CONTINUOUS-CURRENT WINDINGS 143 



and are also useful for intermediate capacities where the speed is 

 low. They are characterised by having two circuits through 

 the armature from positive to negative brushes, no matter how 

 many poles there are; each of the two circuits carries one- 

 half of the total current. The "lap" (i.e. "multiple-circuit") 

 winding is more suitable for large machines, and is also required 

 in machines of intermediate capacity where the speed is high. 

 It is characterised by having as many circuits through the 

 armature from positive to negative brushes, as the machine 

 has poles, the current, of course, dividing equally amongst all 



FIG. 169. Completed Wave-wound Two-circuit) Armature. 



these parallel circuits. Thus in a 1600-ampere 16-pole machine 



with a multiple-circuit winding, each circuit carries ( = ) 



\ ID / 



100 amperes. 



Thus, instead of comparing, as in a preceding paragraph, 

 two armatures with the same number of conductors connected 

 respectively as two-circuit and as multiple-circuit windings, we 

 may also instructively compare two armatures for the same 

 current and voltage, but wound respectively With these two 

 types of winding. If the machine has four poles, then such a 

 comparative study will show that the two-circuit winding has 

 half as many conductors, and that each conductor is of twice 

 the section, since it must carry half the total current ; whereas 



