Adjustable Speed Drive Control Based on Random Pulse Width Modulation

The Pulse Width Modulation (PWM) power electronics systems often produce objectionable acoustic noise at the PWM switching frequency. For example, in a fan / blower drive, the drive used for the blower should use "spread spectrum PWM" technology (also known as Random PWM) where acoustic noise radiating through the duckwork is a very seriously concerned. This paper shows the theoretical basis for the control strategy and simulation results are presented by the random switching conditions. The system consists of a single- phase induction motor by connecting the main and auxiliary winding of the motor across the bridge as an unbalanced three- phase load and the step-up (boost) converter in order to pop-up the DC bus voltage.