ALTERNATORS. 



233 



assumptions has already been shown not to be accurate, 

 since the lagging current decreases the main field and reduces 

 this voltage. The curve of voltage oblained' from the 

 diagram will consequently be higher than its actual position. 

 The curve II. in Fig. 109 is the curve obtained from the diagram 

 and illustrates at once the fact that the characteristics 

 obtained with inductive loads are nearly straight lines, owing 

 to the voltage lost in armature impedance being much more 

 nearly in phase with the terminal voltage, and thus producing 

 almost a direct drop in voltage proportional to the load 

 current of the alternator. 



FIG. 110. CALCULATION or EXTERNAL CHAKACTKRISTIC INDUCTIVE LOAD. 

 Cos <f> = -8. 



C D = Armature and line drop. 

 D B = Terminal volts. 

 A B = Total volts generated. 

 A C = Reactance voltage. 



Phase Difference between Total Volts and Load Current with 

 Non-inductive Load. From the discussion of the two pre- 

 ceding experiments it is evident that, even when working 

 on a non-inductive circuit, the phase difference between the 

 current and the total voltage generated in the armature of 

 the alternator will vary considerably with a varying load. 

 This is perhaps brought out most clearly by the diagram 

 Fig. 1 08, where the line A B represents the total armature 



