DESIGN, SIMULATION AND HARDWARE REALIZATION OF SINGLE PHASE TO SINGLE PHASE STEP DOWN CYCLOCONVERTER

Abstract

In this project, the design, simulation and hardware realization of a single phase to single phase step down cycloconverter is carried out in detail. The simulation of control and power circuit of cycloconverter is being carried out in Proteus Isis software. A single phase cycloconverter is a direct AC to AC converter for providing variable voltage and variable frequency A.C. Based on input supply; it is either single phase or three phase system which is usually designed for high rating applications such as A.C drives, electric heating etc. A single phase cycloconverter requires four SCRs which are turned ON by the appropriate control signals. It operates as a phase controlled converters. These converters need line or natural commutation which is provided by AC input supply. The thyristors of cycloconverter are switched ON and OFF in proper sequence by using control electronics and gate driver circuits to get a controlled ac output voltage. The function of the control circuit is to generate the trigger pulses in a desired sequence and feed them to the gates of the positive and negative group of thyristors so as to generate a desired output voltage of frequency equal to one fourth of input frequency across a resistive load. The simulation of cycloconverter for firing angle equal to zero and a variable firing angle is being carried out. The systematic generation of the blanking and the gate pulses of switching devices (SCRs) and synchronizing them with the AC input signal is the most important requirement and is performed by means of comparator circuit. In this work, attempt has been made to reduce the switches to reduce the complexity of the control circuit, reduces the switching losses and thereby increasing the efficiency. The total harmonic distortion is measured with and without load. The cycloconverter is designed as a prototype and tested under different operating conditions.