ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 165 
3.6 X 10° 
2X 61 
which is a satisfactory figure. 
This preliminary calculation indicates clearly that the stamp- 
ing at our disposal is so far suitable for the present ease. 
density will be = 35,300 lines per square inch, 
309. Field Winding Space.—We have now to see, if, for the 
specified conditions of regulation and for the assumed 
armature ampere turns, the corresponding field ampere 
turns will have the necessary space. As already pointed 
out, the bore of the machine is somewhat smaller than the 
usual value, and as the somewhat stiff condition of voltage 
drop requires a larger ratio between the armature and 
field ampere turns than the average one, it is not at all 
certain that the winding space is large enough. To check 
this, it is necessary to make several assumptions and cal- 
culations, which are afterward to be modified if not found 
* eorrect. 
310. Section of Pole Core.—First of all, it is necessary to 
design the pole core section such that its saturation shall 
produce the essential knee or bend in the open circuit 
characteristic curve. In considering that the voltage drop 
is to be small and that the power factor is as high as 0.85, 
it is necessary to drive the saturation of the poles some- 
what higher than usual, which aifords at the same time, 
from a mechanical point of view, the advantage that the 
width of the pole will be diminished, besides affording 
more space for the winding. 
The pole density should be fixed at about 105,000 lines; 
hence, if we assume a leakage factor © of 1.3, the neces- 
1,3°X% 3:6. x 10° 
105,000 baat ia 
44 § ; 
12x06 3.85 inches, 
which we make, for convenience, 3.75 inches. 
sary effective section is equal to 
square inches; and the pole width is 
