ALTERNATING-CURRENT WINDING 235 



the same number of conductors in each phase. The end connec- 

 tions are thoroughly evenly distributed around the circumference, 

 the only slight irregularities occurring at the points where the 

 terminals are taken out and where the two halves are connected. 



This does not affect the appearance and ^ construction of the 

 winding, as is shown by the Fig. 275, which is a photograph of 

 a wound rotating armature with this type of winding and two 

 conductors per slot. 



An example of a two-phase winding is given in Fig. 276, which 

 relates to an eight-pole stator for an induction motor. There are 



FIG. 275. Three-phase Retrogressive Wave Winding. 



eighty slots and five slots per pole per phase, with four conductors 

 per slot. 



The disadvantageous feature of this type of winding, in common 

 with continuous-current wave windings, is that between the top 

 and bottom conductors in the slots a pressure exists equal to half 

 the full terminal voltage. This necessitates insulating the top 

 conductors from the bottom conductors by an extra strip of insu- 

 lation. The winding is not suitable for high voltages, but for 

 induction motor stators of low voltage, and especially for wound 

 rotors, it is very useful.. 



A further interesting example of the application of the retro- 

 gressive winding is afforded by Fig. 277. This winding is for a 



