Star connected autotransformer based 30-pulse AC-DC converter for power quality improvement in vector controlled induction motor drives

This paper presents the design and analysis of an autotransformer based 30-pulse AC-DC converter feeding vector controlled induction motor drives. The proposed AC-DC converter is based on a star connected autotransformer, designed for producing 15-phase shifted AC voltages for effective harmonic reduction. The proposed 30-pulse AC-DC converter is suitable for retrofit applications, where, presently a six-pulse diode bridge rectifier is being used. The resulting supply current is near sinusoidal in shape with low total harmonic distortion (THD) of supply current and a nearly unity power factor. The effect of load variation on various power quality indices is also presented. The proposed AC-DC converter is found suitable for applications with large load variation and where harmonic reduction is stringent.