ALTERNATING: GENERATORS AND SYNCHRONOUS MOTORS. 149 
270. 
271. 
given in Figs. 59 and 60. The normal output of this 
two phase alternator with two independent armature 
phases is 375 KVA., when running at a speed of 933 per 
minute and generating a phase current of 624 amperes at 
50 eycles, with a terminal voltage of 3,000 volts. 
The armature is two phase wound and the winding is placed 
in, 256 slots, each slot containing 15 eonductors, and each 
conductor composed of two parallel connected No. 9 
S.W.G. wires. The coils are placed inside the open slots 
which are insulated by a 3x inch micanite tube. The 
type of winding employed is the one given in Fig. 48. 
The magnet system consists of 64 machine wound coils, the 
size of conductor being No. 1 8.W.G. double cotton cov- 
ered round wire. The number of turns per coil is 80. 
The material of the armature core is 0.02 inch soft annealed 
sheet iron, that of the pole pieces 0.04 inch stampings, 
and the wheel rim is made of ordinary east iron. 
The generator is driven by a direct coupled steam engine 
and has to work in parallel with other machines of 
similar design, while supplying current to a power circuit 
of cos Pp = 0.8. 
Determination of Wheel Diameter.—The wheel 
diameter has been determined with particular regard to 
the provision of the necessary space for the magnet wind- 
ing and the application of the flywheel effect in the magnet 
wheel itself. aa 
Flywheel Effect.—The engine makers specified in this 
particular case a flywheel effect which is equal to W X D? 
= 2,200 tons feet square, where W equals weight of re- 
volving part in tons, and D the diameter in feet. 
This condition is in the present case complied, with, as the 
total weight of the magnet pieces and coils is 3.25 tons, 
and their gyration diameter is 13.5 feet; consequently the 
flywheel effect of this part is equal to 3.25 X 13.57 = 590 
tons feet square. 
