2023年全國碩士研究生考試考研英語一試題真題(含答案詳解+作文范文)_第1頁
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1、<p><b>  附錄四</b></p><p><b>  英文文獻(xiàn)及譯文</b></p><p>  Analysis of the reasons for the low power factor of the factory power supply system, and to improve power factor an

2、d to take effective idle work compensation measure is discussed. To saved the electrical energy, raised enterpriseps economic efficiency has important effect。</p><p>  Large and medium-sized enterprises PeiD

3、ianJian with responsibility for the whole enterprise management and distribution of electricity. At present, most of the enterprise management mode PeiDianJian obsolete, low automatization, difficult to adapt to the requ

4、irements of the development of enterprises. In view of this situation, we have developed PeiDianJian monitoring and management system. This system in the computer as the core, real-time monitoring of electric parameters,

5、 PeiDianJian all the </p><p>  We use the mains by huge power supply system is provided, all the network supply circuit is only for each of the power supply system, network, a tiny branches output. Metal wir

6、es connected by good conductors of power supply circuit, each of its source power substation, and then from that power to client to substation and its level in scale, thousands of kilometers and hundreds of kilometers of

7、 kilometers. Bare wire in the air in the vertical distribution of atmospheric mountain while high and lo</p><p>  Power supply system and electric defense methods of lightning</p><p>  Analysis

8、of the power supply system and electric easily be struck by lightning, can draw on electrical equipment, defense lightning damage, should be perfected in the power supply system, and avoid thunder lightning protection me

9、asures, the core problem is how to maximize effectively or truncate the high voltage and the thunder and lightning, strong flow under the frequency of more than 10 KHz seitching invasion.</p><p>  transforme

10、r segregation laws</p><p>  To effectively cut from the high voltage power and strong currents, currently use transformer isolation method. So-called isolation method, is based on transformer transformer equ

11、ation:</p><p>  EM = 4144fNBMS</p><p>  Type of EM for transformer original (vice), unit V; potential edge F for power source) frequency, unit (speed, N the original (vice) side of coil, The int

12、ensity of magnetic core materials BM, unit Wb/M2, S for the core area, unit M2.</p><p>  This equation, powerful lightning invade the transformer, due to transformer voltage electric ray than the normal supp

13、ly of high pressure many times, make incentive magnetic induction than the maximum allowed by magnetic core transformer core strength BM, thus the magnetic saturation, transformer -- electricity failure, GaoLei voltage t

14、ransform temporarily cannot transfer to the transformer, a deputy side of transformer protection lightning channel, the deputy of electrical equipment load. While</p><p>  Flow, fuses will fuse off. Stop So,

15、 always packed transformer electrical equipment configuration of transformer, than by lightning bad probability is greatly reduced.</p><p>  Why in the fall after the power supply, sluice stop there will sti

16、ll be struck by lightning disasters. This happened because lightning, invading transformer connected by vice and load of electrical equipment based on low, still can exist, these induction lightning induction lightning e

17、lectronics products will cause of lightning. This problem is often neglected, many lightning disasters, the event is not solved the problem. The successful development of lightning power, for we solve this problem.</p

18、><p>  Lightning arrester power</p><p>  For truncated or stop high-pressure seitching in metal wires to load caused by lightning, electric 1890 invented the clearance of the way after the lightnin

19、g series fuse, 1922 made us Westinghouse carbonized silicon arresters. To use the 1972 Japan dielectric properties research into fell seconds with no gaps (ZnO) service. Current power supply system is widely used in such

20、 power lightning.</p><p>  Zno arrester by zinc oxide thermistors, each thermistors according to need to have it made in certain switching voltage (psa). When in the lower voltage arresters ends switching vo

21、ltage (psa), high resistance thermistors present state, arrester doesn't work. When lightning arrester ends when, in the voltages above switching voltage (psa), thermistors, low resistance by breakdown, even close ci

22、rcuit state, in a very short time (50ns ´ s, 10-9) arrester is high, the work of a lightning through int</p><p>  FenLiuXing avoid thunder</p><p>  FenLiuXing avoid thunder, is the core of

23、wire cable in transmission series on two capacitor, input shunt capacitor in an inductance coil. So, when the capacitance and inductance coil capactance C L reasonable choice of inductance, make through two more than 10

24、frequency capacitor, much like KHz TV signal frequency speed to sign for dozens of hundreds of megabytes speed signals through the capacitance, and lightning frequency circuit reactance small majority in 100 KHz, when li

25、ghtning through the</p><p>  Production of equipment, such as mechanical processing machine, with various kinds of crane, with induction motor, etc, these large and electric power load is perceptual load, ma

26、ke the power factor of power supply system, the influence of distribution transformer lines and economic operation of power sector, reach the power factor, thus must adopt the reactive power compensation measures to impr

27、ove the power factor, and can save energy and reduce consumption.</p><p>  The power factor of system of power supply is an important technical and economic indexes, the power factor of electric equipment is

28、 reflected the active power and the ratio of power nai. Relevant procedure: high voltage power supply power plant, the maximum load of power factor may not be less than 0.9, Other factories, power factor may not be less

29、than 0.85.</p><p>  The main factors that affect the power factor</p><p>  The power factor of ac electric equipment, mainly because in its working process, in addition to generate power loss, a

30、lso produce reactive power loss. Therefore improving power factor the essence of the problem is to reduce the electric equipment of reactive power consumption. Asynchronous motor and power transformer is reactive power l

31、oss of the main equipment and power lines of reactive power loss, it is current through the lines. Circuit reactance.</p><p>  Parallel compensation in power capacitors supply system of factory installed pos

32、ition, have high concentrated compensation, low-pressure concentrated compensation and separate compensation on-spot three modes, etc.</p><p>  Theoretically speaking, the reactive power compensation is the

33、best way of reactive power, where is produced, the whole system where compensation will not reactive current flow, but in actual power supply system in this is impossible. We currently have a 10 kv power supply system, a

34、nd has three switch power transformer substation, three workshops 800kVA respectively, 560kVA capacity, 630kVA. Dynamic load hundreds of machine tools and machining, electric welding machine, etc. Combined with practi<

35、;/p><p>  分析了工廠供電系統(tǒng)功率因數(shù)偏低的原因,探討了提高功率因數(shù)的方法及采取的有效無功補(bǔ)償措施,對(duì)節(jié)約電能,提高企業(yè)的經(jīng)濟(jì)效益有重要意義。</p><p>  大、中型企業(yè)配電間擔(dān)負(fù)著整個(gè)企業(yè)的電力管理與分配任務(wù)。目前, 多數(shù)企業(yè)的配電間管理方式陳舊, 自動(dòng)化程度低, 難以適應(yīng)企業(yè)發(fā)展的要求。針對(duì)這種情況, 我們研制了配電間監(jiān)測與管理系統(tǒng)。該系統(tǒng)以計(jì)算機(jī)為核心, 實(shí)時(shí)監(jiān)測配電間的全

36、部電力參數(shù),經(jīng)數(shù)據(jù)處理后, 動(dòng)態(tài)顯示并輸出各類報(bào)表。該系統(tǒng)可用于企業(yè)配電間的技術(shù)更新和改造,對(duì)企業(yè)搞好計(jì)劃用電、節(jié)約用電、提高經(jīng)濟(jì)效益具有重要意義。</p><p>  我們使用的市電是由龐大的供電系統(tǒng)網(wǎng)絡(luò)提供的,每一路供電線路僅是供電系統(tǒng)網(wǎng)絡(luò)的一細(xì)小分枝輸出端。由良導(dǎo)體金屬輸電導(dǎo)線連接的每條供電線路, 其源頭從發(fā)電廠到變電站, 再到輸變電網(wǎng)再到用戶端, 其水平尺度都在數(shù)百公里、上千公里乃至上萬公里。裸露在空氣中

37、的導(dǎo)線在大氣中的垂直分布依山而高, 依箐而低, 從幾十米到幾百米上千米以至兩千米以上都常見。在這樣大范圍、垂直分布又廣的整個(gè)供變電網(wǎng)上, 由于天氣原因, 無論在哪里遭到直擊雷還是有云間放電、云內(nèi)放電,裸露在空氣中的的良導(dǎo)體導(dǎo)線很容易感應(yīng)或直接將雷電引入。這就是供電系統(tǒng)和用電設(shè)備易遭雷擊的外部氣象環(huán)境原因。</p><p>  供電系統(tǒng)和電器防御雷電的主要方法</p><p>  分析了供電

38、系統(tǒng)和電器易遭雷擊的原因, 可以得出,防御雷電對(duì)用電設(shè)備的危害, 應(yīng)該從完善供電系統(tǒng)的防雷避雷措施做起, 而且, 核心的問題就是如何最大限度地有效遏制或截?cái)噙^高的雷電壓和過強(qiáng)的雷電流, 阻止10 多KHz 以下頻率的雷電波侵入。</p><p><b>  變壓器隔離法</b></p><p>  為有效地切斷來自電網(wǎng)的高電壓和強(qiáng)電流, 目前普遍采用變壓器隔離法。所謂

39、變壓器隔離法, 就是根據(jù)變壓器方程:</p><p>  EM = 4144fNBMS</p><p>  式中EM 為變壓器原(副) 邊電勢, 單位V; f 為電源(信號(hào)源) 頻率, 單位Hz ; N 原(副) 邊線圈匝數(shù);BM 鐵芯材料的磁感應(yīng)強(qiáng)度, 單位Wb/M2 ; S 為鐵芯的截面積, 單位M2 。</p><p>  由此方程可知, 當(dāng)強(qiáng)大的雷電侵入到變

40、壓器時(shí), 由于雷電壓比電網(wǎng)給變壓器正常的供電壓高許多倍, 使得激勵(lì)的磁感應(yīng)強(qiáng)度遠(yuǎn)遠(yuǎn)大于鐵芯允許通過的最大磁感應(yīng)強(qiáng)度BM , 因而變壓器鐵芯飽和, 變壓器的磁———電變換暫時(shí)失效, 高雷電壓不能傳輸?shù)阶儔浩鞲边? 從而截?cái)嗔死纂娡ǖ? 保護(hù)了變壓器副邊所負(fù)載的用電設(shè)備。同時(shí)變壓器一般還安裝有閥型電源避雷器, 可有效將強(qiáng)大的雷電流安全引入大地, 在電流過大、電壓過高時(shí), 電</p><p>  流熔斷器會(huì)熔斷掉閘,

41、停止供電。所以, 凡是裝了變壓器的用電設(shè)備比未裝變壓器的, 被雷擊壞的機(jī)率就大大降低。</p><p>  為什么在掉閘停止供電后, 仍會(huì)有雷擊災(zāi)害發(fā)生。這是因?yàn)榘l(fā)生雷擊時(shí), 侵入變壓器副邊及連接所負(fù)載的用電設(shè)備的低壓輸電線上, 仍然還會(huì)存在有感應(yīng)雷電,這些感應(yīng)雷電仍會(huì)對(duì)電器電子產(chǎn)品造成雷電災(zāi)害。這個(gè)問題常被忽視, 不少雷電災(zāi)害事件, 究其根源, 就是沒有解決好這個(gè)問題。電源避雷器的研制成功, 為我們解決好這個(gè)問

42、題提供了幫助。</p><p><b>  電源避雷器防雷法</b></p><p>  為截?cái)嗷蜃柚垢邏豪纂姴ㄔ诮饘賹?dǎo)線上的傳播給負(fù)載電器造成雷電災(zāi)害, 自1890 年發(fā)明了間隙串聯(lián)熔斷方式的避雷器以后, 1922 年美國西屋公司制成了炭化硅避雷器。到了1972 年日本利用電介質(zhì)的伏秒特性研制成了配電用無間隙氧化鋅(ZnO) 避雷器。目前供電系統(tǒng)應(yīng)用較廣的就是這類電

43、源避雷器。</p><p>  氧化鋅避雷器由氧化鋅壓敏電阻構(gòu)成, 每塊壓敏電阻根據(jù)需要在制成時(shí)有它一定的開關(guān)電壓(壓敏電壓) 。當(dāng)加在避雷器兩端的電壓低于開關(guān)電壓(壓敏電壓) 時(shí),壓敏電阻呈現(xiàn)高阻值狀態(tài), 避雷器不工作。當(dāng)發(fā)生雷電時(shí), 加在避雷器兩端的雷電壓高于開關(guān)電壓(壓敏電壓) , 壓敏電阻被擊穿, 呈現(xiàn)低阻值狀態(tài), 甚至接近短路狀態(tài), 在很短時(shí)間( ´ 50ns , 即10 - 9 s) 避雷器

44、即導(dǎo)通工作, 將過高過強(qiáng)的雷電流經(jīng)接地線安全引入大地。當(dāng)雷電過后, 電壓趨穩(wěn), 避雷器兩端的電壓低于開關(guān)電壓(壓敏電壓) 時(shí), 壓敏電阻又呈現(xiàn)高阻值狀態(tài), 避雷器停止導(dǎo)通工作, 電力線恢復(fù)正常供電。</p><p><b>  分流型避雷法</b></p><p>  分流型避雷法, 就是在傳輸導(dǎo)線電纜的芯線串聯(lián)上兩個(gè)電容器, 在電容器輸入端并聯(lián)一個(gè)電感線圈。這樣,當(dāng)

45、電容的電容量C 和電感線圈的電感量L 合理選擇, 使通過兩個(gè)電容器、頻率比10 多KHz 高得多的如電視信號(hào)等頻率為幾十兆Hz 到幾百兆Hz 的電信號(hào)通過電容的電抗很小, 而雷電頻率絕大部分在100KHz 以下, 當(dāng)有雷電通過電容時(shí), 則會(huì)產(chǎn)生較大壓降。與通過電容的情況相反, 高頻電信號(hào)通過電感L 時(shí)產(chǎn)生較大壓降, 而頻率低得多的雷電則通過很低的阻抗, 大量泄放雷電, 經(jīng)接地線泄入大地。電視共用天線避雷器目前采用的就是這種傳輸線分流原理

46、和方法。</p><p>  生產(chǎn)所用的設(shè)備,如機(jī)械加工用的各類機(jī)床、天車,都帶有感應(yīng)電動(dòng)機(jī),還有電焊機(jī)等,這些大量的動(dòng)力負(fù)荷都是感性負(fù)荷,使得供電系統(tǒng)的功率因數(shù)偏低,影響了線路及配電變壓器的經(jīng)濟(jì)運(yùn)行,達(dá)不到電力部門的功率因數(shù)要求,因此必須采取無功功率補(bǔ)償?shù)拇胧﹣硖岣吖β室驍?shù),并能節(jié)約電能、降低損耗。</p><p>  功率因數(shù)是供用電系統(tǒng)的一項(xiàng)重要技術(shù)經(jīng)濟(jì)指標(biāo),功率因數(shù)反映的是用電設(shè)備

47、產(chǎn)生的有功功率與視在功率的比值。我國有關(guān)電力規(guī)程規(guī)定:高壓供電的工廠,最大負(fù)荷時(shí)的功率因數(shù)不得低于0.9;其它工廠,功率因數(shù)不得低于0.85。</p><p>  影響功率因數(shù)的主要因素</p><p>  功率因數(shù)的產(chǎn)生主要是因?yàn)榻涣饔秒娫O(shè)備在其工作過程中,除產(chǎn)生有功功率損耗外,還產(chǎn)生無功功率損耗。因此提高功率因數(shù)問題的實(shí)質(zhì)就是減少用電設(shè)備的無功功率損耗。異步電動(dòng)機(jī)和電力變壓器是產(chǎn)生無功

48、功率損耗的主要設(shè)備,還有供電線路產(chǎn)生的無功功率損耗,它是電流通過線路電抗所產(chǎn)生的。</p><p>  并聯(lián)補(bǔ)償?shù)碾娏﹄娙萜髟诠S供電系統(tǒng)中的裝設(shè)位置,有高壓集中補(bǔ)償、低壓集中補(bǔ)償和單獨(dú)就地補(bǔ)償?shù)热N方式</p><p>  理論上而言,無功補(bǔ)償最好的方式是在哪里產(chǎn)生無功,就在哪里補(bǔ)償,整個(gè)系統(tǒng)將沒有無功電流的流動(dòng),但在實(shí)際供電系統(tǒng)中這是不可能做到的。我廠目前供電系統(tǒng)有一個(gè)10千伏電力開關(guān)

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