CHAP. XII] 



INDUCTANCE OF WINDINGS 



233 



tator be assumed to be stationary, and the brushes revolving in 

 the direction of the horizontal arrow, shown in Fig. 57. Let 

 the machine be provided with a multiple winding (lap winding), 

 so that there are as many armature circuits and sets of brushes 

 as there are poles. The current through each armature branch 

 is, therefore 



....... (155) 



where / is the total armature current and p the number of poles. 



Fio. 57. Part of the armature winding, commutator, and brushes in a 

 direct current machine. 



At each set of brushes two branches of the armature winding 

 are connected in parallel, so that the current th rough 

 of brushes is equal to 2/ t With reference to Fig. f>7. it will 

 be seen that the two armature IT.UK h<-. .V and F, which begin 

 at each set of brushes, may be called, with n-prct to this set, 

 the left-hand branch and the right-hand branch. 



