ARM A TURE WINDINGS AND SLOT INSULA TION 91 



conductors moving through the region A. The result will ho 

 a tendency for a current to circulate in the path AECF as 

 indicated by the dotted arrows. The net result will be a strength- 

 ening of the current leaving the machine at one set of brushes 

 and a corresponding weakening of the current at the other set 

 of brushes. This unbalancing of the current may lead to serious 

 sparking troubles. To prevent the inequality of voltage in the 

 different sections of the windings it is necessary to go to the root 

 of the trouble and correct the differences in the reluctance of the 

 various magnetic paths. This cannot, however, always be ac- 

 complished perfectly or in a lasting manner; but, by providing 



FIG. 31. Equalizer connections. 



easy paths for the out-of-balance current components, it is 

 possible to equalize the differences of pressure before the current 

 reaches the brushes. This is done by connecting together points 

 on the armature winding which should be at the same potential. 

 In practice a number of insulated copper rings are provided and 

 connected to equipotential points on the commutator. The 

 dotted lines in Fig. 31 show six equalizing rings. Actually, 

 from six to eight points per pair of poles would probably be cross- 

 connected. 



It should be clearly understood that the equalizing connections 

 of lap-wound armatures do not prevent the unbalancing of 

 currents; but, by providing a short-circuit to the paths through 

 brushes and connecting leads of the same sign, they tend to 

 maintain the equality of currents through the various brush 

 sets. In the simplex wave winding, with only two armature 

 paths in parallel, equalizing connections are not necessary. 



25. Insulation of Armature Windings. No great amount of 

 insulation is necessary on each wire or conductor of an armature 



