电气工程方面的英汉论文.doc

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Electric Devices and Systems
Although transformers have no moving parts , they are linkages in each coil will be. Voltages will be induced in these two coil.
On the other hand, currents flowing in the coils are related to the field intensity H. if currents flowing in the direction shown, i1 into the dotted terminal of coil 1, and i2 out of the dotted terminal of coil 2. we recognize that this is practically impossible, but so is the e*istence of an ideal transformer.
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Equations describe this ideal transformer, a two port network. The symbol of a network that is defined by these two equations is in the figure. An ideal transformer has an interesting characteristic. A two-port network that contains it and impedances can be replaced by an equivalent other, as discussed below. Consider the circuit in figure. Seen as a two port network. Generally a circuit on a side 1 can be transferred to side 2 by multiplying its ponent impedances , the voltage sources and the current sources, while keeping the topology the same. To develop the equivalent for a transformer we’ll gradually rela* the assumptions that we had first imposed. First we’ll rela* the assumption that the permeability of the iron is infinite. In that case equation does not revert to, but rather it bees where is the reluctance of the path around the core of the transformer and the flu* on this path. To preserve the ideal transformer equations as part of our new transformer, we can split i1 to two ponents: one i1, will satisfy the ideal transformer equation, and the other, i1 will just balance the right hand side. The figure shows this. We can replace the current source, i1 , with something simpler if we remember that the rate of change of flu* is related to the induced voltage.
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Since the current i1 flows through something , where the voltage across it Is proportional to its derivative, we can consider tha