ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 
75. 
76. 
3%. 
78. 
79. 
State the formula which gives the bearing friction losses in 
watts of an alternator. 
What are the bearing friction losses of a 770 KVA. alternator 
running at 214 r. p. m. having a shaft diameter inside the 
bearings of d = 9 inches, and an effective bearing length 
of 1 = 20 inches? 
State the different items of iron loss in an alternator. — i 
Give the limits of the magnetic armature core densities for a 
frequency of from 25 to 120, in the form of two curves. 
In what approximate proportions are the magnetic densities 
distributed in the armature core and teeth? 
What average amount of losses per pound of effective arma- 
ture iron is to be anticipated in a commercial alternator? 
Give the approximate iron loss of a 250 KVA. alternator, and 
state the amount of iron losses per pound, using the respee- 
tive curves of Figs. 14 and 28 of the Instruction Paper. — 
In the case of a 400 KVA. alternator for a frequeney of 50, 
it has been calculated that the amount of teeth iron should ~ 
be 580 pounds for a saturation of 84,000 lines per square’ 
inch; the amount of armature iron, 4,200 pounds for a 
saturation of 30,000 lines per square inch; and that the 
laminations should have a thickness of 0.2 inch. Find 
the total amount of armature iron losses in this alternator. 
What extra factor may considerably affect the resulting eddy 
current losses? | 
Give the usual armature copper losses of a 600 KVA. alterna- 
tor. | 
What usual current densities are employed in the armature 
conductors of an alternator? 
Give the formula for determining the power lost in the arma- 
ture winding of an alternator. 
Give the formula for determining the ohmie resistance of the 
armature winding of an alternator. 
