THE ALTERNATING CURRENT GENERATOR 265 



Bus Bars 



Lamp 



Lamp 



chronoscope is used it is then " plugged in " and it will 

 rotate, in one direction if the incoming machine is slow 

 and in the opposite direction if it is running too fast. The 

 number of revolutions per second gives the difference in 

 frequency between the incoming machine and the line. 

 In case lamps are used they will 

 flicker, being alternately bright 

 and dark; the number of flickers 

 per second gives the difference in 

 frequency of the incoming machine 

 and line. 



"Dark" and "Bright" Connec- 

 tions of Lamps. If the lamps are 

 connected straight across the switch 

 blades (as shown by the full lines 

 in Fig. 160), the proper time for 

 closing the synchronizing switch is 

 in the middle of a dark period, 

 while if they are connected zig- 

 zag across the switch (as in the 

 dotted lines of Fig. 160), the proper 



time for closing the synchronizing switcn is at the center 

 of a bright period. 



Cause of Lamps Flickering. The reason for the flicker- 

 ing of the lamps may be seen by reference to Fig. 161. 



Lamp 



Incoming Machine 



FIG. 160. Connection of 

 lamps for Synchroniz- 

 ing; " Dark " Con- 

 nection in Solid Lines, 

 " Bright " Connections 

 in Dotted Lines. 



Lciixip 



FIG. 161. Synchronizing Lamps form Part of a Closed Circuit, Con- 

 taining the Two Armatures in Series. 



Machine A is already supplying load and machine B is to 

 be synchronized with it. The lamps form part of a closed 



