Implementação de ponte conversora modificada CA-CC de oito tiristores para melhoria de fator de potência

Abstract

The purpose of this work is the development and the implementation at laboratory the one full-controlled test bench to operate as a controlled modified bridge and as a conventional bridge and check the power factor improvement the controlled modified bridge in comparison the conventional bridge, considering for both the same average DC output voltage criterion. Also, other experimental results will be evaluated, such as: displacement factor, input voltage and current waveform, output voltage waveform, current harmonic distortion, current harmonic spectrum, auxiliary firing control circuit topology. The main motivations for carrying out this work are: to check experimentally the improvement of the power factor of the modified bridge in comparison to the conventional bridge; to purpose an alternative topology for the auxiliary firing control circuit; to compare the auxiliary firing control circuit to the main firing control circuit. The test bench is an AC-DC converter bridge that works as a rectifier, Graetz configuration, powered by a 4-wire three-phase electrical system. The test bench is equipped with eight thyristors and two independent firing control circuits. The eight thyristors, six are phase thyristors and two are neutral thyristors; the two independent firing circuits, one is a main firing control circuit for phase thyristors, the other is an auxiliary firing control circuit for neutral thyristors. The bench works in two operating modes; in operating mode 1, it works as a modified bridge, in which six phase thyristors, two neutral thyristors, one main firing and one auxiliary firing are working; in operating mode 2, it works as a conventional bridge, in which six phase thyristors and one main firing are working, but the neutral thyristors and auxiliary firing are ineffective.