74 ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 
field excitation, is 6,500 volts, so that the drop is equal to 
6,500 — 6,000 = 500 volts. The actual voltage drop of 
the alternator in question has been found to be 1,200 volts, 
which is much more than the theoretically determined 
figure. 
Take another value of field excitation, say 10 amperes, with 
an open circuit voltage of 3,300 volts. The test. in this 
instance gave a voltage drop of 1,500 volts with 26 amperes 
inductive load on the armature, which is very close to the 
ealeulated figure, namely 1,800 volts, corresponding to 
10 — 5.06 = 4.94 amperes excitation. 
129. Consideration of Saturation.—In Fig. 36, as in other 
examples, it will be observed that the above method gives 
good results, when applied to that part of the open circuit 
4 
IN 
\ 
N 
L|_ YZ 
: 
8 
y 
TT ae 
(7) - 400 750 
EXCITATION CURRENT IN AMPS. 
Fig. 36.—CHARACTERISTICS OF A 1,850 KVA., 50-CycLE, STAR 
CONNECTED 3-PHASE ALTERNATOR. 
= 
8 
- 
TERMINAL PRESSURE IN VOLTS. 
a 
og 
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3 3 
SHOT CIRCUIT CURRENT LN AMPS. 
8 
characteristic which is under the knee or bend of the 
curve, but when applied to the curve above the bend, it 
produces values of the drop which are too small. 
