16 
ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 
slotsis equal to — =6.45 inches; or, with a value of 
6.4 inches, the overal diameter of the armature will 
be 63 + 2(2.1+6.4)= 80 inches. 
463. Pole Core Area,—For the first approximation we will 
assume a leakage factor of ¢=1.2 so that the flux per 
pole will be equal to 1.24.2 10®=5.05 x10® lines. 
With regard to the reasons developed in Par. 439, the 
magnetic density in the pole section should not be 
higher than about 95,000 lines per sq. inch. The 
effective area of the pole core under these conditions 
will be ene =53 sq. inches. 
Allowing for the useful magnetic leakage, we take an 
overall length of 12 inches, and the width of the pole 
53 
ee kes Te. setae 
12x 0.95 4.65, say 4,75 inches 
stamping will be 
464. Wheel Rim.—The material of the wheel rim is cast iron; 
465. 
so with regard to mechanical strength as well as the . 
moderate saturation degree, the section of the same 
will be taken as 20 by 4 inches. Therefore the sectional 
area is equal to 20x4=80 sq. inches and the magnetic 
density i ne _ =31,600 lines. 
Armature Ampere Turns.—tThe air gap should be 
chosen with the view that the overload capacity, or, in 
other words, the ratio between the short circuit current 
which corresponds to the normal excitation, and the 
normal load current of 72.5 amperes, should be about 
1.8 to 2 
For the normal load of cos p= 1, the total number of arma- 
ture ampere conductors is equal to 1,248 x 72.5=90,000.. 
Therefore, the total number of armature ampere turns 
wor = 45,000, or 20,000 =15,000 ampere 
_ turns per phase... 
is equal to 
es 
