Abstract—A mathematical model for a three-phase induction motor was developed using d-q axis theory. Investigations were carried out using MATLAB/SIMULINK for steady-state, as well as transient conditions when the motor is supplied from balanced and unbalanced voltage sources. Furthermore, soft and smooth starting of 3-phase induction motor was studied and analyzed through the proper choice of the firing angle (a) of thyristors over the starting period to control the applied voltage. The simulation results were analyzed for three induction motors with different power ratings: 3 hp, 50 hp and 500 hp. The results showed that the soft starting method has the lowest current magnitude, thus eliminating shafttorque pulsations during the starting process and ensuring smooth build-up of torque and speed. It was also shown that increasing the firing angle caused torque and current magnitudes to increase faster, but at the same time it caused the motor to reach the steady-state faster