| 摘要 |
PURPOSE:To protect a machine against damage by a constitution wherein the voltage across a smoothing capacitor is detected and an overvoltage suppressing thyristor is fired when a predetermined comparison voltage is exceeded to consume power stored in the smoothing capacitor through a suppressing resistor whereas a contactor is opened when the detected voltage exceeds the comparison voltage during idling operation. CONSTITUTION:AC power collected by a current collector 1 is fed through a transformer 3 and a contactor 4-1. It is converted into DC power which is further inverted into three-phase AC power for driving an AC motor 13. When the voltage across a smoothing capacitor 11 is higher than the voltage of a first comparator 15-1, an overvoltage suppressing thyristor 10-1 is fired to consume power, stored in the smoothing capacitor 11, through an overvoltage suppressing resistor 9. When the detected voltage exceeds the voltage of a second comparator 15-2 during idling operation, the contactor 4-1 is released to stop the operation of a converter 5 and an inverter 12. Consequently, DC over voltage is prevented from intruding into DC circuit and the smoothing capacitor 11 is protected against overvoltage. |
