SYNCHRONOUS MACHINERY 



261 



The total reactance of the armature XQ is called the synchronous 

 reactance and consists of two components, x which represents the 

 effect of the armature leakage flux and which has been called the 

 armature reactance and x' which represents the effect of armature 

 reaction. 



The quantity ZQ = r + J^o is the synchronous impedance of the 

 armature and consumes a component of the no-load e.m.f. Iz = 

 I (r + jx ) which is the synchronous impedance drop in the 

 armature. 



Thus the e.m.f. generated at no load is the vector sum of the 

 terminal e.m.f. and the synchronous impedance drop 



156. Vector Diagram of E.M.F.'s and M.M.F.'s. In Fig. 

 238 is drawn the vector diagram of an alternator supplying an 

 inductive load. 



g 



' 



FIG. 238. 



OE 

 01 



= E 

 = I 





OE' 



= terminal e.m.f. 



= armature current lagging behind E by angle $. 



= Ir = e.m.f. consumed by the armature resistance 



r in phase with I. 

 = E + Ir = resultant of all the e.m.f. 's generated 



in the armature. 

 E b = jlx = e.m.f. generated in the armature by the 



leakage flux fa, produced by the armature current. 



