继电保护原理与应用(第三版)3.1-3.5(20)

FIGURE 3.4 Polarity definitions for transformers: (a) Subtractive polarity. (b) Additive polarity. 图3.4变压器的极性定义：（a）相减极性。（b） 加性极性。
The two fundamental rules of transformer polarity, illustrated in Figure 3.4 appling to both varieties are the following:
1. Current flowing in at the polarity mark of one winding flows out of the polarity mark of the other winding. Both currents are substantially in-phase.
2. The voltage drop from polarity to nonpolarity across one winding is essentially in phase with the voltage drop from polarity to nonpolarity across the other winding(s).
图3.4所示适用于两种类型的变压器极性的两个基本规则如下：
1在一个绕组的极性标记处流入的电流从另一个绕组的极性标记处流出。两个电流基本上是同相的。
2一个绕组从极性到非极性的电压降基本上与另一个绕组从极性到非极性的电压降同相。
The currents through and the voltages across the transformers are substantially in-phase because the magnetizing current and the impedance drop through the transformers are very small and can be considered negligible. This is normal and practical for these definitions.