1、第十一章 AT供電系統(tǒng),Department of Electrical Engineering,自耦變壓器供電方式 (AT) Auto-transformer,日本鐵路為防止通訊干擾，在實行交流電氣化的前期，在牽引網(wǎng)中普遍應用了BT供電方式。 但當高速、大功率機車在這種電路中通過吸流變壓器分段時，在受電弓上會產(chǎn)生強烈電弧，為了克服此缺點，后來發(fā)展了一種新的牽引網(wǎng)供電方式自耦變壓器供電方式，AT間隔為10km左右。,Department of Electrical Engineering,自耦變壓器的工作原理,原邊和副邊共用一部分繞組的變壓器稱為自耦變壓器。可設想為從一臺普通雙繞組變壓器演變而

2、來。 1.電壓、電流關系 其原次邊的電壓、 電流關系與雙繞組變壓器一樣。 2.容量關系 對于雙繞組變壓器， 原繞組容量就是變壓器的輸入容量，副繞組容量就是變壓器輸出容量，都等于變壓器的容量。 對于自耦變壓器，變壓器容量與繞組容量不相等。,Auto transformer,A step-down auto-transformer: the voltage at the input is the sum of the voltages on the series winding and the common winding, while the voltage at the output is j

3、ust the voltage on the common winding.,Voltage and Current Relationship in an Autotransformer,Auto-Transformer feeding system,The Apparent Rating Advantage of AT,SIO is defined to be the input and output apparent powers of the transformer.,However, the apparent power in the transformer windings is,T

4、herefore, the ratio of the apparent power in the primary and secondary of the AT to the apparent power actually traveling through its windings is This equation describes the apparent power rating advantage of an AT over a conventional transformer.,SIO is the apparent power entering the primary and l

5、eaving the secondary of the transformer, while SW is the apparent power actually traveling through the transformers windings.,For example, a 32MVA AT connecting a 55kV system to a 27.5kV system: The turns ratio:,The AT would have windings rated at only about 16MVA, while a conventional transformer d

6、oing the same jog would need windings rated at 32MVA.,Department of Electrical Engineering,AT供電方式的特點,輸入電壓是輸出電壓的2倍，輸入電流為輸出電流的一半。 AT供電方式無需提高牽引網(wǎng)的絕緣水平即可將牽引回路的供電電壓提高一倍。可以大大增加牽引變電所的間距，一般可達100km左右，減少牽引變電所的數(shù)目。 自耦變壓器是并聯(lián)在接觸懸掛和正饋線之間的，提高了供電可靠性。,Department of Electrical Engineering,AT供電方式有效地減弱對通信線的感應影響。 大部分回流沿正饋線流回牽引變電所，減小了地中電流。同時，接觸網(wǎng)中的電流與正饋線的電流大小相同，方向相反，兩者的交變磁場可以相互抵消。因此，AT供電的防干擾性能十分理想。,Department of Electrical Engineering,11.2 單線AT網(wǎng)絡,假設： 忽略自耦變壓器漏抗，即認為ZAT=0； 假設鋼軌對地漏導為零，即不考慮短回路的地中電流； 假設接觸網(wǎng)、正饋線關于鋼軌對稱布置，而且接觸網(wǎng)、正饋線自阻抗相當，即ZC=ZF，ZCT=ZFT。,Department of