Publication: Design a large capacity variable voltage of dc power supply
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Date
2010-04-01
Authors
Ibrahim, Amin Shaharuddin
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Abstract
In this project, a large capacity variable voltage of DC power supply will be designed and constructed. The main function in this project is to convert single phase AC signal to DC signal. The output DC voltage is variable when the firing angle of thyristors is changed. Resistor and highly inductive load are used as load of converter in this project because the load current of converter cannot reach zero and it flow continuously without ripple. The converter has been divided into two main parts. There are switching circuit and single phase full wave converter. The switching circuit is implemented by using a phase control IC, SIEMENS TCA 785. The main reason that this IC being suggested in this project is that it provides two outputs Q1 and Q2 that can be used to trigger a pair of thyristors simultaneously. The switching circuit hardware implement produce firing angle from 0° to 180°. Amplifier circuit is used to amplify 25mA from output of IC TCA 785 to 210mA in order to trigger large thyristor which has minimum gate current of 150mA. The single phase full wave converter is built using four thyristor and input voltage is 240AC. From simulation result, average DC voltage of the single phase full wave converter varied from the 0V to 216.08V. The maximum power can supply by this converter is 4.68kW. In this project, the firing angle of DC converter is limited until because only in this range converter acts as DC converter and for firing angle , it acts as inverter.