234 



ARMATURE CONSTRUCTION 



leaving A and D as terminals, or A and D must be connected 

 together, leaving B and C as terminals. 



The former of these alternatives has been taken in this case, 

 giving the terminals marked S and T. From the winding thus 

 connected up it may readily be seen in what sense it .is retro- 

 gressive : for starting at S and following the circuit, we make a 



FIG. 274. Three-phase, Uni-slot, Symmetrical, Retrogressive Wave Winding. 



complete tour of the armature in one direction to the point B; 

 and then going to point C, we make a complete tour in the reverse 

 direction, arriving at the other terminal, T. 



It is now a simple matter to complete this diagram into a 

 three-phase eight-pole diagram by adding four more conductors 

 (two red and two blue) under each pole; and connecting them up 

 exactly as in Fig. 273. This amounts to superposing on Fig. 273 

 two additional and exactly similar phases, thus giving the dia- 

 gram in Fig. 274. This winding is absolutely symmetrical, having 



