SIMULATION AND PERFORMANCE INVESTIGATION OF A HIGH POWER FACTOR CONVERTER FED DC MOTOR DRIVE

Abstract

The conventional ac to dc power-converters are extensively used for the speed control of dc drives because they need no special means for commutation and, the operation is stable. To obtain controlled output voltages, phase-controlled thyristors are used instead of diodes. The output voltage of thyristor-rectifiers is varied by controlling the firing delay angle of thyristors. A semi-converter is a one-quadrant converter and has one polarity of the output voltage and current. A full-converter is a two-quadrant' converter and the polarity of it's output voltage can be either positive or negative with only one direction of output current. Dual-converter can operate in four quadrants and both the output voltage and current can be either positive or negative, thus, permitting four modes of operations as forward powering, forward braking (regeneration), reverse powering and reverse braking (regeneration). The basic characteristics of a phase- controlled converter are that the load voltage and line current waves, are rich in harmonics, and the fundamental current lags the voltage waveform. Hence the use of such converters results in power-quality deterioration 'due to low power factor at increasing firing angles (reduced output voltages), increase in harmonic content of the line current and voltage fluctuations. The non- ideal