CONVERSION OF ALTERNATING CURRENT. 



175 



two-phase converter, has four collector rings connected to four 

 commutator bars 90 apart (on a two-pole machine) and so on. 

 In the case of a multipolar machine the n collector rings of an 

 72-ring converter are connected as follows : Ring No. I is connected 

 to all the commutator 

 bars * which for a given 

 position of the arma- 

 ture lie midway under 

 the north poles of the 

 field magnet. Let / 

 be the distance between 

 adjacent commutator 

 bars of this first set. 

 Then ring No. 2 is con- 

 nected to all commuta- 

 tor bars I /nth of / 

 ahead of the first set ; 

 ring No. 3 is connected 

 to all commutator bars 

 2/flths of / ahead of the first set; and so on. Thus Fig. 148 

 shows a four-pole two-ring converter, each ring being connected 

 to two commutator bars. 



86. The internal actions of a synchronous converter. In its 



relation to the alternating-current supply a synchronous converter 

 is like a synchronous motor, and in its relation to the direct-current 

 receiving circuit a synchronous converter is like a direct- current 

 generator ; but in regard to (a) the actual motor and generator 

 actions in the machine, (fr) the magnetizing action of the armature 

 current, and (c) the heating effect of the armature current, the 

 machine is essentially unlike a synchronous motor and essentially 

 unlike a direct-current generator. 



* This statement applies to that type of armature winding which is called the sim- 

 plex lap winding. In the simplex wave winding each collector ring is connected to 

 but one commutator bar whatever the number of field magnet poles may be. The 

 multiplex winding is not well adapted to the synchronous converter. 



Fig. 148. 



