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= Example 2. A two pole induction motor designed for operation from a three-phase 415 V (rms) 50 Hz supply has the following parameters at rated frequency: X, = 0.75 ; R, is assumed to be negligible; X = 0.72; R = 0.07 2; and Lm is assumed to be large. The motor is to be operated at variable speed from a three-phase inverter which operates in open loop with constant voltage to frequency ratio (Vs/fs = constant). Perform the following: a) Calculate the motor torque and current when operating at a slip of 0.2 and with a supply frequency half of the rated value. b) If the supply frequency is rapidly increased to the rated value, calculate the values of motor torque and current immediately after the step change in frequency. c) Comment on the behavior of the motor in question (b), and how can be improved.