204 GENERAL DIAGRAMS FOR SYNCHRONOUS MOTORS 



proportional to dD=ZI d and measured along the reference-line BY; 

 and if the corresponding reactive currents, Id, be represented by other 

 segments proportional to DC=ZId', then the locus of the point C, at 

 the end of the segment DC, is a right line, QP, whose angular coefficient 

 with respect to the point Q as a pole is 



DC xkn 



(30) 



This coefficient depends only on the field and armature windings. 

 The right line QP is easily drawn, in practice by determining the points 



Q and P which correspond, respectively, to zero-lag and zero-load: 

 we have 



For the point P, 



For the point Q, 



I d =o 



\ 2 



Hkn 





For each value of e there exists a value of A A d . This value is obtained 

 from the characteristic curve (Fig. 16), by drawing, from the point 

 m, corresponding to this coordinate, the right line ma, making the angle 

 /I with respect to the axis of A values, the angular coefficient of this 

 line being the resistance of an average turn of the shunt winding, 



tan d=r. 



