Fig. 1,394.—Diagram showing essential parts of a revolving field alternator and method of joining the parts in assembling.
3. Only two collector rings are required.
4. The armature terminals, being stationary, may be enclosed permanently so that no one can come in contact with them.
Ques. What names are usually applied to the armature and field magnets with respect to which moves?
Ans. The "stator" and the "rotor."
The terms armature and field magnets are to be preferred to such expressions. An armature is an armature, no matter whether it move or be fixed, and the same applies to the field magnets. There is no good reason to apply other terms which do not define the parts.
Ques. Explain the essential features of a revolving field alternator.
Ans. The construction of such alternators is indicated in the diagram, fig. 1,394. Attached to the shaft is a field core, which carries the latter, consisting of field coils fitted on pole pieces which are dovetailed to the field core. The armature is built into the frame and surrounds the magnets as shown. The field current, which is transmitted to the magnets by slip rings and brushes, consists of direct current of comparatively low pressure, obtained from some external source.
