Publication: Analysis of harmonic current produced by ac-dc converters with various firing angles
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Date
2009-04-01
Authors
Nik Hassan, Nik Mohd Farid
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Abstract
The main propose of this project is to analyze harmonic input current produced by AC to DC converter by varying firing angle.Generally,the analysis of input current can be defined as changes to Total Harmonic Distorted. This overall project analyzes 2 variables to relate firing angle with thyristor by differences of the total harmonic distorted.The AC to DC converter that is used is single phase AC to DC converter and three phases AC to DC converter.The AC to DC one phase converter used 4 thyristor while 3 phase AC to DC converter used 6 thyristor as as switch.The resistance being assumed in this analysis is pure resistance.The values of capacitor and inductor resistance are not considered. The purpose of doing so is to neglect the value of Power Factor for the AC to DC circuit.In this Project,3 steps is taken to analyze the relationship of firing angle in thyristor to the total harmonic distorted.The first step is to use theories of input waveform current harmonic changes and this value is interpreted by Fourier Series.Based on the results obtained from the three methods,for single phase control rectifier,it can is observed that the firing angle is directly proportional to THD,and the range varying angle obeys the standard introduced by IEEE for THD,which is less than 20% for angles of 0° to 40°.For three phase control rectifier,it is observed that the firing angle increases with respect to THD,and no range firing angles obeys the standard of IEEE.This is because based on the experiment,3 phase controlled rectifier,when the varying angle of thyristor is 0°,the THD value is 26.7%,and exceeded the standard fixed by IEEE.