02-10-2012, 04:58 PM
AC to DC Convert -Operation and Analysis of Three Phase Half Controlled Converter
AC to DC Converters - Three Phase Half Controlled Converter.pdf (Size: 332.96 KB / Downloads: 102)
Introduction
Three phase fully controlled converters are very popular in many industrial applications particularly in situations where power regeneration from the dc side is essential. It can handle reasonably high power and has acceptable input and output harmonic distortion. The configuration also lends itself to easy series and parallel connection for increasing voltage and current rating or improvement in harmonic behavior. However, this versatility of a three phase fully controlled converters are obtained at the cost of increased circuit complexity due to the use of six thyristors and their associated control circuit. This complexity can be considerably reduced in applications where power regeneration is not necessary. In that case three thyristors of the top group or the bottom group of a three phase fully controlled converter can be replaced by three diodes. The resulting converter is called a three phase half controlled converter. Replacing three thyristors by three diodes reduces circuit complexity but at the same time prevents negative voltage appearing at the output at any time. Therefore the converter cannot operate in the inverting mode.