電氣專業(yè)畢業(yè)設(shè)計外文翻譯

1、<p>　　附錄1：外文資料翻譯</p><p>　　A1.1外文資料題目</p><p>　　26.22 接地故障電路開關(guān)</p><p>　　我們目前為止報道的接地方法通常是充分的, 但更加進(jìn)一步的安全措施在某些情況下是必要的。假設(shè)例如, 有人將他的手指伸進(jìn)燈口（如Fig.26.45示）。雖然金屬封入物安全地接地, 但那人仍將受到痛苦的震動。或假設(shè)1

2、個120V的電爐掉入游泳池。發(fā)熱設(shè)備和聯(lián)絡(luò)裝置將導(dǎo)致電流流入在水池中的危害，即使電路的外殼被安全地接地，現(xiàn)在已經(jīng)發(fā)展為當(dāng)這樣的事件發(fā)生時，設(shè)備的電源將被切斷。如果接地電流超過5mA，接地開關(guān)將在5 ms內(nèi)跳掉，這些裝置怎么運(yùn)行的？</p><p>　　如Fig.26.46所示，一臺小變流器纏繞上導(dǎo)線 ，第二步是要連接到可能觸發(fā)開合120 V線的一臺敏感電子探測器。 在正常情況下流過導(dǎo)體的電流與中性點(diǎn)上的電流準(zhǔn)切的

3、相等，因此流經(jīng)核心的凈潮流()是零。 結(jié)果，在核心沒有產(chǎn)生電流，導(dǎo)致的電壓為零，并且開關(guān)CB沒有動作。</p><p>　　假設(shè)如果某人接觸了一個終端(圖Fig.26.45示)，故障電流將直接地從載電線漏到地面，這是可能發(fā)生的。如果絕緣材料在馬達(dá)和它的地面封入物之間斷開，故障電流也會被產(chǎn)生。在以下任何情況下，流經(jīng)CT的孔的凈潮流等于或，不再是零。電流被產(chǎn)生，并且產(chǎn)生了可以控制CB開關(guān)的電壓。 由于5 mA不平衡狀

4、態(tài)只必須被檢測出，變壓器的核心一定是非常有滲透性的在低通量密度。 Supermalloy是最為常用的，因為它有相對滲透性典型地70000在通量密度僅4mT。</p><p>　　26.23 是導(dǎo)體迅速發(fā)熱的因素</p><p>　　它有時發(fā)生于導(dǎo)體短期內(nèi)電流遠(yuǎn)大于正常值的情況下，損失非常大并且導(dǎo)體的溫度可以在數(shù)秒內(nèi)上升幾百度。例如，當(dāng)發(fā)生嚴(yán)重短路時，在保險絲或開關(guān)作用之前，會有很大的電流

5、流過導(dǎo)體和電纜。</p><p>　　此外，熱量沒有時間被消散到周圍，因此導(dǎo)體的溫度非常迅速地增加。 在這些情況下什么是溫度上升？</p><p>　　假設(shè)導(dǎo)體有大量m，電阻R和熱量熱容量c。 而且，假設(shè)電流是I，并且那它流動在t少于15秒期間。 在導(dǎo)體上引起的熱 </p><p>　　從Eq.3.17，在功率一定的情況下我們可以計算導(dǎo)體上升的溫度差：</p&

6、gt;<p><b>　　因此由</b></p><p><b>　　得出</b></p><p>　　因而斷定一個導(dǎo)體的溫度上升取決于因素。</p><p>　　眾所周知：高溫會破壞包裹在導(dǎo)體表面的絕緣。因此確定溫度上升因素是非常重要的，因為它在短路情況下，決定導(dǎo)體的溫度上升。例如，一個最初在溫度的No.2

7、AWG銅導(dǎo)體，如果它的溫度在短路時必須控制在，不可能承受因素超出。</p><p>　　一般來說，因素可以被用于計算知道(a)導(dǎo)體的橫斷面， (b)它的構(gòu)成(銅或鋁)和(c)它能承受的最高溫度。 銅和鋁的因素給出以下等式：</p><p><b>　　對于銅導(dǎo)體，</b></p><p><b>　　對于鋁導(dǎo)體，</b>&

8、lt;/p><p><b>　　其中： </b></p><p><b>　　I=短路電流（A）</b></p><p>　　t=短路的時間（s） </p><p>　　A =導(dǎo)體沒有計算空的空間的網(wǎng)橫斷面（mm） </p><p><b>　　導(dǎo)體的最初溫度()&l

9、t;/b></p><p><b>　　導(dǎo)體的最后溫度()</b></p><p>　　例子26-1___________________________________________</p><p>　　一條由鋁導(dǎo)體NO3.AWG制成且橫斷面為26.6mm的架空線。 在正常情況下這個導(dǎo)體可能連續(xù)運(yùn)載電流160 A。</p>

10、<p>　　a.在短路期間，計算最大可允許的因素，知道最初的溫度是，并且最大溫度不應(yīng)該超出。</p><p>　　b.在此架空線上有2000A的最大短路電流，問它在無需超出溫度極限的情況下運(yùn)行多久？</p><p><b>　　解答 </b></p><p>　　a.由Eq.26.5我們發(fā)現(xiàn) </p><p&

11、gt;<b>　　=</b></p><p><b>　　=7</b></p><p>　　b.2000A電流可運(yùn)行的時間t</p><p><b>　　=7</b></p><p><b>　　2000 =7</b></p><p&

12、gt;<b>　　t = 1.75s</b></p><p>　　例子26-2___________________________________________</p><p>　　它提議使用NO.30AWG銅絲作為一根臨時保險絲。 如果它最初的溫度是50，計算以下：</p><p>　　a.需要熔化導(dǎo)線的 (銅熔化在1083)</p

13、><p>　　b.如果短路電流是30A，需要熔化導(dǎo)線的時間</p><p><b>　　解答</b></p><p>　　a.由我們有的Eq.26.4 </p><p><b>　　=197 A</b></p><p>　　b.從電流為30A可得到</p><

14、p><b>　　=197</b></p><p><b>　　30</b></p><p><b>　　t=0.22s</b></p><p>　　因此，保險絲可能在220ms后被熔斷。</p><p>　　26.24 保險絲的角色</p><p&g

15、t;　　為了保護(hù)導(dǎo)體在短路期間免受過熱溫度的毀壞，一系列保險絲必須安置在導(dǎo)體上。 保險絲是經(jīng)過選擇的，目的是它的規(guī)定值比將保護(hù)導(dǎo)體上升的過熱溫度要少。 實(shí)際上，我們要保險絲在導(dǎo)體獲得一個危險溫度之前熔斷，通常采取是250。 實(shí)踐上，保險絲的規(guī)定值遠(yuǎn)在產(chǎn)生導(dǎo)體溫度的最大限度之下。 盡管如此，導(dǎo)體的規(guī)定值在保險絲的選擇時是一個重要的因素。</p><p>　　26.25 在建筑內(nèi)的電子設(shè)備安裝</p>

16、<p>　　電子分布式系統(tǒng)在建筑內(nèi)是消費(fèi)者和電能初始源之間最后的鏈接。 所有這一類建筑內(nèi)部的分布式系統(tǒng)，不管他們大或小，必須符合一些基本要求：</p><p><b>　　1.安全性</b></p><p><b>　　a.電擊的保護(hù) </b></p><p>　　b.對導(dǎo)體物理損傷的保護(hù) </p&

17、gt;<p><b>　　c.對超載保護(hù)</b></p><p>　　d.對惡劣環(huán)境的保護(hù) </p><p>　　2.導(dǎo)體的電壓降 </p><p>　　它不應(yīng)該超出1或2% </p><p><b>　　3.估計壽命 </b></p><p>　　分布

18、式系統(tǒng)應(yīng)該持續(xù)最小限度于50年 </p><p><b>　　4.經(jīng)濟(jì)性</b></p><p>　　電力設(shè)施的費(fèi)用應(yīng)該是在考慮到當(dāng)前一般標(biāo)準(zhǔn)的最小值。 </p><p>　　標(biāo)準(zhǔn)由全國電子代碼規(guī)定，并且電子設(shè)施在它可以被放入服務(wù)之前必須由審查員批準(zhǔn)。 </p><p>　　26.26 電力設(shè)施的主要成分 </

19、p><p>　　許多成分組成了電子設(shè)施。 結(jié)構(gòu)圖Figs.26.47和26.48，與以下定義一起，將幫助讀者了解某些更加重要的項目的意義。</p><p>　　1.服務(wù)導(dǎo)體 這些是在消費(fèi)者之前從街道主饋線延長或從變壓器對服務(wù)設(shè)備的導(dǎo)體。</p><p>　　2.服務(wù)設(shè)備 這些是必要的設(shè)備，通常包括開關(guān)或開關(guān)和保險絲以及他們的輔助部件，位于大廈或者其它結(jié)構(gòu)服務(wù)

20、導(dǎo)體的入口處，或是一個其他方面被定義的區(qū)域和意欲構(gòu)成主控制和切斷供應(yīng)的方法。</p><p>　　3.會議設(shè)備 各種各樣的記錄在這個前提下預(yù)測電能消耗。</p><p>　　4 鑲板 一個盤區(qū)或小組盤區(qū)單位為匯編設(shè)計了以一個唯一盤區(qū)的形式; 包括公共汽車，自動過載電流設(shè)備和有或沒有為光、熱或者功率電路控制的開關(guān)；</p><p>　　27.1

21、 核電的安全</p><p>　　盡管核電廠的安全與設(shè)計階段的決策.施工前的謹(jǐn)慎的研究以及施工本身有著直接關(guān)系，但只有在電廠真正進(jìn)入運(yùn)行階段，才有可能在各方面看到其核安全狀況，如：由于其設(shè)計缺陷出現(xiàn)的事故危險 質(zhì)量不佳或運(yùn)行故障。</p><p><b>　　保持安全水平</b></p><p>　　為了保持安全水平，首先必須遵守設(shè)計所規(guī)定的運(yùn)

22、行限制。這些限制在《安全分析報告》的“技術(shù)操作說明”中作了明確的陳述。</p><p>　　按照安全重要系統(tǒng)（IPS）進(jìn)行一項詳盡無疑的分析，同樣也是為了確定哪一種設(shè)備需要進(jìn)行定期的檢測，哪一項無需檢測（正常運(yùn)行就是運(yùn)行狀況良好的充分證明）。對每個系統(tǒng)和每次檢測來說，《檢測程序》文件對操作程序， 操作標(biāo)準(zhǔn)和要求檢測的周期等都作了明確的規(guī)定，這些規(guī)定成了運(yùn)行人員制定檢測計劃表的基礎(chǔ)。</p><

23、p>　　提高安全水平，操作經(jīng)驗反饋</p><p>　　由EDF采用的標(biāo)準(zhǔn)政策（EDF是一種主要PWR系統(tǒng)類型和有限的單個電廠序列數(shù)量）可保證通過特別重視預(yù)兆的分析極大的提高操作經(jīng)驗的價值。這有雙重目的：</p><p>　　1． 減少能夠引起發(fā)電設(shè)備不能用的事故發(fā)生頻率，即使這些事故可能對安全沒有直接關(guān)系；</p><p>　　2． 減少可能對安全造成后果的

24、嚴(yán)重事故的發(fā)生頻率，實(shí)際上，以“多層保護(hù)”和故障存在為基礎(chǔ)的核機(jī)組設(shè)計原理，認(rèn)為嚴(yán)重的事故只能是那些單獨(dú)事故和那些所謂不可能發(fā)生的事故同時發(fā)生的產(chǎn)物。</p><p>　　從核安全的角度考慮，操作反饋的主要目標(biāo)如下：</p><p>　　確認(rèn)可導(dǎo)致更為嚴(yán)重事故的預(yù)兆事故，以明確和貫徹在這類事故發(fā)生前所需采取的改正措施；</p><p>　　利用標(biāo)準(zhǔn)的機(jī)組（事故的一般

25、方面，從修改研究等方面獲取最大的效益）</p><p>　　如有必須修改之處，那么在將原理推廣到整個電廠序列之前，要保證不會產(chǎn)生相反的副作用；</p><p>　　要利用在機(jī)組實(shí)際運(yùn)行中所獲得的數(shù)據(jù)，以統(tǒng)一安全標(biāo)準(zhǔn)，特別是對新廠更需要如此。</p><p>　　EDF是按如下方針制定其操作經(jīng)驗反饋系統(tǒng)的：</p><p>　　系統(tǒng)地收集盡可能

26、多的數(shù)據(jù)資料，盡可能廣泛地交流收集到的數(shù)據(jù)，特別是在EDF范圍內(nèi)；</p><p>　　在數(shù)據(jù)分析過程中，要盡可能地讓設(shè)計人員，運(yùn)行人員，制造廠商和安全機(jī)構(gòu)一起參與；</p><p>　　吸取經(jīng)驗，這不僅有益于那些正在計劃和建設(shè)中的機(jī)組，而且有益于那些目前正在運(yùn)行的機(jī)組。</p><p>　　A1.2外文資料題目</p><p>　　26.2

27、2 Ground-fault circuit breaker</p><p>　　The grounding methods we have covered so far are usually adequate,but further safety measures are needed in some cases.Suppose foe example , that a person sticks his f

28、inger into a lamp socket (Fig.26.45).Although the metal enclosure is securely grounded, the person will still receive a painful shock. Or suppose a 120 V eletric toster tumbles into a swimming pool. The heating elements

29、and contacts will produce a hazardos leakage current throughout the pool ,ven if the frame of the toaster is secu</p><p>　　A small current transformer surrounds the live and neutral wires as shown in Fig.26.

30、46. The secondary is connected to a sensitive electronic detetor that can trigged a circuit breaker CB that is in series with the 120 V line. Under normal conditions the current Iin the line conductor is exactly equal to

31、 thecurrent Iin the neutral ,and so the net current (I-I) flowing through the hole in the toroidal core is zero. Consequently, no flux is produced in the core, the induced voltage E is zero, and b</p><p>　　S

32、uppose now that a fault current I leaks directly from the live wire to ground . This could happen if someone touched a live terminal (Fig.26.45). A fault current I would also be produced if the insulation broke down betw

33、een a motor and its grounded enclosure . Under any of these conditions, the net current flowing through the hole of the CT is no longer zero but equal to I or I. A flux is set up and a voltage E is induced, which trips C

34、B. Because an imbalance of only 5 mA has to be detected, th</p><p>　　26.23 rapid conductor heating: the It factor </p><p>　　It sometimes happens that a current far greater than normal flows for

35、a brief period in a conductor . The Ilosses are than very large and the temperature of the conductor can rise several hundred degrees in a fraction of a second . For example, during a severe short-circuit, intense curren

36、ts can flow in conductors and cables before the circuit is opened by the fuse or circuit breaker.</p><p>　　Furthermore, the heat does not have time to be dissipated to the surroundings and so the temperature

37、 of the conductor increases very rapidly. What is the temperature rise under these condition?</p><p>　　Suppose the conductor has a mass m, a resistance R, and a thermal heat capacity c. Moreover, suppose the

38、 current is I and that it flows for a period t that is typically less than 15 seconds. The heat generated in the conductor is given by </p><p>　　Form Eq.3.17,we can calculate the temperature rise for a given

39、 value of :</p><p><b>　　hence </b></p><p>　　from which </p><p>　　If follows that for a given conductor the temperature rise depends upon the I factor .</p><p&

40、gt;　　It is well known that high temperature damage the insulation that covers a conductor. The I factor is ,therefore ,very important because it determines the temperature rise under short-circuit conditions. For example

41、 , a No.2AWG copper conductor, initially at a temperature of 90,cannot endure an I factor in eccess of 22s if its temperature is to be limited to 250during a short-circuit.</p><p>　　In general, the I factor

42、can be calculated knowing (a) the cross section of the conductor, (b) its composition(copper or aluminum), and (c) the maximum temperature it can tolerate. The I factor for copper and aluminum conductors are given by the

43、 following equations:</p><p>　　for copper conductors,</p><p>　　for aluminum conductors,</p><p><b>　　where </b></p><p>　　I =short-circuit current</p>

44、<p>　　duration of the short-circuit</p><p>　　A = net cross-section of conductor without counting the empty spaces</p><p>　　initial temperature of conductor </p><p>　　final temp

45、erature of conductor </p><p>　　Example 26-1___________________________________________</p><p>　　An overhead line made of aluminum conductor No.3 AWG has a cross-section of 26.6mm . Under normal

46、conditions this conductor can continuously carry a current of 160 A.</p><p>　　Calculate the manximum permissible I factor during a short-circuit, knowing that the initial temperature is 80and that the manxim

47、um temperature should not exceed 250.</p><p>　　A manximum short-circuit of 2000 A is foreseen on this overhead line. For how long can it circulate without exceeding the 250 temperature limit?</p><

48、p><b>　　Solution </b></p><p>　　Using Eq.26.5 we find </p><p><b>　　=)</b></p><p><b>　　=7</b></p><p>　　The 2000 A current can flow f

49、or a time t given by </p><p><b>　　I=7</b></p><p><b>　　2000 =7</b></p><p><b>　　t = 1.75s</b></p><p>　　Example 26-1__________________

50、_________________________</p><p>　　It is proposed to use a No.30 AWG copper wire as a temporary fuse. If its initial temperature is 50, calculate the following :</p><p>　　The I needed to melt th

51、e wire ( copper melts at 1083)</p><p>　　The time needed to melt the wire if the short circuit current is 30 A</p><p><b>　　Solution</b></p><p>　　Form Eq.26.4 we have <

52、/p><p><b>　　=197 A</b></p><p>　　For a current of 30 A we obtain </p><p><b>　　I=197</b></p><p><b>　　30</b></p><p><b>

53、　　t=0.22s</b></p><p>　　Thus, the fuse will blow in approximately 220ms. </p><p>　　26.24 The role of fuses</p><p>　　In order to protect a conductor from excessive temperature d

54、uring a short-circuit, a fuse must be placed in series with the conductor. The fuse must be selected so that its I rating is less than that which will protect an excessive temperature rise of the conductor. In effect, w

55、e want the fuse to blow before the conductor attains a dangerous temperature, usually taken to be 250. In practice, the I rating of the fuse is such as to product conductor temperatures far below this maximum limit. Neve

56、</p><p>　　26.25 Electrical installation in buildings </p><p>　　The electrical distribution system in a building is the final link between the consumer and the original source of electrical energ

57、y. All such in-house distribution systems, be they large or small, must meet certain basic requirements:</p><p><b>　　Safety </b></p><p>　　Protection against electric shock </p>

58、<p>　　Protection of conductors against physical damage </p><p>　　Protection against overloads </p><p>　　Protection against hostile environments </p><p>　　Conductor voltage dr

59、op </p><p>　　It should not exceed 1 or 2 percent </p><p>　　Life expectancy </p><p>　　The distribution system should last a minimum of 50 years </p><p><b>　　Econom

60、y </b></p><p>　　The cost of the installation should be minimized while observing the pertinent standards. </p><p>　　Standards are set by the National Electrical Code and every electrical i

61、nstallation must be approved by an inspector before it can be put into service. </p><p>　　26.26 Principal components of an electrical installation </p><p>　　Many components are used in the marku

62、p of an electrical installation. The block diagrams of Figs.26.47 and 26.48, together with the following definitions, will help the reader understand the purpose of some of the more important items.</p><p>　

63、　Service Conductors. These are the conductors that extend form the street main or form a transformer to the service equipment on the consumer premises.</p><p>　　Service Equipment. The necessary equip

64、ment, usually consisting of a circuit breaker or switch and fuses, and their accessories, located near the point of entrance of service conductors to a building or other structure, or an otherwise defined area, and inten

65、ded to constitute the main control and means of cutoff of the supply.</p><p>　　Meeting Equipment. Various meters and recorders to indicate the electrical energy consumed on the premises.</p><p>

66、　　Panel Board. A single panel or group of panel units designed for assembly in the form of a single panel; including buses, automatic over current devices, and with or without switches for the control of light, heat, or

67、power circuits;</p><p><b>　　Safety </b></p><p>　　Although the safety of a nuclear power plant is directly linked to the decision taken at the design stage and to the care taken in pr

68、e-construction studies and construction itself, it is only really in operation that nuclear safety can be seen in all its various facets, i.e. the risk of accident due to weaknesses in the design, insufficient quality or

69、 operational error.</p><p>　　Maintaining the Safety level </p><p>　　In order to maintain the level of safety, it is first of all necessary to observe the operational limits of the design. These

70、limitations are set out in the “Technical Operating Specifications” volume of the Safety Analysis Report.</p><p>　　An exhaustive analysis is also carried out on systems Important For Safety (IPS) to identify

71、 which equipment is required to undergo periodic testing and to justify which items do not require testing (normal operation is sufficient proof of good working order). For each system and test the “Test Procedure” docu

72、ment specifies the operating procedure, criteria and the required testing intervals. These instructions are used by the operators as the basis for preparing “Test Schedules”.</p><p>　　27.1 Safety of Nuclear

73、electricity</p><p>　　The standardization policy adopted by EDF (one major PWR system type and a limited number of individual plant series) justifies a major commitment to maximizing the value of operational

74、experience by placing particular emphasis on the analysis of precursor incidents. This has a dual purpose:</p><p>　　To reduce the frequency of serious incidents liable to result in the generating equipment b

75、ecoming unavailable, even if these is no direct bearing on safety.</p><p>　　To reduce the frequency of incidents likely to have consequences to safety , in practice, the design principles for nuclear units b

76、ased on Defence In Depth and the presence of barriers are such that serious accidents could only result from a simultaneous combination of independent and improbable incidents.</p><p>　　In terms of nuclear s

77、afety, the principal objectives of operational feedback are as follows:</p><p>　　# to identify precursor incidents leading to more serious accidents in order to define and implement any corrective measures

78、required before any such accidents occur.</p><p>　　# to take adventage of standardized units (the generic aspects of incidents, deriving maximum benefit from modification studies, ect )</p><p>

79、　　# to ensure, in cases where modification is necessary, that these are no adverse secondary effects before principle is extended to the entire plant series.</p><p>　　# to utilize data gathered during actu

80、al operation of the installation in order to unify the level of safety, especially in the case of a new plant series.</p><p>　　The guidelines on which EDF has based its operational experience feedback system

81、 are as follows:</p><p>　　To systematically gather the maximum amount of data and circulate it as widely as possible, particularly within EDF.</p><p>　　To bring together as many as possible Desi

82、gners. Operators, Manufacturers and Safety Authorities in the data analysis process.</p><p>　　To lean from experience on order to benefit not only those units planned or under construction but also units cur