Design and analysis of soft start of a three phase induction motor / Ahmad Faiz Ahmad

Nowadays industries are using machinery which has large capacity power rating. The three phase induction motor is commonly used in industries. Large capacity induction motors take very high inrush currents during starting direct from a three phase supply. To avoid this problem, soft start technique during starting is used to get the smooth starting of large capacity induction motors. AC voltage controller topology is used as a means of the soft start technique. By using this starting technique, harmonics rich current will exist particularly during operating at large firing angles. Connecting the active power filter (APF) in parallel with the system will reduce the total harmonics distortion (THD) of the system. This study uses MATLAB/Simulink software to design the circuit. The simulation is using the equivalent circuit of the motor. The parameters of the equivalent circuit referred to the 15 kW (20hp) asynchronous motor types as used in the Simulink library with and without soft start arrangement.