THE ALTERNATOR. 



3 



whose primary coil is in the main circuit, as shown in Fig. 15. 

 This is equivalent in its effect to the insertion of the coil CC di- 

 rectly into the main circuit as shown in Fig. 14. 



Figure 16 shows the actual arrangement of the compound 

 alternator. The small transformer, the collecting rings rr 1 , 

 and the rectifier 5 are all mounted together on the armature 

 shaft. The small transformer is in fact usually wound upon a 

 laminated spoke of the armature core. The alternating current 

 flows through the pri- 

 mary coil of the small 

 transformer before it 

 reaches the collecting 

 ring r. 



The rectifier consists 

 of a commutator having 

 p insulated segments, 

 where p is the number 

 of field magnet poles of 

 the alternator. The odd 

 numbered segments are 

 connected together and 

 to one terminal of the 

 secondary coil of the 

 small transformer, and 

 the even numbered seg- 

 ments are connected 

 together and 'to the other 

 terminal of the second- 

 ary coil of the small transformer. Two brushes, at a distance 

 apart equal to the distance * from center to center of adjacent 

 commutator segments, rub on the commutator and deliver recti- 

 fied current to the series field winding as shown. 



It is necessary to shift the rectifier brushes back and forth until 

 the position is found which gives minimum sparking. Then the 



* Or any odd multiple of this distance. 



