i-B] COMPOUND GENERATOR. *7 



spending say to normal voltage, and check by the relation 



p=i-i/f. 



These terms are useful because they make possible an exact 

 numerical statement of the degree of saturation of a machine, 

 under working conditions, without the reproduction of a satura- 

 tion curve. For a more complete study, compute p and / for 

 different points and plot. 



PART II. LOAD CHARACTERISTICS. 



ii. The usual load characteristics are the shunt, compound 

 and armature characteristics. 



In taking the shunt and compound characteristics, the machine 

 is left to itself with the field rheostat in one position during the 

 run, the curve showing the variation in terminal voltage with load. 



In taking the armature characteristic the field rheostat is con- 

 stantly adjusted; the curve shows the variation in excitation 

 necessary to maintain a constant terminal voltage at different 

 loads. 



The differential and series characteristics are not commercial 

 characteristics but are included to show more fully the operation 

 of the series winding. (For full-load saturation curve, see 33.) 



12. (b) Shunt Character- 

 istic. This is the working 

 characteristic of the machine 



Q 



when operated at normal | 

 speed as a shunt-wound gen- | 

 erator and shows the varia- 

 tion in terminal voltage with 



, ^ A ~ FIG. 3. Connections for shunt charac- 



load (Curve A, Fig. 4). teristic> 



13. Data. The connec- 

 tions are shown in Fig. 3. Readings are taken of terminal voltage, 

 field current, line current and speed. No speed correction is made, 

 there being none which is simple and accurate. The field rheostat 

 is set in one position and no change is made in it during the run. 

 3 



