THE INDUCTION MOTOR 



343 



added to the rotor circuit, the torque and the power factor 

 increase, while the current decreases. A certain external 

 resistance (in Fig. 223 this is 2.2 ohms) gives a maximum 

 starting torque; if more than this is inserted the torque 

 again falls off. The proper starting resistance for this 

 motor would be about 3 ohms; for this resistance the 

 torque is still fairly high, the power factor is comparatively 

 high, and the current is not much in excess of the full- 

 load current. 



100 



123 ~4 5 



Output in H.P. 



FIG. 224. Running Characteristics of a Small Wound-rotor Induc- 

 tion Motor, Having No External Resistance. 



96. Running Characteristics. The running character- 

 istics of the ordinary small induction motor with a low- 

 resistance rotor are shown by the curves of Fig. 224. The 

 no-load current (called the "running-light" current) is 

 generally between 20 and 40% of the full-load current. 

 The current increases with increase of load, and increases 

 more rapidly for the overloads. 



The speed falls off slightly as the load increases, the 

 decrease from no load to full load being generally less than 



