Power factor improvement of AC chopper-based induction motor drive

AC chopper or AC voltage regulators have been widely used in induction motor drive systems. These drive systems are normally negatively viewed for their low power factor and their high line current harmonic contents. In this paper, a new asymmetrical pulse-width modulated (APWL) controller for AC choppers is proposed. The proposed scheme is used to drive a three-phase induction motor. The main advantage of the proposed APWM technique is its high power factor. A mathematical model of the drive system is developed. This model is general enough to simulate most of the AC chopper control algorithms as applied to induction motors. The model is used to explore several characteristics of the proposed APWM controller. These characteristics are compared with those of the conventional AC chopper controllers. Digital simulation of the mathematical model confirms the effectiveness of the presented scheme.