192 



ELECTRICAL ENGINEERING 



The compounding of a machine can be varied by connecting a 

 resistance in shunt to the series winding as shown at S in Figs. 

 156 and 157. 



fl ) Shunt Excited 



(2) Separately Excited 



( 3 \ Flat Compounded 



( 4 ) Over Compounded 



HLoad HLoad 3 4Load Full Load l^Load 

 Amperes Load Current I 



FIG. 155. Voltage characteristics. 



In a generator supplying a rapidly fluctuating load the shunt 

 to the series winding must be designed with its inductance in the 

 same ratio to the inductance of the series winding as its resistance 



FIG. 156. Compound gen- 

 erator (short shunt). 



FIG. 157. Compound generator 

 (long shunt). 



is to the resistance of the series winding in order that the variable 

 current may divide up in the correct proportions to give the re- 

 quired compounding. 



