182 



ELECTRICAL MACHINERY 



to the first transition connection, these shunts are removed 

 aid not connected again until after point 8 has been reached. 

 At present these shunts are not much used. 



The Railway Controller. A typical railway controller 

 is shown in Fig. 110, and in Fig. Ill is given an enlarged 

 view showing some of the contact fingers bearing on the 



^Resistance Points 1, 2 & 3 

 .Running Point 4 



M/VWVW/- 

 Bridge 



^A^M/vw\A/- 



T 



G \/WWVWW 1ftft5\yO' 



7 wwwwv 'OTVO' G 



> Transition Ppinta 



Resistance Points 5 , 6 & T 



Running Point 8 



FIG. 109. Connections for Bridge Control of Railway Motors. 



copper segments which arfc carried on the main cylinder 

 of the controller. As these fingers break contact with the 

 segments, an arc is formed between a finger tip and a 

 segment tip and, if not taken care of, the arcing would 

 soon damage the controller. The controller is so designed 

 that the arc is formed in a magnetic field which tends to 

 lengthen the arc and so makes it rupture as soon as it is 



