| 摘要 |
PURPOSE:To reliably protect the overvoltage of a thyristor which forms an inverter by lowering the output voltage of the inverter before the overvoltage is generated when the current is intermittently continued. CONSTITUTION:The input current of a rectifier 2 is detected by a current transformer 9, full-wave rectified by a rectifier 15 and inputted to a comparator 24. When the input current of the rectifier 2 is intermittently continued, the output terminal of the comparator 24 is fallen to the negative voltage to conduct a transistor 25. A voltage added with +15V is applied to the output voltage of a comparator 20 is applied to the input terminal of a rectifier phase control circuit 21 due to the conduction of the transistor 25, the firing phase of the rectifier 2 is altered by the circuit 21, the output voltage of the rectifier 2 is varied from positive to negative voltage, and the output voltage of an inverter 4 is lowered. The output signal of the comparator 24 is inputted to a defect warning circuit 28, which informs a defect. |
