250 



ELECTRICAL MACHINERY 



armature m.m.f. would still be of a magnitude equal to OC 

 but its direction would be behind that of OC, as shown 

 at OC', of Fig. 154. Again the angle YOC' is equal to $. 



Coils and vectors in dotted lines show 

 conditions for a fraction of a revolution 

 later than those shown by full lines. 



FIG. 153. Armature Reaction in Two-phase Alternator, Current in 

 Phase with Generated e.m.f. 



Reaction of a Three-phase Alternator. The student 

 may construct for himself the diagram for a three-phase 

 alternator, and will find that this machine, like the two- 



FIQ. 154. Armature Reaction in Two-phase Alternator, Lagging 

 and Leading Current. 



phase machine, gives a non-pulsating armature reaction. 

 The magnitude of the reaction depends upon the magnitude 

 of the armature current and is equal to 1.5 multiplied by 



