| 摘要 |
PROBLEM TO BE SOLVED: To make efficiently executable the sintering of a metal by high frequency large a.c. output by adopting an inexpensive thyristor having no self-arc-extinguishing function for an a.c. switching part and making the thyristor in the a.c. switching part turn on/off to an element on the plus side and an element on the minus side alternately. SOLUTION: By an output current detecting part 4 and a monitoring part 5 monitoring the current between elements, two waiting times are prepd. By this circuit, in the case of output current detection, the output in a holding part 7 holding the output in an input selecting part 6 is fixed, and the timer in the monitoring part 5 is not allowed to count. Moreover, after the release of the output current detection, till the time-up of the monitoring part 5, the driving signal is not allowed to pass. In this way, in the case the OFF-TIME in an a.c. frequency output command part 1 is shortened and in the case the output current flows even at the time of switching in the case the reactance on the output side is large, control is executed in such a manner that, in a d.c. output part 2, outputting does not occur, and the driving signal of the thyristor in the a.c. switching part 3 holds OFF. |
