Microcomputer-based single-phase to three-phase cycloconverter

A microprocessor application for a single-phase to three-phase cycloconverter is presented. An algorithm is formulated for the cosine-wave modulation method so that it requires only one reference wave (RW) to generate the trigger pulses for all three phases. The method is implemented on an 8085 microprocessor system with output frequencies that are integer submultiples of the input frequency. The operating principle of the cycloconverter is reviewed. A complete software design of the scheme is given, and test results are presented for an induction motor load. The difference between the experimental and the calculated values of the firing angle is in the range of 0 to 0.51° for the selected step size of 1°. This can be reduced further by reducing the step size from 1° to some lower value. Output voltage and current waveforms for an induction motor load approach sinusoidal