ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 127 
tuick micanite channels. The winding is of the long coil 
type, similar to that shown in Fig. 51. 
The field system has 12 poles, each carrying a coil of 35 
turns, which is built of edge wound flat copper strips, 
having a thickness of 0.125 inch and a width of 1.125 
inches. The turns are insulated from each other by press- 
spahn 0.02 inch in thickness. The material of the arma- 
ture core is soft annealed sheet iron of 0.02 inch and that 
of the magnet pole 0.04 inch thick, while the magnet wheel 
Ba gd 
5S. 
S¥6 
Fie. 66.—400 KVA., 3,500 VoitTs, 500 Revs., 50-CycLE 3-PHASE 
ALTERNATOR, 
rim is of ordinary cast iron. The excitation current is 
supplied by a dynamo with an E.M.F. of 30 volts. 
The machine complies with the requirements of Par. 16, 
regarding temperature rise, and for regulation and effi- 
ciencies see the actual test data given in Fig. 67. 
211. Peripheral Velocity.—The alternator running at a 
speed somewhat above the standard, gives a peripheral 
speed of 7,150 feet per minute measured on the external 
diameter of the magnet wheel. 
The periphery is equal to 54.6 X 3.14— 171.4 inches, and 
