158 



SYNCHRONOUS MOTORS 



the results would be found to differ widely from the curves of Fig. 79, 

 the latter being much more accurate. 



FIG. 78. 



Approximate Diagram 



If the resistance r be neglected in Fig. 76, OC and AC will become 

 vertical and parallel, and the constant-power circles will degenerate 

 into straight lines (see Fig. 81). , 



Following the interpretation of Figs. 27 and (76) we have, as the 

 general interpretation of Fig. 81 : 



10 15 



Field Amperes 



FIG. 79. 



25 



The region to the right of the vertical line 55 corresponds to 

 unstable operation, while the region to the left corresponds to stable 

 operation. 



The region above OD and between LL and SS corresponds to 



