i-B] 



COMPOUND GENERATOR. 



21 



field winding which is in series* with the armature. The same 

 readings of terminal voltage, field current, line current and speed 

 are taken as for the shunt characteristic and no speedf correc- 

 tions are made. 



FIG. 6. Series, shunt, compound and differential characteristics. 



21. In Fig. 6 are plotted shunt, compound and differential 

 characteristics, beginning with the same no-load voltage.^ 



The compound characteristic cannot be made a perfectly 

 straight line from no load to full load. What can be done is 

 to have the terminal voltage at full load the same as the no-load 



* (20a). Short Shunt and Long Shunt. The connection shown in 

 Fig. 5 is short shunt; it would be long shunt if the shunt field were con- 

 nected to the line terminals ac, instead of to the armature terminals ab. 

 Both methods of connection are used commercially, the difference between 

 them being slight. 



t (2ob). A generator is compounded for the particular speed at which 

 it is to operate. When it is to be driven by an induction motor, it may 

 be compounded so as to take into account the slip of the motor, '. e., 

 its slowing down under load. 



$ (2ia). In commercial testing, the compound and shunt characteristics 

 would be taken with the same normal voltage at full load (14). The 

 differential characteristic would not be taken. 



