ALTER* ATUR RMU'LATin* AND OPERATE >\ 



157 



The value of the angle a may be found by first finding the 

 angle 0. 



sin/8 



Fsin 

 V, 



a = - 



a is usually so small that it may be neglected. 

 Tin* vector I-\ leads I" by (90 a) degrees, but a is so small 

 that it may be neglected. The armature reaction vector A 

 is 180 from the current vector. By geometry the angle between 

 -A andFi 



X = 180 - (90 + 0) 

 = 180 - (90 + 6) nearly 

 = 90 - nearly 



">H. Vector diaKr:ini of m.-mnetomntive lorn- method. hmnin ^ current 



By the cosine law, 



F 2 = F! 2 + A 2 - 2F } A cos (90 + 9) (43) 



Tin- voltage /-.' eonv-ponding to /' and found from the satura- 

 ion Clirve, Tiir. l.")7. i> thr no-loa.l voltage of the generator. 



T:ik<- tin- i-xMinpIr (if the preceding parnni .'ipli. 'I'll' 

 MM'tlmd will first he used. Tin- iiun-limr will l)c considered ;is 



Tin- roil VoltM^e ? - 1,330 v 



V3 



i h //,' dn, P b :;70 X 0.09 - 33.8 volts. 

 cos $ - 0.85 



l'i - \/[(l,3:) xo> j ; + [!.:;. ;:,9 volte. 



