3-B] 



PREDETERMINATION. 



95 



is a maximum. The armature current will likewise be a maximum, 

 if it is in phase with this electromotive force. In this position, the 

 flux set up by the armature current has a cross-magnetizing effect; 

 the flux passes transversely through the pole piece but does not pass 

 through or link with the field winding and so does not directly oppose 

 the field ampere-turns. 



Fig. 10 shows the armature conductors midway between poles; the 

 coil, to which these conductors may be assumed to belong, is exactly 

 opposite a pole. In this position the electromotive force induced in 



FIG. 9. Distortion of field by 

 transverse magnetization, or cross- 

 magnetizing effect of armature cur- 

 rent ; produced by an in-phase cur- 

 rent, or component of current. 



FIG. 10. .Weakening of field by de- 

 magnetizing effect of armature current ; 

 produced by a wattless or quadrature 

 current, or component of current. 



the armature conductors is zero; at zero power factor the armature 

 current lagging 90 behind the electromotive force is a maximum. 

 It will be seen from the figure that in this position the armature has 

 the greatest demagnetizing effect, the flux produced by the armature 

 passing through the field winding and directly opposing the field 

 ampere-turns. 



46. It is seen that when the armature current is in phase with the 

 generated electromotive force it produces distortion and cross-mag- 

 netization; when the armature current is in quadrature it produces 

 demagnetization without distortion, the armature ampere-turns being 

 in direct opposition to the field ampere-turns. 



When the current has a phase displacement, with respect to the 

 induced electromotive force, between o and 90, it may be considered 

 as composed of two components, an in-phase component producing 

 cross-magnetization and a quadrature component producing demag- 

 netization. 



47. On short circuit, the current in the armature lags 90 (or 



