| 摘要 |
PURPOSE:To accurately detect a reverse voltage period with a simple circuit arrangement by detecting the reverse voltage period on the basis of a gate logic signal of an inverter and a reverse voltage detection signal. CONSTITUTION:This detector has a gate logic circuit 9 for obtaining the gate signals of thyristor group forming an inverter, a reverse voltage detector 10 for detecting the reverse voltage applied to the thyristor, a differentiating circuit 11 for defferentiating the rise of the gate logic signal, and a differentiating circuit 13 for differentiating the fall of the reverse voltage detection signal. The logic product of the output of a flip-flop 14 set by the output of the circuit 11 and reset by the output of the circuit 13 and the reverse voltage detection signal is produced to detect the period of the reverse voltage applied to the thyristor. In this manner, even when the commutation superposition angle at the heavy load time and further the reverse voltage wave form is largely deformed by the resonance phenomenon on the circuit, the reverse voltage period can be accurately detected. |
