THE INDUCTION MOTOR. 



387 



the form of a curve. This curve should be compared with 

 the relation between primary and secondary currents 

 actually obtained in the experiment, and plotted as the 

 full line in 'Fig. 184. 



If the uppermost point in the curve in Fig. 189 be 

 taken as the point of normal full load, it will be seen that 

 the no-load current is about one-half of the full-load 

 current. This condition corresponds roughly to the case 

 of small motors. With larger machines the no-load 

 current may be about one-third of the full-load current, 



FIG. 189. CURVE SHOWING RELATION BETWEEN PRIMARY AND SECONDARY 

 CURRENTS. 



and the relation between primary and secondary current 

 is that shown by the lower curve. 



Thus, the no-load current of an induction motor is con- 

 siderably higher than that of a direct-current motor, 

 although the no-load power absorbed is less. From Fig. 

 188 it is easy to see that the phase of the primary current 

 becomes more and more nearly one-quarter period in front 

 of the no-load current, and consequently approaches more 

 nearly the phase of the applied voltage. The power- 

 factor thus increases rapidly with increasing' loads. These 



