| 摘要 |
PURPOSE:To prevent an overvoltage current from lowing to an auxiliary power supply even though a voltage detector for detecting an auxiliary power supply voltage at higher side fails in a high voltage section. CONSTITUTION:For a first and a second contactors 8 and 9 provided for a first and a second auxiliary power supply lines 6 and 7 connected to a tertiary winding 5 of a transformer 4 for transforming power from an AC stringing 1, the voltage of the first and second auxiliary power supply lines is detected by a first and a second voltage detectors 10 and 11, the first contactor is closed when the voltage of the first auxiliary power supply line is almost equal to the rated output voltage, then the second contactor is opened, and the first contactor is opened when the voltage of the second auxiliary power supply line is almost equal to the rated output voltage. Moreover, transfer switching control is performed for closing the second contactor. And a protecting operation for opening both the first and second contactors are opened together when an overvoltage higher than the rated voltage of the second auxiliary power supply line is detected by the protecting voltage detector 14 in the high AC stringing voltage section. |
