ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 49 
sity in the teeth is almost double of that in the armature 
core. 
89. Limits of Densities.—The difference in the limits of 
densities is due-to the increasing or driving up of the in- 
duction in the teeth, which reduces the necessary section 
under the pole shoe and leads to an economical design and, 
besides, it stiffens or produces a more stable magnetic field 
next to the periphery. 
red 
ZEVBUTIES IW LIMBS PER SARE ICH 
i 2 eR ee eS. 
[ 
/ 
40 0 30 No $0 €0 70 80 Go 00 MO fo 
NUMBER OF FREQUENCIES PER SECOND 
Fie. 27.—AVERAGE TEETH DENSITIES FOR DIFFERENT FREQUENCIES. 
The same reasoning does not hold good for the armature core 
section, for it is necessary to choose and fix the magnetic 
densities in such a manner, that the resulting iron losses 
shall not exceed a certain limited amount, in order to ob- 
tain the best commercial efficiencies for different sizes of 
generators. As a good average figure, it may be noted 
that in standard designs the loss in the armature stamp- 
