22 SYNCHRONOUS MOTORS 



The power supplied by the generator to the motor will be 

 P 1 =E l IcosOAD 



'DAXCA 



2 R 

 In like manner, the electric power consumed by the motor will be 



JDCXCA 



2R 



The power lost by ohmic resistance (Joule effect) is equal to the 

 difference, or to 



CAXCA 



2R 



The diagram therefore determines, by the measurement of simple 

 lines or areas, the current strength and the power of each of the 

 two machines, for each value of the phase-angle. 



Let us suppose that the vector OA (Fig. 13) is stationary, and that 



the phase-angle, 0, varies. The point B' will describe a circle of radius 

 OB'\ the point D describes a circle constructed on OA as a diameter; 

 finally, it is easily seen that the point C describes a third circle having 

 for its center and for its radius the projections of O and of OG on a 

 right line, A F, making the angle 7- with OA . These three circles hav- 

 ing been drawn, the conditions of operation can be followed on the 

 diagram. Mr. Blakesley has thus determined the limits of stability 

 and the maximum electrical efficiency. 



