ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 7 
80. 
$1. 
82. 
85. 
84. 
85. 
Give the formula for determining the mean Jength of an 
armature turn. 
A three ; hase alternator designed for 50 amperes at a medium 
voltage has in its star connected armature 216 turns per 
phase. Each conductor consists of two parallel connected 
No. 9 8S. W. G. wires, each wire having a section of .0163 
square inch. The armature core length is 10 inches and 
the pole pitch is 14$ inches. What is (1) the mean length 
of a turn; (2) the total resistance of all three phases; and 
(3) the resulting copper losses for the normal current of 
50 amperes ? ) 
What is the usual amount of excitation losses in a 500 KVA. 
alternator ? 
For what output must the exciter of an alternator be de- 
signed ? 
Give the formula for determining the power utilized in the 
field winding of an alternator. 
The maximum excitation current of a 400 KVA. alternator is 
260 amperes and the resistance of the field coils is .10 ohm. 
What will be the power absorbed in the field winding of 
this alternator? 
Printed in U.S. A, 
