Abstract :
V. Karapetoff: An impression may be gathered from the paper that the power factor of the motor is improved because the squirrel-cage winding is highly inductive. It seems to me that the squirrel-cage winding necessarily has to be highly inductive so as not to interfere with the series characteristics of the motor at the start. If it were not for an additional mechanical complication (Fig. 2), it would be better to make this winding less inductive at and near synchronism. A transformer diagram at constant current will readily show that the common flux is lagging behind the primary current at a non-inductive load more than at an inductive load. Therefore, the less inductive the squirrel-cage winding, the more the flux φf is lagged behind I (Fig. 4). But the flux in T must be in time quadrature with φf in order that the total e.m.f. between the brushes be equal to zero. Therefore, lagging φf also causes φt and Et to lag more behind I; in other words, it causes the vector of the current to come nearer that of the total voltage E. Thus, the power factor is improved even though the squirrel-cage winding has a high inductance, and the power factor would be improved more, if it were advisable to reduce the inductance of this winding in normal operation.
