| 摘要 |
PURPOSE:To permit the prevention of commutation failures by connecting the series-circuit of a resistor and a voltage regulator diode to a thyristor in anti-parallel wherein both ends of the voltage regulator diode is connected to a comparator to form a reverse voltage detection circuit and controlling is performed based on this circuit. CONSTITUTION:The series circuit of a resistor 15 and a voltage regulator diode 16 is connected across a thyristor 5 to pick up potential alteration across the voltage regulartor diode 16, If a comparator 17 sends an output signal only when the signal level at an input terminal is lower than zero voltage potential, a signal is outputted from the comparator 17 only the duration of reverse bias at the time of thyristor's 5 commutation. With the output 101 in each reverse voltage detection circuit 18 synchronized with the commutating signal of the thyristor corresponding to the output and switched by an analog switch 19, the reverse voltage signal of each thyristor 3-8 will be obtained as a series signal. A commutating signal 103 in a gate controlling circuit 20 is inputted to a timing circuit 21 to generate a switching signal 104. |
