畢業(yè)設(shè)計-建筑電氣專業(yè)畢業(yè)設(shè)計英文翻譯(存儲版)
【正文】 p and Es vary as a sine function. The average value of the induced voltage given by Eavg = turns c h a n g e in flu x in a g iv e n tim eg iv e n tim e which is Faraday’s law applied to a finite time interval. It follows that Eavg = N21/(2 )mf? = 4fNφm which N is the number of turns on the winding. Form ac circuit theory, the effective or rootmeansquare (rms) voltage for a sine wave is times the average voltage。s key position, the electric power supply directs the transformer substation from the electrical work, pletes the voltage dropping in the transformer substation, functions and so on electrical energy assignment. Keywords: substation； transformer； Relay protection； 1. INTRODUCTION The highvoltage transmission was need for the case electrical power is to be provided at considerable distance from a generating station. At some point this high voltage must be reduced, because ultimately is must supply a load. The transformer makes it possible for various parts of a power system to operate at different voltage levels. In this paper we discuss power transformer principles and applications. 2. TOWWINDING TRANSFORMERS A transformer in its simplest form consists of two stationary coils coupled by a mutual magic flux. The coils are said to be mutually coupled because they link a mon flux. In power applications, laminated steel core transformers (to which this paper is restricted) are used. Transformers are efficient because the rotational losses normally associated with rotating machine are absent, so relatively little power is lost when transforming power from one voltage level to another. Typical efficiencies are in the range 92 to 99%, the higher values applying to the larger power transformers. The current flowing in the coil connected to the ac source is called the primary winding or simply the primary. It sets up the flux φ in the core, which varies periodically both in magnitude and direction. The flux links the second coil, called the secondary winding or simply secondary. The flux is changing。因此，這兩個增大的電壓具有電壓 降的性質(zhì)，總稱為漏電抗電壓降。 因為空載電流相 對較小，那么一次側(cè)的安匝數(shù)與二次側(cè)的安匝數(shù)相等的假設(shè)是成立的。換句話說，極性的標(biāo)注可以表明當(dāng)電流流過兩側(cè)的線圈時，線圈中的磁動勢會增加。 從電源側(cè)來看變壓器，其阻抗可認(rèn)為等于 Vp / Ip。 當(dāng)副邊電壓 Vs 相對于原邊電壓減小時，這個變壓器就叫做降壓變壓器。用字母 a 來表示這個比率，如下式 a = psEE = psNN 假設(shè)變壓器輸出電能等于其輸入電能 —— 這個假設(shè)適用于高效率的變壓器。一次側(cè)空載電流很小，僅為滿載電流的百分之幾。這種情況是非線性鐵芯材料造成的。這兩種相關(guān)的損耗被稱為鐵芯損耗。它在鐵圈中建立了磁通 φ，它的幅值和方向都會發(fā)生周期性的變化。變壓器能使電力系統(tǒng)各個部分運行在電壓不同的等級。 變配電所是實現(xiàn)電壓等級變換和電能分配的場所。兩個線圈之所以相互耦合，是因為它們連接著共同的磁通。變壓器在原邊接收電能的同時也在向副邊所帶的負(fù)荷輸送電能。顯然可見電流分量 Im= I0sinθ0，被稱做勵磁電流，它在相位上滯后于原邊電壓 VP 90186。相同的磁通會通過原邊自身，產(chǎn)生一個電動勢 Ep。產(chǎn)生電壓的平均值如下 Eavg = turns給 定 時 間 內(nèi) 磁 通 變 化 量給 定 時 間 即是法拉第定律在瞬時時間里的應(yīng)用。在上面公式中一次側(cè)和二次側(cè)的功率因素是相等的；因此 VpIp = VsIs 從上式我們可以得知 psVV = psII ≌ psEE ≌ a 它表明端電壓比等于匝數(shù)比，換句話說，一次側(cè)和二次側(cè)電流比與匝數(shù)比成反比。當(dāng) a=1 時，變壓器的二次側(cè)電壓就等于起一次側(cè)電壓。我們把這種折算方式稱為負(fù)載阻抗向一次側(cè)的折算。其需要的條件是 E 降落很多來使電流 Ip 增加。 當(dāng)一個電流流過二次側(cè)繞組，它的磁動勢（ NsIs）將產(chǎn)生一個磁通，于空載電流I0 產(chǎn)生的磁通 φ0 不同，它只停留在二次側(cè)繞組中。由于分支勵磁體現(xiàn)在電流里，為了分析我們可以將它忽略。. It is readily seen that the c
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