10 ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 
value is the watt component, represented by the line AP, 
while the length OP is the excitation value. 
442, Other Points on Curve.—With the simple determin- 
ation of the regulation, say, for an armature current corre-. 
sponding to the normal load, to a normal voltage and to 
cos ¢=1, we have fixed one point of the line PP’ as well as 
one point of the V characteristic and, therefore, it is a 
simple matter to find other points. 
The various values of the lines AP and AP" can be easily 
converted into amperes by means of Equations (30) 
to (82). 
443. Actual Results Obtained.—In Fig. 94, the graphical 
method is developed for the 450 H.P., 3500-volt star con- 
nected armature, where the normal watt components 
450 X 746 
will have the value of C,, cos P=T73%3500% 9477 09-5 am- 
peres, the efficiency being equal to 94 % and the corre- 
sponding field excitation 6300 ampere turns, as found by 
the graphical determination of the regulation. The current ~ 
value of the 59.5 amperes, plotted above 6300 ampere 
turns, gives one point of the V characteristic. 
444, Determination of Other Points.—Further points 
on the V curve may be found in the following manner: 
Having obtained a point P, by applying the graphical 
method of determining the regulation, one has simply to 
draw a line through this point P parallel to the abscissa 
line OO: and erect another triangle on the line OA so that 
the point P1 falls on the parallel line. The length OP! will 
now represent the value of the field excitation, and the line 
AP! indicates the ampere turns which correspond to the 
armature current on short circuit. 
445. Results of Complete Graphical Method.—Make 
OP! = OB, the length BC = AP‘ and draw the perpendic- 
ular CD until it cuts the R® curve at D. Mark the line DB 
and draw a parallel to it, the line HR, through the point R; 
