| 摘要 |
PURPOSE:To detect the operational incapability of an automatic control system due to voltage drop of its power source, by detecting abnormality in such a way that optional two pairs of the three lines of a threephase-power source are rectified through transformers, respectively, and the AND of the two outputs is taken by comparing the rectified voltages with a reference voltage. CONSTITUTION:The voltage across the power supplying lines (b) and (c) of the three-phase power source is rectified by means of a rectifier circuit 8 through a transformer 3 and inputted in a comparator 11 where the rectified voltage is compared with the voltage of a reference voltage setting device 16 (for example: 180V at three-phase 200V). When the rectified voltage is >=180V which is normal, '1' is outputted and, when abnormal, '0' is outputted. Regarding the voltage across the power supply lines (a) and (b), a simular output is obtained and both the outputs are inputted in an AND gate. When both the outputs are '1', the operation-able information of an automatic control system is informed by turning on a transistor 14 and pilot lamp 15. In addition, when the fuse of any one of the power supplying lines (a), (b) and (c) blows out, abnormality display is made.
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