ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 29... 
polyphase alternator, of the revolving field type, to deliver 
current at a periodicity of 50 cycles per second, when run- 
ning at a speed of 250 r. p. m. 
Solution —The designer before entering into the design, 
will proceed as follows to obtain from the curves given in 
e 
—_ 
Es 
i 
TRMCES LW SHTLLINOS 
INQ 
7 
i 
é an 
ane 4m 
— 
S000 L Lat So 
fi: Af 1 — 
2000 ra rae. 
f~00 a 
¢ 700 200 SOO Zoo Yo. 0 B00 Yooco 
OWTPUT IN kia 
Fie 15.—AVERAGE MATERIAL PRICES OF STANDARD MEDIUM 
SPEED, 50 CycLE, PoLyPHASE ALTERNATORS. 
Figs. 14, 15 and 16, the weights, approximate prices of ma- 
terial and labor costs for such a machine. 
From Fig. 14, it will be seen that the total weight of copper 
in the armature and field windings will amount to about 
2,800 l|bs.; the weight of the sheet iron in the armature 
core equals 9,200 Ibs.; and the castings with auxiliaries 
