ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 17 
15%. 
158. 
1 59. 
160. 
161. 
What special care is to be taken in determining the slot 
dimensions of an: alternator? 
State the principal disadvantage of high pole cores. 
What is the maximum allowable winding depth of the field 
coils ? 
What should be the average specific cooling surface of the 
armature per watt loss? 
Mention the different parts of the armature of an alternator 
which provide cooling surface. 
State the formula for determining the temperature rise of 
the armature. 
What should be the average specific cooling surface of the 
magnet wheel per watt excitation loss? 
State the formula for determining the temperature rise of 
the magnet wheel. 
The normal excitation current of a 12-pole alternator is 
244.5 amperes. The field coils have a total resistance of 
.0865 ohm. The external cylinder surface and the two 
sectional areas of one pole core, which earries a coil 
consisting of flat edge wound copper strips, offer a cooling 
surface of 350 square inches. The peripheral speed of 
this alternator is 7,150 feet per minute. Calculate the 
temperature rise of the magnet wheel of this alternator. 
What average amount of field ampere turns should be 
allowed for the air gap? | 
What condition does the application of a small air gap 
affect ? 
What condition speaks in favor of large air gaps? 
Follow the design of the 400 KVA. three phase alternator 
for which the necessary data is given in Pars. 210 to 268, 
step by step, and state the principal formule which have 
been applied in calculating the respective values. 
