166 ARMATURE CONSTRUCTION 



same direction around the circuit. This has been done in Fig. 197, 

 where it will be seen that the arrow-heads all point in the same 

 direction when the winding is traversed from conductor No. 1 to 

 No. 6. 



The ends of conductors 1 and b' are the terminals of the 

 winding, and these we must connect to the machine terminals, 

 or to the collector rings (or slip-rings) which are shown as two 

 thick concentric circles in the centre of the diagram. 



The diagram as it now stands represents a single-phase arma- 

 ture winding having one conductor per pole. 



The external circuit is connected to the machine terminals. 

 So long as the external circuit is not closed there is no completed 

 path for the current from one collector ring to the other, and the 

 circuit of the armature winding is open i.e. it is an " open 

 circuit" winding. 



Now, suppose we have two conductors located under each pole in 

 place of the one per pole in Figs. 196 and 197. These will stand as 

 shown in Fig. 198, where they have been numbered 1, IA, 2, 2A, etc. 



If the direction of the rotation is as indicated, the induced 

 electromotive forces will be in the relative directions shown in 

 each of the conductors. 



Now we will first connect up the conductors at the back end 

 of the armature, that is, the outer end in the diagram, following 

 the convention of Chap. VIII. We may do this in the manner 

 shown in Fig. 199, which gives us a set of six elements, each 

 element consisting of two conductors connected together at the 

 back end of the armature. 



We have now to connect these elements together in such a 

 way that the arrow-heads (representing the direction of the 

 induced electromotive forces) follow each other in the same direc- 

 tion round the circuit. 



The simplest way of doing this and giving a symmetrical 

 arrangement of the connections is in the manner shown in 

 Fig. 200, i.e. by connecting at the front end of the armature, 

 conductors 2 to 3, 4 to 5, and 6 to 1, which leaves us with IA and 

 6A to connect to the terminals. These are connected each to a 

 collector ring or stator terminal, as shown; and if the circuit be 

 traced continuously, starting at one ring and terminating at the 

 other, it will be seen that all the arrow-heads point in the same 

 direction along the circuit, i.e. the electromotive forces in all the 

 conductors act at any one instant in the same direction, and, 

 consequently, are added to each other. 



