CURRENT ZERO POINT DETECTION IN NONCIRCULATING CYCLOCONVERTER BASED ON DYNAMIC CHARACTERISTICS OF THYRISTOR-DIODE SERIES CIRCUIT

We have presented a new detection principle of output current zero point in noncirculating cycloconverter(NCC) on the assumption of induction or synchronous machine drives. It is based on difference of reverse recovery characteristics between thyristor and diode in series connection, and zero point is detected by means of reverse voltage impressed at diode terminals. This paper investigates the detection characteristics in more detail. Combinations of thyristor and diode affect the voltage in fairly large degree. When the voltage is impressed, thyristor connected to the diode in series has already been in off state. Snubber circuit removes the restriction imposed on the combinations.