电气毕业设计用外文翻译(中英文对照)--负载运行的变压器及直流电机导论
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1、中文 5580 字,3500英文单词,17500英文字符 The Transformer on load Introduction to DC Machines The Transformer on load It has been shown that a primary input voltage 1V can be transformed to any desired open-circuit secondary voltage 2E by a suitable choice of turns ratio. 2E is available for c
2、irculating a load current impedance. For the moment, a lagging power factor will be considered. The secondary current and the resulting ampere-turns 22NI will change the flux, tending to demagnetize the core, reduce m and with it 1E . Because the primary leakage impedance drop is so low,
3、 a small alteration to 1E will cause an appreciable increase of primary current from 0I to a new value of 1I equal to ijXREV 111 / . The extra primary current and ampere-turns nearly cancel the whole of the secondary ampere-turns. This being so , the mutual flux suffers only a slig
4、ht modification and requires practically the same net ampere-turns 10NI as on no load. The total primary ampere-turns are increased by an amount 22NI necessary to neutralize the same amount of secondary ampere-turns. In the vector equation , 102211 NININI ; alternatively, 221011 NININI .
5、 At full load, the current 0I is only about 5% of the full-load current and so 1I is nearly equal to 122 / NNI . Because in mind that 2121 / NNEE , the input kVA which is approximately 11IE is also approximately equal to the output kVA, 22IE . The physical current has increased, an
6、d with in the primary leakage flux to which it is proportional. The total flux linking the primary ,111 mp, is shown unchanged because the total back e.m.f.,( dtdNE /111 ) is still equal and opposite to 1V . However, there has been a redistribution of flux and the mutual component has fallen due to
7、the increase of 1 with 1I . Although the change is small, the secondary demand could not be met without a mutual flux and e.m.f. alteration to permit primary current to change. The net flux s linking the secondary winding has been further reduced by the establishment of secondary leakage flux
8、due to 2I , and this opposes m . Although m and 2 are indicated separately , they combine to one resultant in the core which will be downwards at the instant shown. Thus the secondary terminal voltage is reduced to dtdNV S /22 which can be considered in two components, i.e. dtdNdtd
9、NV m / 2222 or vectorially 2222 IjXEV . As for the primary, 2 is responsible for a substantially constant secondary leakage inductance 222222 / NiN . It will be noticed that the primary leakage flux is responsible for part of the change in the secondary terminal voltage due to its effects on t
10、he mutual flux. The two leakage fluxes are closely related; 2 , for example, by its demagnetizing action on m has caused the changes on the primary side which led to the establishment of primary leakage flux. If a low enough leading power factor is considered, the total secondary flux and the
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