 —S—————— << so Ul Erm OO 
ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 75 
~The reason for this is, that the rule does not take into con- 
sideration, that the states of saturation are different, when 
the armature earries a short circuit current and when it 
delivers the same current to an external circuit at a high 
voltage. This is due to the fact, that the leakage con- 
ditions are generally more unfavorable in the case of a 
highly saturated magnetic circuit, than that of low satura- 
. tion corresponding to the short circuited armature. 
130. Second Method of Determining Voltage Drop.— 
The second method of determining the voltage drop from 
the open circuit and short circuit characteristics, takes 
into account the different degrees of magnetic saturation 
and leads to such rules which will enable the designer to 
ealeulate the machine characteristics with exactness, 
besides enabling him to fix the amount of regulation to 
be expected. The rule as it has been developed is embodied 
in the following equation: 
gy 5 RY 
gery 7 yun 
where A,, A, and A,, have the same meaning as stated in 
a ta 2 
Par. 126 and the factor(#*) represents the ratio between 
the apparent resistances which correspond to the -open 
circuit voltage of the load E. M. F. and to the non-exeited 
state. 
151. Determination of Inductive Regulation.—Equa- 
tion (17) leads to a simple method of determining the 
inductive regulation of an alternator. 
In this and Paragraph 132, the test data of the 235 KVA. 
three-phase generator, Fig. 34, is used. Fig. 37 gives the 
no-load and the short circuit characteristies together with 
the curve R?, which represents the square of the apparent 
magnetic resistance in terms of the excitation current. 
eRTY OF ELECTRICAL LABORATORY, } 
“pie CULTY OF APPLIEO SCIENCE. 
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