外文翻譯---負載運行的變壓器-其他專業(yè)(文件)
【正文】 ting resistance, it still has to provide a total back . equal to 1V . It is virtually the same as 11? , though now produced by the bined effect of primary and secondary ampereturns. The mutual flux must still change with load to give a change of 1E and permit more primary current to flow. 1E has increased this time but due to the vector bination with 1V there is still an increase of primary current. Two more points should be made about the figures. Firstly, a unity turns ratio has been assumed for convenience so that 39。39。 RNNR ? and 22212 )/(39。XI will be found to check as 39。 IENNINNEIEk V A ???? . The argument is sound, though at first it may have seemed suspect. In fact, if the actual secondary 7 winding was removed physically from the core and replaced by the equivalent winding and load circuit designed to give the parameters 1N , 39。 . 239。2 RR ? and 1239。2V ,or (b) viewed from the secondary as a source of constant voltage 1V with internal drops due to 1Re and 1Xe . The magizing branch is sometimes omitted in this representation and so the circuit reduces to a generator producing a constant voltage 1E (actually equal to 1V ) and having an internal impedance jXR? (actually equal to 11Re jXe? ). In either case, the parameters could be referred to the secondary winding and this may save calculation time . The resistances and reactances can be obtained from two simple light load tests. 。2V to 2V .All calculations of internal voltage and power losses are made before this ideal transformation is applied. The behaviour of a transformer as detected at both sets of terminals is the same as the behaviour detected at the corresponding terminals of this circuit when the appropriate parameters are inserted. The slightly different representation showing the coils 1N and 2N side by side with a core in between is only used for convenience. On the transformer itself, the coils are , of course , wound round the same core. Very little error is introduced if the magising branch is transferred to the primary terminals, but a few anomalies will arise. For example ,the current shown flowing through the primary impedance is no longer the whole of the primary current. The error is quite small since 0I is usually such a small fraction of 1I . Slightly different answers may be obtained to a particular problem depending on whether or not allowance is made for this error. With this simplified circuit, the primary and referred secondary impedances can be added to give: 221211 )/(Re NNRR ?? and 221211 )/( NNXXXe ?? It should be pointed out that the equivalent circuit as derived here is only valid for normal operation at power frequencies。 XX ? 。2X and 39。 22 XI . The referred secondary 2212221222 )/()/(39。39。/39。 ENNE ? which is
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