chapter  1
55 Pages

Alternating Current

WithJoseph E. Fleckenstein

The common forms of alternating electricity are single phase and polyphase. Three-phase alternating current is essentially comprised of three single phases that are connected together but which peak at equally spaced time intervals. A trace of instantaneous voltage as obtained with an oscilloscope is of interest and educational. An oscilloscope trace provides a true visual picture of voltage and current as a function of time. In the study of AC circuits, and particularly three-phase circuits, it is a common practice to use phasor diagrams to depict the relationship between voltages and currents. According to common usage, the term "phase" as used in reference to three-phase electricity can have two different connotations that can result in some misunderstandings. By common usage, the three conductors of a three-phase circuit are commonly designated as the "phase A" conductor, the "phase B" conductor, and the "phase C" conductor.