| 摘要 |
PURPOSE:To protect a thyristor element by judging whether a commutation failure or not according to the value of an AC input current when the DC current of a power rectifier is interrupted at low output time or at the starting time, thereby stopping the rectifier by effectively detecting the commutation failure. CONSTITUTION:When a firing signal is applied to the thyristors 3a, 3d of a power inverter 3 from a gate signal generator to start the inverter 3, a current is supplied to a load 4. When a power rectifier 1 is interrupted at the low output time or at the starting time, this influence is presented even at the AC input side of the rectifier 1. The output signal of a current transformer 10 is converted by an AC/DC converter 11, and compared by the set value of a setter 13. When a commutation failure occurs, a gate signal for stopping the rectifier 1 is fed from a control circuit 15. |
