For the motor of Problem 17, compute and plot using EXCEL the rotor current and motor torque from slip s = 1 (starting) to 0.05 (full load) with rotor resistance varying from 0.5 to 2 Ω/phase. Then, in reference to the chart, discuss the starting torque, full load speed, and full load current as the rotor resistance varies over the range. Also discuss what those variations mean in terms of the induction motor design for various starting torque and running efficiency requirements.

Data from problem 17

For a three-phase, 60-Hz induction motor with phase values of stator voltage V = 120 V, R_rotor = 1 Ω, and L_rotor = 1 mH, compute and plot using EXCEL the rotor current and motor torque for slip varying over a wide range of s = −1 to +2 pu, that is, from backward rotating to supersynchronous speed. Then, in reference to the chart, discuss in each speed range the torque, current, and power variations, and what they mean in terms of using the induction machine as a motor, generator, or brake.