GENERAL DIAGRAMS FOR SYNCHRONOUS MOTORS 179 



corresponds to the approximately constant loss produced by the 

 " no-load " active current, in consequence of friction, resistance, 

 hysteresis, and eddy currents. The part /o will De called the " active 

 current for zero-load." The other part, represented by Dd, corre- 

 sponds to the energy of the useful secondary current, and which is 

 proportional to the said current. 



FIG. 3. 



Fundamental Equation. The fundamental equation connecting 

 , E, and the active and reactive currents can be written directly 

 from Fig. 2. The triangle OBC gives, in fact, 



In this case we have 



(Z7) cos 0= projection of BC on OX 



= (proj. of .BD+proj. of DC) on OX 

 = (proj. of OH" + proj. of BH) on OX 

 = 7.1 w cos f+ZId cos0 

 = ZI W cos +ZId sin . 



Substituting this value, and remembering that / 2 =/ to 2 +/d 2 , we 

 have, from (a), 



). . . (i) 



