oil lying _between_ the two
coils with which it is in series. The phase of the heavy line currents
was shown in Fig. 4 to lie between the other two. Therefore, in the
armature in Fig. 6 (or 8) there will be six phases, while in Fig. 5
there are only three, the number of leads (three) remaining the same
as before. This is the fundamental principle of this ingenious
invention. To have six phases in Fig. 5 would require six leads, but
in Fig. 6 precisely the same result is obtained with only three leads.
In the same way the three leads in Fig. 6 might again be combined and
passed around the armature again, and so on forming still more phases,
without increasing the number of leads. Figs. 7 and 8 compound with 5
and 6 and show the same system for a Gramme ring instead of a cylinder
armature.

As was stated in the early part of this description, the main object
in a rotary current motor is to have a magnetic field which is as
nearly constant in intensity as possible, and which changes only its
position, that is, its axis. But in Fig. 4 it was shown that the
current I (in dotted lines) is greater than the others (about as 1.4
to 1 for a phase difference of 90 degrees). If therefore the coils in
Fig. 6 or 8 were all alike, the magnetism generated by the heavy line
coils would be greater than that generated by the others, and would
therefore produce very undesirable pulsations in the magnetic fields;
but as the magnetism depends on the ampere turns, it is necessary
merely to have correspondingly fewer turns on these coils, as compared
with the others. This is shown diagrammatically in Figs. 6 and 8, in
which the heavy line coils have less windings than the others. In
practice it is not always possible to obtain the exact ratio of 1 to
1.4, for instance, but even if this ratio is obtained only
approximately, it nevertheless reduces the pulsations very materially
below what they would be with half the number of phases. It is
therefore not necessary in practice to have more than an approximation
to the exact conditions.

[Illustration: FIG. 9.]

[Illustration: FIG. 10.]

[Illustration: FIG. 11.]

[Illustration: FIG. 12.]

Fig. 9 shows a multiple phase armature having double the number of
phases as Fig. 1, and would according to the old system, therefore,
require eight leads. Fig. 10 shows the new system with the same number
of phases as in Fig. 9, but requiring only four leads instead of
eight. Figs. 11 and 12 correspond