76 ELEMENTS OF ELECTRICAL ENGINEERING. 



compound generator is very nearly independent of the current 

 output as is evident from Fig. 65. 



In practice the voltage of a shunt or compound generator is 

 under the control of an attendant who, by manipulating a shunt 

 field rheostat, may keep the voltage as nearly constant as desired. 



100 



60 



The ordinates of the curve in Fig. 66 represent the voltages of 

 a series generator, and the abscissas represent the corresponding 

 current outputs. The voltage of a series generator increases 

 rapidly with increase of current output as is evident from Fig. 66. 



The dotted portions of the curves in Figs. 64, 65 and 66 show 

 the trend of the characteristic curves for current outputs greater 

 than the normal full load values for which the machines are 

 designed. 



The adaptability of the various types of generator to the re- 

 quirements of the constant current system, or rather the inherent 

 lack of complete adaptability may be made evident by replotting 

 the data on which the characteristic curves of Figs. 64 and 66 

 are based, so as to show the current outputs of the different gen- 

 erators as ordinates, and the resistances of the receiving circuit as 



