170 
ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 
8 
For the factor we find a value of 1 + eS ee Wet = tare 
say, 12—k,. That is, for the eo armature current 
= 17,500 _ 
which represents a back ampere turn value of “7a 
1,450 per pole, the corresponding excitation will be equal 
to 1.2 x 1,450 = 1,740 ampere turns. The straight line 
through the zero and this particular point, B, represents 
the short circuit characteristic, see Fig. 77. 
ENTCALIW LW AUPERE TURMS. 
2000 4000 6000 
‘ 
—T : 
N 
% 
N 
J) 
: 
TERUIWAL PRESSURE IN VOLTS. 
\ 
; 
~ 
/ \\ 
\ \ 
N 
\ 
\ 
SHORT CLRCUI: 
/ 
ad. 
Z 
7 
‘ 
/ 
A 
/ 
; Pi! Ys.) as 
: 
\ / fi 
V ae 3 
~, / 
A \ A 
~ , 
e ~ 
/ 4 
7 oye 
Ws-f---7 
Fie. 77.—CHARACTERISTICS OF THE 175 KVA., 400 REVsS., 
40-CYcLE, 3-PHASE ALTERNATOR. 
319. Calculation of Drops.—In Fig. 77, the application of 
the graphical method in determining the non-inductive 
and cos P = 0.85 full load voltage drops, gives satisfac- 
tory results. 
