106 
ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 
percentage of same, the sectional area has to be caleulated 
as the mean value of the top and bottom. sections of the 
teeth. In this particular case the difference is insig- 
nificant. 
ARMATURE CorE RELUCTANCE: The armature core offers a 
section of 6.14 x 5.5 * .9 = 30 square inches and a picnee 
v of 5.5 inches. 
1.34 10° 
2X30 
= 22,400 lines per square inch and the corresponding 
ampere turns per unit length are 4, making the total 
number for the armature core equal to 5.5 4= 22 
per pole. 
The magnetic density in the sheet iron is equal to 
Arr Gap Retuctance: In ealeulating the leakage factor, 
the air gap reluctance has been already found equal to 
26 
lo! xX 1.34 x 10° = 
To = = and from which r, X F, = 
3,480 ampere turns. 
Total AMPERE TURNS PER PoE: The five distinct magnetic 
paths require, in all, a total number of ampere turns 
amounting to 4,310 per pole, when the generated E. M. F. 
of the armature is 3,000 volts. 
By following up the same course of calculation for three 
other degrees of saturation, the curve of the open cireuit 
characteristic is obtained. 
The systematic arrangement of the various data and results, 
Table 15, will be found very useful, as indicated in the 
present example. 
Cuaracteristic Ratio: In Fig. 61, the E.M. F. is plotted 
in terms of the corresponding ampere turns. The follow- 
ing remarks on the form of this open circuit characteristic 
are based on the caleulation of the apparent magnetic 
resistance curve. 
