196 ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 
diameter of the wheel D, will be 22.6 inches, where 
14 1, 
6,200 — Dim 3.14 050 
12 
_ Therefore, the value D, of 22.6 inches will be used in the 
design of this particular machine. 
378. Arrangement of Field System.—The frequency being 
70 eyeles per second and the speed 1,050 revolutions per 
‘ ; 0x 60 
minute, the number of poles will be 2p = i 05 na : I 
3 
In this type of alternator, with the armature in two halves, 
each half will be induced by a magnet wheel consisting of 
4 projections, with a pole are covering the whole pole 
pitch. Under the influence of the central magnetizing 
Fie. 87.—WINDING DIAGRAM OF 55 KVA., StIneLe PHASE 
ALTERNATOR. 
coil, all the projections of one half of the wheel will be 
of the same polarity, and if the left hand poles are north, 
the right hand polar projections will have the opposite 
polarity, namely, south. 
The number of closed magnetie circuits in this case is four. 
379. Arrangement of Armature System.—For each half 
of the armature the slots are 24 in number, but only 16 
of them will receive the winding and the others are left 
empty, see Fig. 87. | 
The pole are ratio being equal to unity and the coil breadth 
ratio to 4, the form factor will be 1.6, as the winding em- 
ployed is of the long coil type. 
The two halves of the armature are to be connected in 
series. 
