WINDING OF ALTERNATING-CURRENT ARMATURES 325 



The joints between the bars and connectors may now be made. 

 This may be done in a number of efficient ways : 



If the connectors are of thin strip which is fairly flexible, their 

 ends may be wrapped once round the bar and the joint sweated 

 up. If the bars and connectors are very heavy, the joints are 

 sometimes secured with screws or rivets and afterwards soldered. 

 Fig. 403 gives a number of alternate methods of making a 

 suitable joint. 



The above method requires two joints for every conductor, 

 but the number of joints may be halved by shaping the bar as in 

 Fig. 404, which can still be used with closed or half-closed slots. 



If the slots are wide open, the number of joints may be halved 

 by shaping the bars as in Fig. 405. Another alternative (which 

 has, however, two joints per bar) will be seen in Fig. 270, 

 Chap. IX. Fig. 406 is a photograph showing in detail the 



FIG. 403. Methods of jointing Bars and Connectors. 



terminals of a bar wound alternator of which the winding has 

 already been referred to in Fig. 243. 



D. Retrogressive Wave Windings. An inspection of any of the 

 winding diagrams in this class (see Figs. 273 to 278) will show that 

 so far as the shape and connection of the coils are concerned, they 

 are identical with ordinary wave windings for continuous-current 

 armatures. The top conductors in one slot are connected to the 

 bottom conductors in the next slot displaced from it by the wind- 

 ing pitch, as in a continuous-current armature. With this identity 

 in mind we need only refer back to the winding of continuous- 

 current wave-wound armatures to meet the requirements of 

 the present case. One point that should be noted is that with 

 this type of winding the top and bottom sets of conductors 

 in the slots must be insulated from each other, as high pressures 

 exist between them. For this reason the winding is not favour- 

 able to very high voltages. This winding is equally adaptable to 

 wire or strip windings. 



