Alternating current energisation induction machine control unit

摘要

PURPOSE:To stop an induction machine without developing further faults, when the induction machine is stopped due to malfunction of a thyristor converter, by determining timing for causing no increase of current flowing through the thyristor converter and firing an electric valve. CONSTITUTION:When converter current flowing through thyristor converters 5a-5c exceeds over and overcurrent set value, a controller 4 provides gate block signals to the thyristor converters 5a-5c and provides an electric valve firing signal S3 simultaneously. An electric valve controller 10 receives the electric valve firing signal S3 and judges an operating converter based on a thyristor converter operation signal S2. When a converter at positive connection side is operating, an output voltage phase signal S1 is monitored and an electric valve firing signal S4 is outputted when the output voltage goes negative. Consequently, converter current flowing through the thyristor converters 5a-5c is brought quickly to zero.