ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. FT 
sketch showing the arrangement of the wires. Micanite 
insulation of .07 inch thickness and a fixing wedge of .25 
inch thickness are to be applied. 
220. Determine the mean thickness of a tooth. 
221. With reference to Fig. 27 of the Instruction Book, calculate 
the approximate effective teeth section belonging to a pole. 
w : 
222. Assuming an average pole are ratio of T= .65, and that 
about 10% of the total armature length is taken up by 
paper insulation, caleulate the resulting armature length. 
223. The armature length, including 10% for paper insulation, 
being definitely fixed to 13 inches, state its overall length, 
including 2 ventilation ducts, each of .5 inch width. 
224. With reference to Fig. 26 of the Instruction Book, deter- 
mine the necessary effective section of the armature core 
and its height above the slot. 
225. Assuming a pole core density of 95,000 lines per square inch 
and an average leakage factor of © = 1.2, calculate the 
effective pole core section and the necessary pole width, 
taking into consideration that about 5% of the pole core 
length is taken up by insulation material. 
226. The magnetic density in the cast iron rim should be about 
45,000 lines per square inch; calculate its necessary section 
accordingly. 
22%. Determine the rim dimensions, allowing 1.5 inch projcetion 
on each side of the magnet pole for support and protection 
of the field coils. 
228. By means of Formula 32 of the Instruction Book, ealeulate 
the value of effective back ampere turns. 
229. Caleulate the amount of necessary field ampere turns per 
pole corresponding to the normal open cireuit ‘pressure, 
considering that with regard to the specified voltage drop 
the normal excitation ampere turns must be about 2.25: 
times greater than the normal effective back ampere turns. 
230. The current density in the field winding being: chosen at 
