316 



ALTERNATING CURRENTS 



adding or subtracting of individual instrument readings which 

 is necessary when two single wattmeters are used. 



Field Rheostat 



D.C. 



Mains 



D.C. 

 Am. 



Field 

 Terminals 



Load 



rmature 

 Terminals 



FIG. 292. Connections for obtaining V-curves of synchronous motor. 



FIG. 293. V-curves of synchronous motor. 



Figure 293 shows a set of typical V-curves. The curve A B is 

 obtained when the motor is running at very light load. At very 



