4 ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 
- struction Book, the peripheral speed of the magnet wheel, 
neglecting the small difference existing between the arma- 
ture bore and the external diameter of the magnet wheel, 
that is, the airgap. 
284. The maximum allowable current density for the armature con- 
ductors being fixed at 2,000 amperes per square inch, 
calculate the necessary conductor section and state the 
most suitable 8. W. G. size for same, but do not employ 
thicker wire than .16 inch diameter (bare). Calculate also 
the resulting total number of wires to be placed in a slot- 
285. Determine the most suitable slot shape, taking into considera- 
tion the ‘‘good ratio” of slot width to slot depth, and give a 
dimensioned sketch, showing the arrangement. of the 
wires. Micanite insulation of .06 inch thickness and a 
fixing wedge of .25 inch thickness are to be applied. 
286. Determine the mean thickness of a tooth. 
287%. With reference to Fig. 27 of the Instruction Book, calculate 
the approximate effective teeth section belonging to a pole. 
288. Assuming, as already mentioned, an average pole arc ratio of 
_ = .60, and that about 10% of the total armature length 
is taken up by paper insulation, calculate the resulting 
armature length. 
289. The armature iron length, including 10% for paper insulation, 
being definitely fixed to 9.5 inches, state the overall length 
of same, making provision also for two ventilation ducts, 
each of .5 inch width. 
290. With reference to Fig. 26 of the Instruction Book, determine 
the necessary effective section of the armature core and its 
height above the slot. 
291. The pole core length being fixed at 9.5 inches and assuming & 
pole core density of 95,000 lines per square inch and an ay- 
erage leakage factor of o 1.20, calculate the effective 
é 
