110 ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 
rod 
For this particular case r, has been already determined and 
found to be equal to “= — ee 
ArMATURE LEAKAGE RELUCTANCE: The expression of the 
armature leakage reluctance is 
mat 0.313 
2 4XtXlxo ,4xtxr(a+n+o) : 
s\n+a) (a+n)o A ORESAT, 
which gives in the present example a value of 
rag pe 0.313 
* 4X 2.16 X5.5 X 2.08 , 4 2.16 X 1.33(8.3+4+2.08) | 
0.75X8.3 ye 8.3X 2.08 Tee 
0.313 _ 78.5 
~16+74+17 10°’ 
from which the factor k, is equal to 
k. .= 14 25 = 1.33; 
1,000: 
that is, each 1,000 ampere turns of the field produce —~; 33 
= 750 ampere turns on the short circuited armature. 
UseruL Ruutes: If the number of armature turns are given, 
it is very simple to obtain the value of the short circuit 
current, or, if a certain short circuit current be given, to 
ealeulate the corresponding field excitation. 
AMPERE TURNS PER PoE: In this particular ease, the 
normal armature current 62.5 amperes would produce a 
M. M. F. of 1.41 x 62.5 x 64 x 15 = 84,500 total ampere 
turns; this requires, on short circuiting, a total field 
M.M.F. of 1.33 x 84,500 = 112,000, or) = 1,70. 
- ampere turns per pole. 
Suort Crrcuir CHARACTERISTIC: If we now fix the point B,. 
by erecting the normal armature current as an ordinate, 
from the corresponding field ampere turns as abscissa and 
