ELECTRICAL APPARATUS

safe construction, at 25 cycles to get a good power-factor at
moderate speed, from a straight series motor, even if such a
design as discussed above were not inoperative, due to excessive
distortion and therefore destructive sparking.

Thus it becomes necessary in the single-phase commutator
motor to reduce the magnetic flux of armature reaction, that is,
increase the effective magnetic reluctance of the armature far
beyond the value of the true magnetic reluctance. This is ac-
complished by the compensating winding devised by Eickemeyer,
by surrounding the armature with a stationary winding closely
adjacent and parallel to the armature winding, and energized by
a current in opposite direction to the armature current, and of
the same m.m.f., that is, the same number of ampere-turns, as
the armature winding.

FIG. 156.—Circuits of single-
phase commutator motor.

FIG. 157.—Massed field winding and
distributed compensating winding.

191. Every single-phase commutator motor thus comprises a-
field winding, F, an armature winding, A, and a compensating
winding, C, usually located in the pole faces of the field, as shown
in Figs. 156 -and 157. .
The compensating winding, C, is either connected in series (but
in reversed direction) with the armature winding, and then has
the same number of effective turns, or it is short-circuited upon
itself, thus acting as a short-circuited secondary with the arma-
ture winding as primary, or the compensating winding is ener-
gized by the supply current, and the armature short-circuited as