| 摘要 |
PURPOSE:To prevent the damage of a thyristor element by inserting a resistor for increasing a braking coefficient in series with a smoothing condenser at the input side of an inverter, thereby suppressing the discharging current from the smoothing condenser flowing after the inverter is failed in commutation. CONSTITUTION:A braking resistor 13 is inserted to a smoothing condenser 3 which is connected to the series input side of an inverter 4. A current transformer 12 is connected in series with the condenser 3, a current which flows through the condenser 3 is monitored, a signal from the transformer 12 is applied to a current detector 13, and when the discharging current becomes higher than the prescribed value, it is regarded as failure in the commutation, and the gate signal of the inverter 4 is interrupted through a controlling circuit. |
