THE INDUCTION MOTOR. 



395 



and synchronism. By suitably choosing the successive 

 steps of the starting resistance, and moving the starter 

 handle over at the correct rate, as the motor increases its 

 speed it is possible to insure that the motor is started 

 and got up to speed under the most favourable conditions, 

 that is, under conditions at which it can exert the 

 maximum torque. 



When the starting torque is plotted as a function 

 of the rotor resistance, as has been done for a different 



110 



FIG. 191. RELATION BETWEEN STARTING CURRENT AND TORQUE AND ROTOR 

 RESISTANCE. 



machine in Fig. 191, the value of the resistance giving a 

 maximum starting torque is seen at once, being the 

 resistance corresponding to the peak of the curve. This 

 would correspond to the value of the resistance giving 

 the curve of '18 ohm in Fig. 190. The points to the right 

 of this are lower, because the maximum turning effort is 

 only reached with a slip, greater than 100 per cent., as 

 explained above. Points on the curve to the left of the 

 peak indicate values of the resistance, for which maximum 



