86 



ELECTRICAL MACHINERY 



the conductor comprising each path is No. 10 B. & S. wire 

 the safe current capacity per path is between 11.1 amperes 

 and 16.7 amperes say 14 amperes. As there are four 

 paths in parallel on the armature and as each path can safely 

 carry 14 amperes, the armature may safely furnish 56 amperes 

 to the external circuit. If the same sized wire was used for 

 a wave winding, in which there would be only two paths, 

 the safe capacity of the armature would be 28 amperes. 



Formed Coils. So far we have said nothing about the 

 actual process of winding the armature. The older machines 



Brushes 



Commutator 



i r r 



rzi 



FIG. 46. A Developed View of a Wave Winding. 



were all hand-wound but practically all modern machines 

 are wound with formed coils. Suppose that an armature 

 is to be wound with a coil pitch (i.e., back pitch) of 10 slots 

 in a certain armature, and that there are to be six turns 

 per coil. Instead of actually winding six turns of suitably 

 insulated wire in the proper slots (hand winding) the wire 

 may first be wound upon a wooden form, shaped in such a 

 fashion that when the formed coil is taken off this wooden 

 form it is of the right shape and size to be slipped, com- 

 plete, into the prpper slots. 



