WINDING OF CONTINUOUS-CURRENT ARMATURES 265 



component coils per slot, as indicated by the three ends projecting 

 from each of the slot portions of the coil, and for this reason it 

 may be designated a " triple coil." 



We have now dealt with the chief methods of constructing 

 forms and coils for continuous-current armatures, and the under- 

 lying principles of these govern the construction of the various 

 other forms and other methods, some of which we shall consider 

 subsequently. 



STRIP-WOUND ARMATURE COILS. 



Most of the previous methods and forms have applied to 

 wire-wound coils. We shall now deal generally with strip- 

 wound coils, and later give a typical example of a case 

 with this type of winding. 



FIG. 310. Jointed Strip Coil. 



FIG. 311. Strip Coil Joint. 



In laying out the windings for a strip-wound barrel type of 

 armature, one of the first questions to be decided is whether we will 

 have soldered or jointless connection between the top and bottom 

 halves of the windings. The arguments in favour of soldered con- 

 nections are that as the defects to which armatures are most liable 

 are those which occur near the surface, sometimes by being damaged 

 in transport, and more frequently by moisture condensation on the 

 surface, such defects are easily remedied by unsoldering the joint 

 at the back loop, and raising the top half of the winding, repairing 

 same, and replacing the bar, the two halves of the coil being as 

 shown in Fig. 310. In high-speed machines, such as turbo- 

 generators and motors, it is quite essential that we have a joint 

 at the back end as indicated in Fig. 311, on account of the better 

 mechanical means of binding the bars in place. The bottom layer 

 of the windings is first put in place, and bands are put over these 

 to hold them fast before the top half of the winding is put in, and 

 then the back loops are soldered. But with moderate-speed 

 machines this is entirely unnecessary ; a jointless winding is 



