THE CONTINUOUS CURRENT GENERATOR 121 



ing current. In this figure a minus sign in the conductor 

 cross-section signifies that the current is away from the 

 observer, and those conductors with a plus sign are carry- 

 ing current toward the observer. The main field is sup- 

 posed absent in this figure. 



That the armature winding does give a field as shown in 

 Fig. 75 may be seen by supposing conductors 1 and 2 to 

 form one turn of a solenoid; conductors 40 and 3 to form 

 another turn, etc. Thus, each conductor may be imagined 

 as connected with one on the opposite side of the armature 

 and the turns so formed all give an m.m.f. in the direction 

 shown by the field in Fig. 75. 



FIG. 75. Magnetic Field Produced by Armature Coils alone. 



Distortion of Field by Armature M.M.F. In Fig. 76 is 

 shown the field produced by the resultant m.m.f.; this 

 resultant m.m.f. is obtained by combining vectorially that 

 of the main field with that of the armature. In combining 

 quantities vectorially the quantities are represented by 

 lines drawn from a point in the directions of the quantities 

 and of a length proportional to their value. The diagonal 

 of the parallelogram drawn on these two lines as adjacent 

 sides thus represents the resultant effect of the two. 



If the machine is a generator, the main field is twisted 

 in the direction of rotation of the armature as shown in Fig. 



