變電所畢業(yè)設(shè)計(jì)外文翻譯-其他專業(yè)-資料下載頁
2025-01-19 08:12本頁面
【導(dǎo)讀】要從遠(yuǎn)端發(fā)電廠送出電能，必須應(yīng)用高壓輸電。因?yàn)樽罱K的負(fù)荷，在一些點(diǎn)。高電壓必須降低。變壓器能使電力系統(tǒng)各個(gè)部分運(yùn)行在電壓不同的等級。們討論的原則和電力變壓器的應(yīng)用。變壓器的最簡單形式包括兩個(gè)磁通相互耦合的固定線圈?；ヱ詈?，是因?yàn)樗鼈冞B接著共同的磁通。為它沒有旋轉(zhuǎn)損失，因此在電壓等級轉(zhuǎn)換的過程中，能量損失比較少。率范圍在92到99%，上限值適用于大功率變壓器。從交流電源流入電流的一側(cè)被稱為變壓器的一次側(cè)繞組或者是原邊。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。組被稱為變壓器的二次側(cè)繞組或者是副邊。磁通是變化的；因此依據(jù)楞次定律，當(dāng)二次側(cè)電路開路是，即使原邊被施以正弦電壓Vp，也是沒有能量轉(zhuǎn)移的。這兩種相關(guān)的損耗被稱為鐵。應(yīng)電壓Es可以表示出來。后于磁通90º，因此，它于施加的電壓有180º的相位差。小，并且Vp的值近乎等于Ep?？偟膩碚f，變壓器為了保持磁通是常數(shù)，對磁通變化的響應(yīng)是瞬時(shí)的。
【正文】 n the first place. Of course, this is Lenz’s law in action. Thus the MMF represented by NsIs tends to reduce the core flux φ0. This means that the flux linking the primary winding reduces and consequently the primary induced voltage Ep, This reduction in induced voltage causes a greater difference between the impressed voltage and the counter induced EMF, thereby 9 allowing more current to flow in the primary. The fact that primary current Ip increases means that the two conditions stated earlier are fulfilled: (1) the power input increases to match the power output, and (2) the primary MMF increases to offset the tendency of the secondary MMF to reduce the flux. In general, it will be found that the transformer reacts almost instantaneously to keep the resultant core flux essentially constant. Moreover, the core flux φ0 drops very slightly between n o load and full load (about 1 to 3%), a necessary condition if Ep is to fall sufficiently to allow an increase in Ip. On the primary side, Ip’ is the current that flows in the primary to balance the demagizing effect of Is. Its MMF NpIp’ sets up a flux linking the primary only. Since the core flux φ0 remains constant. I0 must be the same current that energizes the transformer at no load. The primary current Ip is therefore the sum of the current Ip’ and I0. Because the noload current is relatively small, it is correct to assume that the primary ampereturns equal the secondary ampereturns, since it is under this condition that the core flux is essentially constant. Thus we will assume that I0 is negligible, as it is only a small ponent of the fullload current. When a current flows in the secondary winding, the resulting MMF (NsIs) creates a separate flux, apart from the flux φ0 produced by I0, which links the secondary winding only. This flux does no link with the primary winding and is therefore not a mutual flux. In addition, the load current that flows through the primary winding creates a flux that links with the primary winding only。 it is called the primary leakage flux. The secondary leakage flux gives rise to an induced voltage that is not counter balanced by an equivalent induced voltage in the primary. Similarly, the voltage induced in the primary is not counterbalanced in the secondary winding. Consequently, these two induced voltages behave like voltage drops, generally called leakage reactance voltage drops. Furthermore, each winding has some resistance, which produces a resistive voltage drop. When taken into account, these additional voltage drops would plete the equivalent circuit diagram of a practical transformer. Note that the magizing branch is shown in this circuit, which for our purposes will be disregarded. This follows our earlier assumption that the noload current is assumed negligible in our calculations. This is further justified in that it is rarely necessary to predict transformer performance to such accuracies. Since the voltage drops are all directly proportional to the load current, it means that at noload conditions there will be no voltage drops in either winding.
環(huán)評公示相關(guān)推薦
鄂ICP備17016276號-1