188 -ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 
Allowing 0.06 inch micanite slot insulation, 0.02 inch for 
play and a suitable amount for any irregularity of the 
stampings inside the slots, it will be found that a slot 
of 0.85 X 1.85 inches will be ample for the 6 conductors, 
each composed of 6 parallel connected No. 9 S.W.G. wires, 
assuming a current density of 1,900 amperes is square 
ineh, see Fig. 83. 
The total number of slots being 144, the slot pitch is equal to 
87.5 xX 3.14 
144 
tooth is equal to 1.91 — 0.85 = 1.06 inches, while the mean 
thickness is 1.1 inches. 
= 1.91 inches and the narrowest part of a 
361. Length of Armature.—From the basis of the magnetie 
density in the teeth, we optain an armature iron length 
3.7 X 10° : 
of 68 = 13.2 inches, corresponding to 
70,000 xX L$ 5 ee EH 
a flux value of 10° X 2,800 = 2.2 x 60 x 576 X F.,, where 
F, = 3.7 X 10° per pole. 
With the additional 10 per cent. for the paper insulation 
and 1 inch for two ventilating ducts, the overall length 
of the armature will be 15.5 inches. 
According to Fig. 26, the saturation of the armature core 
should be about 30,000 lines and with an iron height of 
4.4 inches above the slots, a density of 32,000 lines per 
square inch is obtained. 
362. Particulars of Pole System.—In designing the pole 
section, we assume an average leakage factor 9 of 1.30, 
that is, the field flux is taken equal to 4.8 X 10° lines, and 
with a pole core density of 105,000, the sectional area will 
be EHO = 45.7 square inches. 
_Allowing 1.25 inches for the useful leakage, the length of 
the core is 14.25 inches and, therefore, the pole width 
