求电专业英语翻译￥￥

求电专业英语翻译￥￥
A three-phase electric circuit is energized by three alternating emfs of the same frequency and differing in time phase by 120 electrical degrees. Three such sine-wave emfs are shown in Fig. 1-1B-1. These emfs are generated in three sets of coils are mounted 120 electrical degrees apart on the generator armature. The coil ends may all be brought out of the generator to form three separate single-phase circuits. However, The coils are ordinarily interconnected either internally or externally to form a three wire or four-wire three-phase system.
Active electrical elements occur in two basic forms: Voltage sources and current sources. In their ideal form, voltage sources generate a constant voltage independent of the current drawn form the source. The aforementioned battery and generator are regarded as voltage sources since their voltage is essentially constant with load, On the other hand, current sources produce a current whose magnitude is independent of the load connected to the source. Although current sources are not as familiar in practice, the concept does find wide use in representing an amplifying device, such as the transistor, by means of an equivalent electrical circuit. Symbolic representations of voltage and current sources are shown in Fig. 1-1A-2.