotor at standstill （省略省略is ）, and the stator connected to a circuit with a voltage U1 and frequency f1.•In this case the induction machine represents a transformer on no-load. The primary is the stator of the machine and the secondary—the stationary rotor. •Correspondingly, all values pertaining to the stator （所有关所有关于定子的值于定子的值）will be called primary and denoted by “1”, and all values pertaining to the rotor will be called secondary and denoted by “2”.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The course of reasoning in the given case is, in principle, the same as for the transformers. Under the action of the voltage U1, a no-load current I0 flows through the stator winding.•The . F1 created by this current gives rise to a flux, one part of which Φm is linked with the windings of both parts of the machine, while the other part, Φσ1, is linked only with （仅与仅与---交链交链）the stator winding. The first flux is the main（mutual flux）, and the second is the leakage flux. •If p is the number of pole pairs （极对数）（极对数）of the machine, then the speed n1 of the . F1 and the corresponding （相应的相应的）flux Φm will be n1 = 60f1 /p（r/min）电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The main flux Φm creates in the stator and rotor windings the E1 and E2, determined by the formulas：•The leakage flux Φσ1 creates in the stator winding a leakage . Eσ1 for which•where x1 is the leakage reactance （漏抗漏抗）of the stator winding.电气工程及其自动化专业教研室电气工程及其自动化专业教研室 In addition, the stator winding has an active resistance （有功电阻有功电阻）r1, taking into account its action in the form of a voltage drop I0r1, we may write the primary . equation of an induction machine in the same way as for transformers.It should be recalled that in this equation E1 and I 0Z1 are components of voltage U 1 ,each of which is in equilibrium with the corresponding .To the identical equations of the primary for a transformer and the induction machine correspond 与与---一致一致 also the essentially identical no-load diagrams。

全句结构实际应是全句结构实际应是“For a transformer and the induction machine，the essentially identical no-load diagrams correspond to the identical equations of the primary e.m.f.s.”.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•Therefore, we shall not give the diagram for the second time. But , quantitatively, there is a noticeable difference between the two diagrams. Indeed, the induction machine has a relatively large air gap. Owing to this, current I0 in induction machines usually amounts to 20%~50% of the rated current IN , , it is considerably larger than the no-load current of the transformer(3%～10% of IN ). •Besides, the winding resistance in induction machine is also relatively larger than in transformers. The voltage drop in the stator winding of the induction machine on no-load therefore constitutes 2%～5% of the rated voltage （额定电压）（额定电压）of the machine, whereas in transformer it does not generally exceed 0.1%～0.4% of the latter.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The no-load currents of a three-phase induction machine constitute a symmetrical system, since the reluctances of all paths of the three-phase fluxes are the same. On the other hand, the wave shape of the no-load current is close to a sine wave, since in the presence of a relatively large air gap the third harmonic of the current or, correspondingly, of the flux cannot be of any appreciable importance.•The . transformation factor of an induction machine, ke representing the ratio E1/E2 is•In induction machines, as in transformers , the secondary is referred to （折算到折算到）the primary, , the real secondary winding is replaced by another number of slots per pole and phase as the primary （与原与原边相同的每相每极槽数边相同的每相每极槽数）.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The secondary parameters are then to be duly recalculated in order to retain the real power relationships in the machine. The . of the referred secondary E2’ is E2’=keE2=E1•With the rotor open-circuited and stationary, the only losses in the machine are the stator copper losses m1I02r1 where m1 is the number of stator phases, and the stator and rotor iron losses （仅仅有的损耗是定子铜耗和定子转子铁耗有的损耗是定子铜耗和定子转子铁耗）pst1+ pst2. These losses are covered by （补偿补偿）the power P10 consumed by the machine from the power circuit. Thus P10 = m1I02r1 + pst1+ pst2电气工程及其自动化专业教研室电气工程及其自动化专业教研室•Since the current I0 and resistance r1 are relatively great in induction machines, the copper losses Pcop1 make up a considerable part （占占了了---的相当大部分的相当大部分）of the power P10, whereas in transformers we may always disregard them.•Knowing P10, we can determine the active current component （有有功电流分量功电流分量）I0a from the formula（根据公式根据公式）.•The active current component I0a is generally small in comparison with the reactive component (无功分量无功分量)I0r of this current, and the angleθ is equal toθ=70°~80°.•The equivalent circuit of an induction machine on no-load does not differ in any way from the corresponding transformer circuit.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•If with the rotor braked (转子堵转转子堵转)(n=0) we move the sliding contact of the rheostat (变阻器变阻器)in the rotor circuit, we shall obtain the short-circuit conditions of an induction machine.•The physical phenomenon of this short circuit is similar to that of a transformer short circuit, but has some distinctions resulting from the particular design features of the induction machines.•If we desire that currents I1 and I2 in the stator and rotor winding should not exceed the rated values during a short circuit, then, as in transformers, we must reduce the voltage impressed on the stator terminals to a value Usc which amounts to about 15%～25% of UN (compared with 5%～17% in transformers).电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The currents I1 and I2 create the stator and rotor , from which, according to the assumed conditions, we shall single out the first harmonic（基波基波） F1 and F2. At n=0 the rotor current frequency is equal to the stator current frequency f1. •If p is the number of pole pairs in a machine, the F1 and F2 rotate in the same direction relative to the stationary stator and rotor and at the same speed n1=60f1/p （定子磁势和转子磁定子磁势和转子磁势以相同的速度，沿相同的方向相对于静止的定子和转子势以相同的速度，沿相同的方向相对于静止的定子和转子旋转旋转）, , they are stationary in respect to each other and form the resultant （合成合成）. Fsc which rotates with speed n1 and creates the main rotating flux linked with stator and rotor windings.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•In addition, the . F1 gives rise to the primary leakage flux linked only with the primary windings, while the . F2 produces the secondary leakage flux linked only with the secondary winding.•As in the transformer, the . F1 and F2 during a short circuit are opposed to each other. Therefore, despite the considerable value of currents I1 and I2 and F1 and F2 created by them, the resultant . Fsc during a short circuit is relatively small, owing to which fluxΦsc is also small and, consequently, the main magnetic circuit is in this case not saturated.•The primary current I1 may be represented as the sum of two components, one of which ( I m ) creates the . Fsc and the other I 2’ creates the .- F2 which compensates . F2 of the secondary current I 2’ . Thus, we have电气工程及其自动化专业教研室电气工程及其自动化专业教研室The F1 and F2 being determined from the equationConsequently,orConsequently,orHence we find the current transformation factorTherefore, the referred rotor current is电气工程及其自动化专业教研室电气工程及其自动化专业教研室•Using the transformation factors for the and currents, we can determine the referred active rotor resistance r2’ and reactance x2’.•When referring r2 to the stator, we shall proceed from the consideration that the copper losses in the rotor winding are independent of referring. Consequently,Hence•where k=keki is called the resistance- referring factor(电阻折算系数电阻折算系数）.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•When referring the leakage reactance x2 to the stator, we proceed from the fact that angle θ2 between . E2 and current I2 is also independent of referring. Consequently,The equations for the primary and secondary of the induction machine at short circuit are written in exactly the same way as for transformers, namelyHence电气工程及其自动化专业教研室电气工程及其自动化专业教研室2．．3 句子成份的翻译句子成份的翻译•1 语序变动语序变动 Current sources do not exist in nature。

实际上不存在实际上不存在电流源电流源. The branch of science，artificial intelligence，is developing rapidly 人工智能人工智能这门科学分支正在迅速发展这门科学分支正在迅速发展. The triggering circuits to be described in this chapter are particularly useful. 本章要介绍的本章要介绍的这些触发电路特别有用这些触发电路特别有用. It is the best way imaginable.这是这是能想象出来的能想象出来的最好方法最好方法. The instruments present included some digital ones un-exposed.到场的到场的仪器中还有一些仪器中还有一些末公开的末公开的数字仪器数字仪器.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•2 句子成份的转换句子成份的转换 1). Theory of wavelet transform is characterized by an extensive use of maths. 小波变换理论小波变换理论的特点是的特点是广泛地应用于数学广泛地应用于数学. 2). The new devices feature wide work temperature range，low operation voltage and high reliability。

新器件新器件的特点的特点是工作温度范围宽是工作温度范围宽,工作电压低和可靠性高工作电压低和可靠性高. 3). This 150KW generator possesses an efficiency of 92 percent at full load. 满载时满载时,这台这台150千瓦千瓦发电机的效率发电机的效率是是92%. 4). Attention is necessary to prevent the electronic instrument from damaging. 必须必须注意注意防止电子仪器损坏防止电子仪器损坏.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•3 句子成份分译句子成份分译 1). There is a limit to higher transmission voltage which can be economically employed in a particular case 更高的输电电压有一个限度更高的输电电压有一个限度,从经济上看它在具体情况下是从经济上看它在具体情况下是可采用的可采用的. 2). The operation is adaptive in the sense that the tap adjustment information is derived from the received data.抽头增抽头增益调节的信息是根据所接收的数据推导出来的益调节的信息是根据所接收的数据推导出来的. 3).Two of the advantages of the transistor are its being very small in size and being able to be put close to each other without being overheated.晶体管有两大优点晶体管有两大优点:一是体一是体积小积小,二是能密集排布而不致过热二是能密集排布而不致过热.电气工程及其自动化专业教研室电气工程及其自动化专业教研室Unit 19 Armature Reaction of Salient-Pole Synchronous Machine —Two-Reaction Theory armature reaction 电枢反应电枢反应 two-reaction theory 双反应理论双反应理论salient-pole synchronous machine 凸机同步电机凸机同步电机saturation of steel 铁磁饱和铁磁饱和 non-salient-pole machine 隐极电机隐极电机the longitudinal direct-axis component纵轴分量纵轴分量the transverse, quadrature-axis component 横轴分量横轴分量电气工程及其自动化专业教研室电气工程及其自动化专业教研室the interpolar space 极间的空间极间的空间 fringing effects 边缘效应边缘效应permeability of magnetic circuit material 磁路材料的导磁率磁路材料的导磁率permeance of space 空气的导磁率空气的导磁率 coordinate origin 坐标原点坐标原点 expansion vanish 展开式展开式 rectangular wave 矩形波矩形波 size of the gap 气隙长度气隙长度 air gap 气隙气隙the direct-axis reaction factor 纵轴电枢反应系数纵轴电枢反应系数 direct-axis armature reaction reactance 纵轴电枢反应电抗纵轴电枢反应电抗form factor of the direct-axis reaction 纵轴电枢反应波形系数纵轴电枢反应波形系数电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The air gap in a salient-pole machine, even when there are no slots on the stator, is not uniform (均匀均匀）because of the presence of a large interpolar air space. The sine-wave of fundamental harmonic of the armature reaction . when interacting with the fundamental harmonic of the field winding . creates the resultant ., the axis of which is displaced from the pole axis in the alternator opposite the direction of rotation.•Since the air gap, being symmetrical in respect to （关于）（关于）the pole axis, becomes unsymmetrical relative to the axis of the resultant . displaced from the pole axis, the resultant field wave obtained due to the resultant . will be unsymmetrical and will contain higher-order harmonics (高次谐波高次谐波）of significant magnitude. Unit 19 Armature Reaction of Salient-Pole Synchronous Machine —Two-Reaction Theory 电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The wave shape of the resultant field and the fundamental wave amplitude （基波幅值基波幅值）of the field for the same resultant . amplitude will change depending on angleΨ.•To be able to take into account the quantitative effect of the armature reaction in a salient-pole machine, the phenomenon is considered as if （好像是好像是）the field （励磁磁势励磁磁势---转子磁势转子磁势）and the reaction （电枢反应磁势电枢反应磁势-定子磁势定子磁势）. create in the machine independent fluxes （各自建立磁场各自建立磁场）which induce in the stator winding independent （各自感应电动势各自感应电动势）. This greatly facilitates the quantitative estimation.• 电气工程及其自动化专业教研室电气工程及其自动化专业教研室•In the absence of saturation of the steel（铁芯存在饱和时铁芯存在饱和时）, it does not matter whether （---或或---并不重要并不重要）we find first from the . components their resultant（首先根据磁势分量求出合成磁首先根据磁势分量求出合成磁势势）, then find the resultant flux in the machine （然后求出合成然后求出合成磁通）磁通）and from this flux determine the . （根据磁通求出电动势（根据磁通求出电动势）or we find the fluxes of the . components, and determine from them the . components, and then, by vector addition of the . components, find the resultant.•Difference might have occurred if we had introduced into the consideration the effect of magnetic circuit saturation phenomena,电气工程及其自动化专业教研室电气工程及其自动化专业教研室•but since due to relatively large air gaps the saturation effect in synchronous machines is small, and if taken into account it results in great mathematical difficulties, these phenomena are neglected when analyzing armature reaction and are allowed for （考虑考虑）only indirectly when plotting the voltage diagrams（画矢量图画矢量图）.•Using the above-mentioned assumptions, the fundamental field wave due to the field . will vary proportionally to the amplitude of the fundamental . wave. All the field wave harmonics will also vary proportionally to the amplitude of the fundamental . wave.• The fundamental wave amplitude of the reaction field, however, will depend not only on the fundamental wave of the reaction . but also on angle Ψ . 电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The harmonics in the reaction field curve due to air-gap asymmetry will also depend on angle Ψ . •If we would desire, as in the case of the non-salient-pole machine, to find for the entire armature reaction field the factor ka which allows us to express the armature reaction . in terms of the field . then obviously the value of the factor would depend on angle Ψ , and would complicate the analysis.•The two-reaction theory introduced by Blondel used for analyzing this problem consists in the following.•After separating the fundamental wave from the armature reaction . by the method previously described, we resolve it into tow components along the main axis of the machine magnetic system; the longitudinal direct-axis(直轴直轴） component, 电气工程及其自动化专业教研室电气工程及其自动化专业教研室•the maximum of which coincides with the centre of the magnetic pole （与磁极中性线重合与磁极中性线重合） ，the transverse，quadrature-axis component， the maximum of which coincides with the centre of the interpolar space （与几何中与几何中性线重合性线重合）. •The amplitude of the armature reaction fundamental wave direct-axis component （直轴分量）（直轴分量） will be equal: Fad=Fasin Ψ And the amplitude of the quadrature-axis component（交轴分量）（交轴分量） is Faq=Facos Ψ 电气工程及其自动化专业教研室电气工程及其自动化专业教研室•Since each of these components does not change its position relative to the pole axis, it is possible to find for each of them an appropriate factor, viz. kad for the direct-axis and kaq for the quadrature-axis component. •These factors permit to express each of these components of the armature reaction . in terms of the field . in a manner similar to that used in finding the factor ka for the non-salient-pole machine which does not vary with （随随---变化变化）angle Ψ.•The only difference here is that in the stator winding of a non-salient-pole machine we consider one common fundamental wave . Ea due to the armature reaction, whereas in the salient-pole电气工程及其自动化专业教研室电气工程及其自动化专业教研室•machine two are considered: Ead and Eaq due to the direct-axis and quadrature-axis armature reactions, and shifted in phase by 90°(位移位移90度度）. •As the field wave shapes produced by the same fundamental wave of the armature reaction when Ψ =0 and Ψ =±π/2 will be different, it is obvious that the armature reaction factors kad and kaq for the direct and quadrature axis also obtain unequal values. •Let us analysis the armature reaction along the direct axis.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The position of the armature-reaction fundamental wave curve Fad cosα=Fa sinΨcosα is shown relative to the pole system when Ψ =±π/2. •The relation between the pole-shoe width and the pole pitch —the pole are factor —is designated by α . •The shaded areas correspond to the flux density curve, which is produced by the direct-axis sine-wave armature reaction on the assumption that （假定假定）the air gap is uniform over the pole shoe arc （极弧）（极弧）, but very small (δ≈0), this allowing for （考考虑到虑到）neglecting the fringing effects（边缘效应边缘效应）, and considering the permeability of the magnetic circuit material as infinitely great .电气工程及其自动化专业教研室电气工程及其自动化专业教研室•In this case, when neglecting the reluctance of the steel of the magnetic circuit and also the permeance of the space between the poles and the shoes (this being true for relatively small gaps), we may assume that the flux density curve in the air gap over the pole shoe has the same shape as the . curve. •Since the field loses its sinusoidal form it will induce in the stator winding , not only of the fundamental, but also of the higher-order harmonics. Let us find the factor ka that determines the decrease in amplitude of the field fundamental wave in comparison with uniform air gap, finding for this purpose the fundamental field harmonic expressed by the shaded area.•If we place the coordinate origin （坐标原点坐标原点）under the pole centre, then all the sine terms in the expansion vanish（消失消失）, and only the cosine terms remain. 电气工程及其自动化专业教研室电气工程及其自动化专业教研室•Since in the given case flux density B differs from zero only within the region -2απ/2≤α≤ απ/2, where it is equal to B=Badcosα•Bad being the maximum value of the direct-axis reaction flux density, i.e. the value of B is under the pole-shoe centre.•By integration （积分积分）we obtainThe factor kd=Bad1/Bad• The amplitude of the fundamental field harmonic Bad1 in this case will be电气工程及其自动化专业教研室电气工程及其自动化专业教研室According to the equation above withδ＝const≈0 which （系数系数）determine the degree of decrease in amplitude of the fundamental harmonic of the direct-axis armature reaction due to the air-gap non-uniformity （气隙不均匀）（气隙不均匀）and to （由于由于）the presence of the air space between the poles and pole shoes and is called the form factor （波形系数波形系数）of the direct-axis reaction. 电气工程及其自动化专业教研室电气工程及其自动化专业教研室The maximum flux density of the armature reaction direct-axis field in the general case, with stator toothing taken into account, is equal to Bad=μFad/δkδwhereδ is the size of the gap under the pole-shoe centre.Let us now find the fundamental harmonic of the field created by the pole if the gap under the pole shoe is uniform and very small, the excitation field has the shape of a rectangular wave. This curve contains a fundamental harmonic equal toIn the general case Be represents the maximum value of the excitation field flux density under the pole-shoe centre and is equal to电气工程及其自动化专业教研室电气工程及其自动化专业教研室 The field winding （find 的宾语的宾语）Fed equivalent to the armature reaction direct-axis . Fad we shall find from the condition of equality （根据等效的条件根据等效的条件）of the fundamental harmonic of the magnetic field created by these The ratio of the fundamental-wave flux density amplitude of the excitation field Be1 to the maximum flux density of this field kf =Be1/Be is called the form factor of the excitation field.With a very small and uniform gap under the pole shoe this factor is equal to电气工程及其自动化专业教研室电气工程及其自动化专业教研室is called reduction ratio of direct-axis armature . to field winding . or, in short, the direct-axis reaction factor. Whenδ＝const≈0, the factor is equal to kad=(απ+sin απ )/(4sin απ /2)Practical data pertaining to the factors （关于这个系数关于这个系数）introduced are given below.For a known value of kad the equivalent field . Fed is determined from the relationshipThe factor kad=kd/kfwhere电气工程及其自动化专业教研室电气工程及其自动化专业教研室The . Ead induced in the stator winding by the direct-axis reaction . Fad is the self-inductance . of the stator phase winding due to this field, the mutual inductance of other stator phases taken into account （考虑了其它相的互感考虑了其它相的互感）. By substituting Fad=ωeiedAn excitation current ied may also be found which is equivalent to the direct-axis component of the stator current Id=Isinφ. By the method indicated we obtain电气工程及其自动化专业教研室电气工程及其自动化专业教研室Forμ=const, the . Ead is proportional to Fad and, consequently, to the direct-axis current Id Ead=xadIdThe proportionality factor xad is the direct-axis armature reaction reactance.As a result of air-gap non-uniformity in the salient-pole machine due to pole-shoe configuration, the fundamental harmonic of the armature reaction direct-axis field decreases proportionally to kd, and the value of xad will be found by multiplying xa by kdThis relationship distinctly reveals the dependence of xad on the constructional feature of the machine.电气工程及其自动化专业教研室电气工程及其自动化专业教研室4 否定形式的转换否定形式的转换 一般否定一般否定:对谓语部分的否定；对谓语部分的否定； 特殊否定特殊否定:除谓语以外的其他成份的否定。

除谓语以外的其他成份的否定•[1]　　否定成份的转移否定成份的转移 Hydroelectric power generation uses no fuel. 水力发电水力发电不用不用燃料燃料. We don’t consider that the phase shift is proportional to frequency.我们认为相位移我们认为相位移不会不会与频率成正比与频率成正比. This version is not placed first because it is simple. 该方案该方案不是因为不是因为简单而放在首位简单而放在首位.•[2] 否定句转移为肯定句否定句转移为肯定句. We can not be too careful in doing experiment. 做实验做实验越仔细越好越仔细越好.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•[3]肯定句转移为否定句肯定句转移为否定句. It seldom makes much difference to users which winding or windings are tapped. 哪个绕组或哪些绕组上有分接头哪个绕组或哪些绕组上有分接头,对使用者来说这没有多对使用者来说这没有多大区别大区别. Fuzzy control is all Greek to me. 对模糊理论我可一窍不通对模糊理论我可一窍不通.•[4] 部分否定部分否定 有些否定句是由有些否定句是由all、、every 、、many、、both、、always和和often等含有全体意义的词和否定词等含有全体意义的词和否定词not构成的，表达的却是构成的，表达的却是部分否定的意义。

部分否定的意义Not有时与谓语动词放在一起，也构成部有时与谓语动词放在一起，也构成部分否定电气工程及其自动化专业教研室电气工程及其自动化专业教研室Not all metal conductors are used as wires considering their cost.考虑到价格考虑到价格,并非并非所有的金属导体都能用作导线所有的金属导体都能用作导线. Each transistor in the box is not out of order. 盒子里的晶体管盒子里的晶体管并非并非每一个都是坏的每一个都是坏的.•[5] 全部否定全部否定 全部否定句可由全部否定句可由none、neither、no、nor、not 、never、nothing、nobody、nowhere和和neither---nor等否定词构成等否定词构成. None of these substances are good conductors of electricity. 这些物质这些物质都不是都不是电的良导体电的良导体电气工程及其自动化专业教研室电气工程及其自动化专业教研室•[6] 双重否定双重否定 英语中的双重否定通常照译为双重否定句，但有时也可译英语中的双重否定通常照译为双重否定句，但有时也可译成肯定句。

成肯定句 There is nothing unexpected in the simulation investigation. 仿真研究时一切都在预料之中仿真研究时一切都在预料之中 There is no modern communication means that has not disadvantages. 现代通信手段都有缺点现代通信手段都有缺点.•[7] 内容否定内容否定 有些句子形式上肯定有些句子形式上肯定,内容上否定的句子内容上否定的句子. You must do anything but taking away this voltmeter. 你不能拿走这个电压表你不能拿走这个电压表电气工程及其自动化专业教研室电气工程及其自动化专业教研室Part 3 Electrical Engineering Unit 21 Technology Trends in Microcomputer Control of Electrical MachinesUnit 22 Power System Control in Next Century电气工程及其自动化专业教研室电气工程及其自动化专业教研室intelligent motion control system 智能运动控制系统智能运动控制系统electronic motion control technology 电子运动控制技术电子运动控制技术power semiconductor device 功率半导体器件功率半导体器件power integrated circuits 电力电子电力电子(无功率无功率)集成电路集成电路computer-aided design (CAD) 计算机辅助设计计算机辅助设计computer-aided manufacturing (CAM) 计算机辅助制造计算机辅助制造dedicated hardware 配置硬件配置硬件 hydraulic 液压液压electric machine drives technology 电机驱动技术电机驱动技术driven actuation system 驱动系统驱动系统 pneumatic 气动气动signal electronics 信号电子学信号电子学 Unit 21 Technology Trends in Microcomputer Control of Electrical Machines电气工程及其自动化专业教研室电气工程及其自动化专业教研室solid-state electronics 固态电子学固态电子学integrated signal electronics 集成信号电子学集成信号电子学 vacuum tube electronics 真空管电子学真空管电子学 control theory 控制理论控制理论 robot 机器人机器人saturable reactor magnetics 饱和电抗器电磁学饱和电抗器电磁学numerically controlled machine tools 数控机床数控机床general-purpose industrial drives 工业通用动力设备工业通用动力设备instrument type drives 仪表打印驱动装置仪表打印驱动装置 direct numerical control (DNC) unit 直接数字控制单元直接数字控制单元industrial automation 工业自动化工业自动化workhorse 执行机构执行机构 steam engine 蒸汽机蒸汽机microcomputer 微机微机 power electronic circuits 电力电子电路电力电子电路VLSI ---very large scale integrated circuit 大规模集成电路大规模集成电路电气工程及其自动化专业教研室电气工程及其自动化专业教研室converter circuit 换流器换流器电路电路 diagnostic capability 诊断能力诊断能力gas tube electronics 气体管电子学气体管电子学computer peripherals 计算机计算机外设外设master control 主控制主控制 disk (tape) drives 硬盘（磁带）硬盘（磁带）electronic printers 电子打印机电子打印机 nuclear power generation 核核电站电站non-manufacturing fields 非制造非制造(加工加工)业领域业领域computer-integrated manufacturing (CIM)计算机集成制造计算机集成制造 computerized numerical control (DNC) unit 计算机数字控制单元计算机数字控制单元integrated power-and-signal wiring system 电源与信号的集成电源与信号的集成接线系统接线系统automation of factories, homes, and offices 工业、家庭及办公自动化工业、家庭及办公自动化电气工程及其自动化专业教研室电气工程及其自动化专业教研室Unit 21 Technology Trends in Microcomputer Control of Electrical Machines •Computer automation of factories, homes, and offices is ushering a new era (引领新时代引领新时代） of industrial revolution. Our automated factories, homes, and offices of the future will significantly advance our industrial civilization and profoundly influence the quality of human life on this planet. Microcomputer-based intelligent motion control systems（智能运动控制系统）智能运动控制系统）which constitute the workhorses in the automated environment will play a significant role in the forthcoming（即将到来的即将到来的） era.•Electronic motion control technology has moved a long way since the introduction of power semiconductor devices（功率半导体器件）功率半导体器件）in the mid-1950’s.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•In course of its dynamic evolution during the last three decades, the area of motion control has grown as diverse interdisciplinary （多多学科交叉学科交叉）technology. The frontier（边境边境） of this technology has taken a new dimension（这个技术涉及的范围很广这个技术涉及的范围很广） with the advent of （随着（随着---出现）出现） today’s powerful microcomputers, VLSI circuits, power integrated circuits and computer-aided design (CAD) techniques.•The paper gives a comprehensive review （综述综述）of state of the motion control technology in which the salient technical features of electrical machines, power electronic circuits, microcomputer control, VLSI circuits, machine controls and computer-aided design techniques have been discussed, and wherever possible, appropriate trends of the technology have been indicated.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•Microcomputer-based intelligent motion control systems are playing a vital role in today’s industrial automation. In an automated industrial environment, a hierarchical （级联的级联的）computer system makes decisions （做出决策做出决策）about actions based on a preset strategy（预定程序预定程序）, and a motion control system, as a workhorse, translates these decisions into mechanical action.•Today‘s motion control is an area of technology （技术领域技术领域）that embraces （包括包括）many diverse disciplines, such as electrical machines, power semiconductor devices, converter circuits, dedicated hardware, signal electronics, control theory and microcomputers. More recently, the advent of VLSI/ULSI circuit and sophisticated computer-aided design techniques has added new dimensions to the technology.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•Each of the component disciplines （分支学科分支学科）is underlining（突显突显出出） an evolutionary process（进化过程进化过程）, and is contributing to（对对---作出贡献作出贡献） the total advancement （进步进步）of motion control technology. The motion control engineer today is indeed facing a challenge to keep abreast with （与与---并列，跟上并列，跟上） this complex and ever-growing multidisciplinary technology（不断发展的多学科技术不断发展的多学科技术）.•Motion control is a new term defined by the present generation of engineers（当代工程师当代工程师）. It is an offspring （分支分支）of electrical machine drives technology, which has grown at a rapid pace over the last two decades. The era of electronic motion control essentially started with the advent of power semiconductor devices in the late 1950’s, though hydraulic, pneumatic and other mechanically driven actuation systems were known for a long time（而此前很长一段时间而此前很长一段时间内，人们所熟知的是液压、气动和其它机械形式的驱动系统内，人们所熟知的是液压、气动和其它机械形式的驱动系统）. 电气工程及其自动化专业教研室电气工程及其自动化专业教研室•Gradually, the use of integrated signal electronics simplified the electronic control hardware. The introduction of microcomputers in the early 1970’s profoundly influenced motion control systems, not only by simplifying the control hardware, but by adding intelligence （智能智能）as well as diagnostic capability to the system. •We have seen an explosive growth （迅速推广迅速推广）in the application of motion control systems during recent years. Mechanical motion control systems found widespread acceptance（得到了广泛的应用得到了广泛的应用） in industry since the invention of the steam engine started the first industrial revolution in the eighteenth century, when（当时当时） mass industrial manufacturing （大型工业生产大型工业生产）replaced manual labor（手工劳动手工劳动）. 电气工程及其自动化专业教研室电气工程及其自动化专业教研室•Since then, the evolution of motion control engineering has been influenced by the development of electrical machines, vacuum tube electronics, gas tube electronics, saturable reactor magnetics, solid-state electronics and control theory. •The advent of computer technology and microelectronics during recent years has brought us to the doorstep （门坎门坎）of a second industrial revolution. Today, a tremendous momentum （巨大的冲巨大的冲力力）has developed for computer automation of our factories, homes, and offices. The principal motivation for this automation is improvement of productivity （提高了生产力提高了生产力）and quality and minimization of less predictable human elements; and these motives are being inspired by international competition. Computer-aided design (CAD) and computer-aided manufacturing (CAM) are playing increasingly important roles in factory automation. 电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The concept of computer-integrated manufacturing (CIM), in which business decisions are translated to designs, which are then translated to manufacturing through a hierarchy of computers and motion control systems, will become a reality in the near future（计算机集成制造的概念计算机集成制造的概念在不久的将来在不久的将来就会成为现实，所谓计就会成为现实，所谓计算集成制造是根据商业决策制定生产计划，然后通过计算机及算集成制造是根据商业决策制定生产计划，然后通过计算机及运动控制系统完成生产过程）运动控制系统完成生产过程）.•A motion control system, as mentioned before, is the workhorse through which higher level computer decisions are translated into mechanical actions. Motion control applications in industry include robots, numerically controlled machine tools, general-purpose industrial drives, computer peripherals and instrument type drives（仪表打印驱动装置仪表打印驱动装置）, in the home, applications include home appliance drives for washers, dryers（烘干机烘干机）, air-conditioner, blenders, mixers（搅拌机搅拌机） etc. 电气工程及其自动化专业教研室电气工程及其自动化专业教研室•In a typical computer-controlled manufacturing system on a factory floor, there are three layers of control. The master control (usually a minicomputer）operates the entire network. It includes parts transportation on and material handling （运送材料运送材料）on machine tools by robots. •The direct numerical control (DNC) unit, usually a second minicomputer（微微电脑电脑）, collects programs for the microcomputers which directly control the machine tools. •The computerized numerical control (CNC) units, in addition, contain diagnostic programs that can detect mechanical and electronic malfunctions （故障故障）in a machine tool and report them to central controllers. The data entry units （数据输入单元数据输入单元）allow communication between the operator and the DNC computer.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•In motion control systems, the application of robots is of significant interest （相当重要的相当重要的）today. The modern industrial robot was introduced by Japan in 1980, and since then, it has evolved（逐步发逐步发展展）, from performing simple tasks such as handling and transferring to performing sophisticated work, including welding，painting, assembling, inspection and adjustment. •In Japan, the world leader in factory automation, almost two-hundred-thousand robots are in operation today. This is about 60 percent of all industrial robots in the world. One noticeable trend is the growth of robot use in non-manufacturing fields, for example, nuclear power generation，medical service and welfare, agriculture, construction, transport and warehousing（仓库仓库）, underwater work and space exploration. More intelligent robots that will mimic （模仿模仿）the brain and muscles of human beings will be put to work in the future, for factory, home, or office automation.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The application of motion control has grown at a phenomenal rate （以惊人的速度以惊人的速度）in the computer peripheral industry. For example, in the U. S. alone, electronic printers, disk drives and tape drives used 24 million motors in 1983 and this figure is expected to rise to a staggering （令人吃惊的令人吃惊的）80 million by the year of 1988. It has been estimated that an average American home uses 50 motors in all the household appliances, and this amounts to （达达）a staggering 12.5 billion motors in all U. S. homes.• Eventually, all these motors will be controlled by microcomputer. In an automated home of the future, all the motors will have a central home computer-based control through an integrated power-and-signal wiring system. Similar integrated motion control concepts will be applied to automobiles（汽车汽车）, airplanes and so on.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•This report is intended to review （意欲回顾意欲回顾）the trends of motion control that relate to electrical machines, power semiconductor devices, converter microcomputers, VLSI circuits of machines and computer-aided control design techniques. Particular emphasis will be paid to （特别强调特别强调）intelligent motion control based on microcomputers. •Again, motion control systems that use small machines will be our main theme of discussion. The literature on motion control has grown enormously（迅猛地迅猛地）, and proliferated （扩散、传播扩散、传播）so diversely （按各种各样方式按各种各样方式）that it is impossible to deal with all the aspects of the technology. Therefore, only the salient features （突出的特点突出的特点）will be highlighted.电气工程及其自动化专业教研室电气工程及其自动化专业教研室Unit 22 Power System Control in Next Centurycable 电缆 power networks 电网number of blackout 故障次数 emergent technology 应急技术daily peak 高峰负荷 load patterns 负荷形式transmission grid 输电网 redundant equipment 冗余sufficient resilience 足够的恢复能力extra generator 冗余的发电机 shut-down 切除spinning reserve 旋转备用容量reactive power compensation 无功补偿器battery energy storage plant 电池储能电站maximize the utilization of system element增大系统中设备的利用率power system emergencies 电力系统紧急状态electric vehicles 电力机车 coordinated control 协调控制电气工程及其自动化专业教研室电气工程及其自动化专业教研室electric utility 电力企业 commissioning 投运fibre optic communication 光纤通信distribution feeder 配电馈线 voltage instability 电压不稳aggregate load 集中负荷 load shedding 甩负荷sub-transmission network 二次输电网continuous rating 连续运行的额定值daily load forecast 高负荷预测peak-up 峰值 fast response 快速响应main grid 主干网 black-start 黑（零）起动power system collapse (电力)系统崩溃maintenance and operational costs 维护和运行成本sustain heavy loading 承载重负荷dispersed energy storage 分布式储能renewable energy sources 可再生能源climax on the annual peak day 年峰值日的值电气工程及其自动化专业教研室电气工程及其自动化专业教研室Unit 22 Power System Control in Next Century---text•The underlying power system control function is to provide every single consumer with an electricity supply within tight bounds of frequency and voltage level while allowing them to switch appliances at any time. The community also expects a reliable and secure supply of electricity, even though consumers are widely scattered and linked by an extensive network of lines, cables and transformers which supplies the electricity from distant power stations. •In revering these tasks the electricity supply bodies are faced with difficult technical problems which have been complicated by financial constraints. The turning point proved to be the 1973～1974 oil crisis which, besides leading to a dramatic increase of fuel prices, set off a worldwide economic recession that severely curtailed the growth of electricity demand.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The financial repercussions have severely constrained electric utilities in their outlays on the power networks, at the very time when fuel costs radically altered generation patterns, leading to much higher loading on the interconnections within the transmission grid• Since the oil crisis, difficulties have been exacerbated as environmental considerations have delayed or arrested the commissioning of new power stations and transmission lines. •All these factors have contributed to changing modes of power system operation, where each utility had been self-sufficient, whereas utilities are now interdependent on neighbors because of the heavy power interchanges. Although there have been advances in the operational control of power systems, these have not kept pace with the growing operational complexities.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•Symptomatic of the system control difficulties have been the increasing number of blackouts throughout the world, many due to system voltage instability. This emphasizes the need for a new direction in power system control for overcoming the present technical difficulties as well as gaining economies for the power utilities. •Emergent technologies of energy storage（新兴储能技术新兴储能技术）, controlled power electronics and fibre optic（光纤光纤） communication offer an opportunity to develop a new direction for power system control. These could all be combined within a comprehensive control structure to straddle the entire power grid （横跨整个电网横跨整个电网）. However future developments, besides offering technical and cost effective solutions, must also consider the social factors.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The continually changing magnitude of the total system load creates the main control difficulties. Through the transmission grid, a large proportion of the control task is thrown onto the power stations, which are now distant from the cities and load centers. The intrinsic challenge is to meet the instant changes of the composite, load consisting of all the consumers and this has the most dramatic variations for the relatively short daily peak periods. The overall load changes regularly, being different on weekdays and weekends and altering with the changing seasons. •On any distribution feeder the variation of load is influenced by the relatively few consumers connected to it and the lead patterns are quite different from one distribution feeder to another. The aggregate load is supplied by the transmission grid, linked through the subtransmission network to the distribution feeder. 电气工程及其自动化专业教研室电气工程及其自动化专业教研室•At each level, there is a continual load variation, but the pattern of load chang is significantly different within distribution, subtransmission and transmission networks.•Electricity utilities make heavy capital commitments to satisfy the electricity demands of the community, as well as including large operating costs for staffing, fuel and equipment in running the power system. Further significant extra costs are included to ensure both reliability and security of electricity supplies, to meet the community’s increasing dependence on uninterrupted supplies. •Reliability is achieved by having redundant equipment that can effectively take over the function of any system element that is tripped （跌落跌落）or becomes unavailable. This requires that the continuous rating of any element would not be exceeded when another element is lost. 电气工程及其自动化专业教研室电气工程及其自动化专业教研室•Most of the redundant equipment is required for the peak load, when many elements are at their heaviest loading. With the financial, constraints now, being faced, this extra capital expenditure for the redundant equipment is posing a problem for electric utilities. Power system security is achieved by providing sufficient resilience so that the dynamic effects of disturbances on the power grid can be successfully withstood. It is the short time overload rating rather than the lower continuous rating of elements which provides this resilience. •Some disturbances can cause generator oscillations which may lead to instability. In planning a power system, a range of disturbances are studied to determine how the transmission grid should be reinforced, or if there is need for supplementary control or protections. Capital outlays on redundant system elements provided for reliability considerations add to a power system’s resilience thereby influencing security levels.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•A. C. electric energy cannot be stored, yet to hold frequency within tight hounds, generator outputs must continually match the ever varying system active power demand. Frequency is used as a control parameter to allow generator outputs to track the variations of the system load. Daily forecasts are prepared to ensure that sufficient numbers of generators are running to meet any prevailing load as it takes hours to start up thermal generators. Extra generators are connected prior to the peak-up, and later shut-down when load reduces (cycling operation). •To ensure a reliable supply and gain a fast response for unexpected events, generators hold “spinning reserve” by running at reduced outputs. This meets the utility’s obligations to the community but adds to running costs and raises thermal power station ,emissions.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•Generators produce both active and reactive power. Reactive power does not reach the consumers, whereas active power can negotiate the system network. The inherent problem is due to the much higher reactance than resistance of all transformers and EHV lines. As they become more heavily loaded, series reactive power losses increase so that any generator reactive power output is quickly dissipated well before it arrives at a consumer. •The permanent retirement of city power stations adds to the problem. Not only is electricity being sent longer distances from the now remote power stations, but it is becoming more and more difficult to build additional transmission lines, so increasing the loading on existing lines.•The most challenging problems are pond by disturbances on the main, grid as the greatest number of consumers would be effected.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The more severe disturbances greatly raise transmission line loading, suddenly increasing reactive power losses that sharply lower voltages. The post - disturbance control of reactive power and voltage pose difficulty problems because of the nature of reactive compensation. Generators and rotating units are useful and flexible as their reactive power outputs increase, when voltage levels reduce. •However reach of the reactive power compensation near the loads is by shunt capacitors whose outputs fall when voltage levels reduce. After a disturbance, when the transmission series reactive power losses increase markedly, all the extra generator outputs can only balance a portion of these extra losses but provide scant support to the affected load centers. In extreme situations the supply of reactive power to the loads cannot be sustained and has led to voltage instability and power system collapses.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•A new approach to power system control should aim to constrain the present capital intensive approach of developing power systems and yet be able to overcome many of the prevailing technical limitations. The core cause of control difficulties, the continual variation of consumer load is well recognized by power engineers, yet no strategy has been devised to attack the root of the problem. In the past, when city generators operated during peak periods, they were able to shield the transmission grid and the distant power stations from the main brunt of the peak load build up. •Battery energy storage plant—a combination of batteries and inverters—has the potential to replace city power station not only have a much faster response than existing generators, but can be directly associated with consumers in the distribution net-world. 电气工程及其自动化专业教研室电气工程及其自动化专业教研室•Potentially they could absorb the load variations of the individual consumers, and so alleviate the core power system control difficulty. There would therefore be many benefits by providing sufficient energy.•Storage to eliminate the top 10% of system peak. This overview of the operational problems and their relation to the financial and environmental constraints currently facing the power industry shows why there is need for a new approach to system control【5】. •From this vantage the following important objectives for a future system control have been formulated:•—Minimize additional capital outlays.•—Minimize system maintenance and operational costs.•—Simplify voltage and reactive power control.•—Maximize the utilization of existing system elements. (Sustain heavier loadings on lines and transformers.)电气工程及其自动化专业教研室电气工程及其自动化专业教研室•—Improve the control of power system emergencies. —Develop control measures to augment power system reliability and security.—Make provision for black-start capability.—Provide a clean power supply for all consumers.—Introduce new and renewable energy sources. The key to revering the proposed system control objectives would be the provision of a sufficient amount of energy storage. A large reservoir of stored energy that could interface with the power system can be foreseen with electric vehicles (EV). 电气工程及其自动化专业教研室电气工程及其自动化专业教研室They will have a significant presence in the next century for overcoming air and noise pollution in the cities and as a means of conserving the world’s diminishing oil reserves. It has been estimated that the world may have 1.5 million EV by 2001 .•To allow the evolution of a better and more effective power system control, the power industry would have an incentive（动力动力） for encouraging the introduction of EV as well as developing a policy for allowing operational access to the stored energy. 电气工程及其自动化专业教研室电气工程及其自动化专业教研室•In addition, EV’ will produce an increase of electricity sales that will help the industry’s finances. When EV’ come on the market in 1998,such an initiative would gain community and political approbation （批准，许可批准，许可）for the electric industry.•The greatest control difficulties are at the times of daily peak and come to a climax on the annual peak day. Utilities incur （遭受遭受）heavy capital and operational costs to meet the annual peak demand which may be of less than one hours duration. This heavy expenditure also ensures that the power system can successfully withstand disturbances occurring at this critical time. •Nonetheless, in spite of all these efforts and expenditures, power systems throughout the world are suffering gradually increasing numbers of major collapses（崩溃）.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•With its short duration, only 1% of the daily energy consumed is associated with the top 10% of demand, showing that energy storage offers an interesting prospect for curtailing （削减，限制削减，限制）the highest demands. If available, energy storage could be utilized at peak periods of every day, not just at the annual peak. Inverters, which provide the interface between D. C. stored energy and the A. C. network, are ideal as they can provide an instantaneous control of both active and reactive power.•Future developments for the coordinated control of dispersed energy storage, would provide an effective weapon against the very severe disturbances which presently cause power system collapse.电气工程及其自动化专业教研室电气工程及其自动化专业教研室•The most effective measure to counter （抵消（抵消）the effects of severe disturbances （严重干扰严重干扰）is timely and correctly located load shedding（甩负荷甩负荷）. Inverters（逆变器）逆变器）, associated with energy storage, can permit an instant increase of both active and reactive power（有功和无功功率有功和无功功率）. This has the same effect as load shedding, without any consumer being inconvenienced, but it allows a much faster response and can precisely adjust output change to match the prevailing circumstance. •Energy storage holds the promise（信守承诺信守承诺） of improving power system operation both for normal and emergency conditions（紧急情况紧急情况）. Such an edifice can provide the foundation （基础基础）for power system control in the next century.或。