262 



ELECTRICAL ENGINEERING 



OM a = 



OM = 



OEi"= EI" = E b =jlx = e.m.f. consumed by the armature 



reactance x in quadrature ahead of 7. 



OEi = EI = E + 7 (r + jz) = e.m.f. generated by rotation, 

 that is, the e.m.f. generated by cutting the flux 

 produced by the resultant of the m.m.f. 's of field 

 and armature. 



M a = m.m.f. of the armature current. 

 M resultant of field m.m.f. and armature m.m.f. in 

 quadrature ahead of the e.m.f. EI produced by it. 

 OMf = M f = field m.m.f. 

 OE Q = EQ = e.m.f. generated in the armature at no load, in 



quadrature behind the field m.m.f. 



The no-load e.m.f. can be separated into two components OEi 

 and OE 2 . 



OEz = E 2 = jlx' = e.m.f. consumed by armature reaction, in 



quadrature ahead of 7. 



If the two reactance drops Ix and Ix f are combined the diagram 

 may be simplified as shown in Fig. 239. 



FIG. 239. 



OE = E = terminal e.m.f. 



01 = I armature current lagging by angle <f>. 



OE Q ' = EJ = Ir = armature resistance drop in phase with 7. 



OE Q " = EQ" = jl (x + x') = jlxo = synchronous reactance drop 

 in quadrature ahead of 7. 



OEo'" = EQ" = Iz = synchronous impedance drop. 



OE Q = E Q = EQ + 7z = e.m.f. generated at no load. 



OMf = M f = field m.m.f. in quadrature ahead of E Q and pro- 

 portional to it, neglecting the effect of saturation. 



