198 ALTERNATING GENERATORS AND SYNCHRONOUS: MOTORS. 
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383. Space Factor.—Regarding the space factor, the copper 
section inside a slot is equal to 44 x 0.01057 = 0.465 square 
inch, and the sectional area of the slot is 1.75 square inches, 
which results in a space factor of = 0.265. 
384. Value of Useful Flux.—The normal value of useful 
flux will be found by means of Equation (33); 2,300 = 
1.6 x 70 x 44 X16 X 2X F, where F, = 1.45 x 10° lines, 
providing that the field system is of the alternate pole 
type, but as the coils leaving a pole enter the air and from 
there, so to speak, come again under a pole of same 
polarity, the flux per pole projection in this particular 
design is equal to 10° X 2 x 1.45 = 2.9 xX 10° lines. 
Fie. 88.—Stort Winpine or 55 KVA., 1,050 R.P.M., 70-CrciE, 
SINGLE PHASE ALTERNATOR. 
385. Armature Length.—The iron length of the armature 
is determined by fixing the permissible saturation of the 
teeth, with regard to their losses. As the teeth pass 
through a variable field of 2.9 x 10° to 0 lines of magnetie 
flux, we will allow a density of 80,000 lines per square 
inch. 
Therefore, the length of the effective iron is equal to 
2.9 X 10° 
“g0,000 —! xX 2965 %.3 = 6.10'¢, 
where 1 = 5.4 inches per armature half. An additional 
0.6 inch must be allowed for the paper insulation between 
the laminations. 
