58 



SYNCHRONOUS MOTORS 



which is the corresponding V-curve (Fig. 32). These curves show 

 clearly that the V becomes more rounded as the corresponding power 

 PZ increases. This fact is, moreover, verified by experience, as shown, 



ec 



so 



/7 



FIG. 32. 



for example, by the curve in Fig. 33, obtained experimentally from a 

 synchronous motor of Labour type running at constant load of 5 k.w. 

 (half load). 



)Lciting Current, Amperes 



FIG. 33. 



The sharpest V is obtained with no load. Theoretically, the curve 

 ^2=0 (Fig. 32) ought to present an angular point at the axis of amperes; 

 but, in practice, the power consumed by friction, eddy currents 

 etc., when running without load, is not negligible, and, for these rea- 



