ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 199 
386. Section of Armature Core.—In calculating the arma- 
ture core section, particular care must be taken that the 
total height of the armature laminations should not be 
less than one-half of the pole pitch or pole are, as with a 
small height of laminations the variable magnetization 
would reach the solid iron yoke and produce an excessive ~ 
iron loss. 
In the present case we fix the total height of the laminations 
in the armature at 5 inches, with a density of 
2.9 x 10° 
29.75 X 3.14 
8 
= 46,000 lines per square inch. 
x 6x .9 
387. Particulars of Yoke.—tThe sectional area of the arma- 
ture yoke may be expressed with sufficient accuracy as 
33 X 3.14 2.9 x 10° : 
follows: Ting ages b= 26x60 = eae Mk and if we allow 
y 
a density of By = 46,000 lines per square inch, b, the 
2 X 10° 
46,000 X 26 
height of the cast iron yoke, will be equal to 
- == 2.4 inches. 
The length of the magnetic path in the yoke will be in- 
fluenced by the space required for the projecting parts of 
the armature coils and for the central magnetizing coil. 
An allowance of 6 inches on account of the two armature 
eoil ends and 3 inches for the field coil width, will be a 
good approximation and, if necessary, it may be altered 
later. 
388. Section of Pole Projection.—When designing the iron 
wheel it is necessary to assume the value of the leakage fac- 
tor as a moderate figure. Calculating with © = 1.10, the 
flux passing through a pole projection will be 2.9 X 1.1 X 
10° = 3.2 x 10° lines. Assuming a density of 75,000 lines 
. pert 3.2x 10° 
per square inch the necessary section is equal to F5.G00" 
_ == 42.5 square inches. - 
