392 



THE INDUCTION MOTOR. 



cluced into the rotor circuit virtually doubling its 

 resistance. The effect is seen to be that the inclination 

 of the straight portion of the curve is halved, and at the 

 same time the hyperbolic portion is raised so as to cut 

 the axis at twice the previous height from the horizontal 

 axis. The height above the horizontal axis, at which the 

 hyperbola cuts the vertical axis, represents the starting 

 torque of the motor, since it is the torque of the motor 



25 



20 



10 



10 20 30 40 60 60 70 80 90 100 



Per cent, of full speed. 

 50 100 150 200 250 300 350 



Amperes. 



Fio. 190. CURVES OF TORQUE, SPEED, AND CURRENT WITH VARYING ROTOR 

 RESISTANCE. 



when stationary. The starting torque is, therefore, 

 increased by increasing the rotor resistance up to the 

 point when it is the top part of the torque curve, which 

 cuts the vertical axis. A further increase of rotor resis- 

 tance will only again diminish the torque. 



It is of great importance to remember that the 

 maximum torque of the motor is constant and independent 



