A 3 phase, 60 Hz, 4 pole, 440-v (line-line, rms) induction motor drive has a full-load (rated) speed of 1746 rpm. The rated torque is 40Nm. Keeping the air gap flux-density peak constant at its rated value and (if the load is a centrifugal load that demands a torque, proportional to the speed squared, such that it equals the rated torque of the motor at the rated speed:
1) plot the torque speed characteristics for the following values of the frequency 60, 45, 30, 15 Hz.
2) calculate the speed of operation at the 4 values of the frequency