Abstract :
This paper deals with modifications of the Leblanc phaseadvancer in which the compensating effect of the phase advancer can be varied, within wide limits, without changing the speed of the phase advancer. The first modification is that of providing two sets of brushes on the commutator of the standard Leblanc phase-advancer, as in the Schrage motor. The compensating effect of the phase advancer can be varied by altering the angle between the brushes. This modification has certain objectionable features and is not considered desirable. In the second (and best) modification the phase advancer is provided with a stator and a stator winding, and the latter is closed through a rheostat. The compensating effect of the phase advancer is increased or decreased by decreasing or increasing the resistance in the circuit of the stator winding of the phase advancer. The third modification is to provide a commutator winding and a slip-ring winding on the rotor, and to close the latter through a rheostat. The compensating effect of the phase advancer is increased or decreased by increasing or decreasing the resistance in the circuit of the slip-ring winding of the phase advancer. The fourth modification, a combination of the two preceding ones, is rather complicated and does not offer any special advantages. It is easily made available, however, being essentially the same as the Schrage motor, and is useful for the study of the second and third modifications. The results of an experimental study of the second and third modifications, made with the help of a Schrage motor, are given. The theory of the Leblanc phase-advancer with stator winding and additional rotor winding is worked out with the help of vector diagrams and equivalent circuits. The method of predetermining the current locus and the performance curves of a motor connected to either type of phase advancer is given and is applied to a 150-h.p. motor.
