362 



ELECTRICAL EQUIPMENT 



normal supply of exciting current, and the method employed for 

 controlling the field excitation. Where the exciting current for 

 all of the machines is taken from a common exciter bus, the bat- 

 tery would ordinarily be floated directly across this bus, provided 

 its voltage is substantially constant. If the exciter bus voltage 



Voltmeter Connections 

 Pt. No. 1 Charge "A" 

 Pt. No. 2 " "B" 

 Pt. No. 3 Total Batterj 

 Pt. No. 4 Bus 



FIG. 217. Diagram of Connections for Exciter Battery for Emergency Service. 

 Normally off Line. 



is varied from time to time by manual control, the battery can 

 still be kept constantly connected to the bus, but the number of 

 cells in circuit must be adjusted by means of an end cell switch 

 whenever the exciter bus voltage is changed. 



If the exciter bus voltage is constantly varied automatically, 



