Induction Motors, Part XXII: What is the effect of changing the rotor resistance? 7/1/2014
Channel: Lutfi Al-Sharif
Date: 2014-01-08

This video discusses the effect of changing the rotor resistance of an induction motor on the speed torque curve.  Increasing the resistance increasing the starting torque, but worsens the efficiency at rated load.  Decreasing the resistance of the rotor decreasing the starting torque but improves the efficiency at rated load.  The Wound Rotor Induction Motor makes use of this principle by allowing the user to have large starting resistance (in order to increase the starting torque) and then reducing the rotor resistance once the motor gets up to rated speed in order to improve the efficiency.
The video finishes with an unscheduled discussion on induction generators!!! :-)