176 ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 
going assumptions, we have found that the total number 
of armature ampere conductors will be 346 X 216 = 74,600 
and, allowing a peripheral density of 500 ampere con- 
ductors per inch, the approximate value of the bore is 
equal to a ae — 47.5 inches. If the diameter of the 
wheel, Fig. 78, is fixed as 47 inches, then the peripheral 
speed will be 4,600 feet, which is a good average value. 
335. Dimensions and Shape of Slots.—The dimensions 
of the slots and their shape are to be so designed that a 
high space factor may be obtained. With regard to the 
size of conductor, we assume a current density of about 
Fig. 79.—Stor WINDING, 300 KVA., 500 Voit, 3-PHASE ALTERNATOR. 
2,000 amperes, so that in the present case, & sectional area 
¢ 348 
°F 2,000 
Each slot has to receive 3 conductors; therefore, it will be 
best to use several wires in parallel, to make up a con- 
ductor. It is found that 7 No. 7 8.W.G. round wires give 
the most satisfactory result, as regards the current density 
and slot shape. ; 
A slot with the dimensions of 0.75 inch in width and 1.75 
inches in depth, takes the 21, No. 7 S.W.G. wires, the 0.05 
inch thick micanite insulation, and leaves a margin on 
account of the uneven assembling of the stampings, as 
well as a certain play for the former wound coils. 
= 0.173 square inches is required. 
