IO 



ELEMENTS OF ELECTRICAL ENGINEERING. 



called a distributed winding. Thus each of the armature wind- 

 ings of the two-phase alternator shown in Fig. 1 1 is distributed 

 in 2p slots, that is in two slots per field pole. 



In the concentrated winding, the electromotive force rises sud- 

 denly in value as the slots come under the pole tips, and falls sud- 

 denly in value as the slots pass out from under the pole pieces, 



Fig. 12. 



whereas in the distributed winding the electromotive force rises 

 and falls more gradually. 



2. Field excitation of the alternator. Usually the field mag- 

 net of an alternator is excited by direct current obtained from a 

 small auxiliary direct-current generator called the exciter. When 



