ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 
oz. 
State the usual method of winding the field coils of revolving | 
field type alternators. 
What is the usual current density between gun metal slip 
rings and carbon or copper brushes? 
Give the average weights of material used in an 850 KVA., 
medium speed, 50-cyele polyphase alternator. 
What would be the approximate cost of labor for this ma- 
chine in England ? 
‘tate the relation between KW. and KVA. 
What is the rated capacity of an alternator which supplies 
800 KW. to a motor circuit having a power factor of cos P 
s=45 
Give the formula expressing the output of an alternator in 
horsepower when its efficiency and capacity in KW. are 
given. 
A 350 KW. polyphase alternator with an efficiency of 93.5% 
at full load supplies current to motor and lamp circuits, 
with a power factor of cos P= .85. What is the rated ea- 
pacity of this alternator and that of its prime mover? | 
_ What, would be the rated capacity of the prime mover when. 
the same alternator in Question 50 supplies energy to a 
lighting circuit only? ) 
State the formula giving the output of a single phase alterna-. 
tor having (1) an open armature winding and (2) a closed 
armature winding. 
Give the formula determining the output of a two phase al- 
ternator, having (1) an open armature winding of two 
independent phases, and (2) a closed armature winding. 
What will be the current in each phase of an 800 KVA. 4,000 
volt two phase alternator with two independent phases? 
Paureiaeieg the same alternator as in Question 54 with a 
--@losed: armature winding, give the voltage and current 
per phase. | | 
