A term applied to groups of currents of alternating type which
constantly differ from each other by a constant proportion of periods of
alternation. They are produced on a single dynamo, the winding being so
contrived that two, three or more currents differing a constant amount
in phase are collected from corresponding contact rings. There are
virtually as many windings on the armature as there are currents to be
produced. Separate conductors for the currents must be used throughout.

Synonyms–Polyphase Currents–Rotatory Currents.