INDUCTOR MACHINES

283

phase field, as in Fig. 139, we use a polyphase exciting field. This
is shown, with three exciting coils or poles energized by three-
phase currents, in Fig. 141. The high-frequency voltages of
pulsating amplitude, induced by the three phases, then super-
pose a high-frequency wave of constant amplitude, and we get,
in Fig. 141, a high-frequency alternator with polyphase field
excitation.

Instead of using definite polar projection for the three-phase
bipolar exciting winding, as shown in Fig. 141, we could use a
distributed winding, like that in an induction motor, placed in
the same slots as the inductor-alternator armature winding. By

FIG. 141.—Inductor alternator with three-phase excitation.
placing a bipolar short-circuited winding on the inductor, the
three-phase .exciting winding of the high-frequency (24-polar)
inductor alternator also becomes a bipolar induction-motor
primary winding, supplying the power driving the machine.
That is, the machine, is a combination of a bipolar induction
motor and a 24-polar inductor alternator, or a frequency
converter.
Instead of having a separate high-frequency inductor-alter-
nator armature winding, and low-frequency induction motor
winding, we can use the same winding for both purposes, as
shown diagrammatically in Figs. 142 and 143. The stator
winding, Fig. 142, bipolar, or four-polar 60-cycle, is a low-
frequency winding, for instance, has one slot per inductor pole,
that is, twice as many slots as the inductor has teeth. Successive
turns then differ from each other by 180° in phase, for the high:
frequency inductor voltage. Thus grouping the winding in