REGULATING POLE CONVERTERS

425

position by having a slot in the field poles, as indicated in dotted
line in Fig. 196 and Fig. 198, B. With the arrangement in Figs.
196 and 198, this is not feasible mechanically, and these arrange-

FIG. 200.—E.m.f. variation by shifting-flux distribution.

ments are, therefore, unsuitable. It is feasible, however, as
shown in Figs. 199 and 200, that is, when shifting the resultant
magnetic flux electrically, to leave a commutating space between

FIG. 201.—Variable ratio or split-pole converter.
the polar projections of the field at the brushes, as shown in Fig.
200, and thus secure as good commutation, as in any other com-
mu bating machine.