Theory of the brush-shifting A-C motor — IV: Speed control with power-factor correction

The preceding papers of this series presented an analysis of the brush-shifting a-c motor. Parts I and II dealt with the case when the voltage introduced into the stator coils from the commutator was collinear with the voltage induced in the stator coils by slip. Part III dealt with the case when the voltage introduced into the stator coils from the commutator was in quadrature with the induced voltage. This paper extends the earlier analysis to include all the possible phase positions of the voltage introduced into the stator coils from the commutator. Under these conditions power factor and speed are controlled simultaneously. Methods for constructing the circle diagram for these conditions are given, and the characteristics of the motor predicted from the circle diagram are compared with the characteristics obtained by laboratory tests.