i68 



ELEMENTS OF ELECTRICAL ENGINEERING. 



values of B for loads of zero, 100 kilowatts and 200 kilowatts respectively. These 

 curves are called the excitation characteristics of the motor. Fig. 143 is based on 

 the values A = I, 100 volts, R=i ohm and X = 0.58 ohm. For the greatest pos- 



I2oo 



lloo 



lOoo 



Qoo 

 800 

 7oo 



600 

 5oo 



+00 

 300 

 *00 



loo 



JOOK.V/ 



2.00 KAV 



)2.7 KA 



AMPERES 



/oo 00 Joo +00 



o 600 Too 

 Fig. 143. 



800 900 JOOO ilQQ /2<H> 



sible intake, 302.7 kilowatts, the characteristic reduces to the point enclosed in the 

 small circle. It was pointed out in Art. 71 that with given load there are two values 

 of / for each value of B, and that the larger value of / corresponds to unstable 



and the smaller value to stable running. The dotted portions of the curves, Fig. 143, 

 correspond to the larger values of /. These dotted portion? cannot, of course, be 

 determined by experiment, on account of the instability of running. 



