100 SYNCHRONOUS MOTORS 



if we substitute for 2, its value, 



we have 



P2=I<2.Iw, 



as before. 



Second Application. Operation with Constant Excitation, on 

 Constant-Potential-Supply System. When once the V-curves have 

 been drawn it is very easy to obtain from them the different load- 



V 



FIG. 49. 



values corresponding to any given constant excitation. These values 

 can also be determined directly from the diagram in the following 

 manner: 



Let us take the reactive current I d and let us find the active current 

 I u corresponding to each value thereof. The direction A 2 D (Fig. 49) 

 being, therefore, constant, can be drawn once for all. Likewise, the 

 direction A 2 W, to which the reactive segments DA\ are parallel, makes 



