Zigzag Connected Autotransformer Based Controlled AC-DC Converter for Pulse Multiplication

This paper deals with the analysis and design of a non-isolated 36-pulse controlled AC-DC converter for medium power rating drives, field winding supply of large alternators, magnet power supplies, etc. It consists of pulse multiplication in non-isolated 12-pulse AC-DC converter to get 36-pulse converter characteristics without employing zero-sequence blocking transformer (ZSBT). The proposed converter employs a zigzag connected autotransformer, which results in near equal leakage reactance in series with each thyristor bridge. The volt-ampere rating of the autotransformer is small and the converter meets IEEE-519 standard power-quality requirements over wide range of firing angle.