| 摘要 |
PURPOSE:To detect the normal phase/reverse phase of an input power source without using an exclusive reverse phase preventing unit by providing reverse phase detecting means in protecting unit operation detecting means. CONSTITUTION:A photocoupler 16 is connected through the contact 10a of a protecting unit A10 between phases R and T. A photocoupler 18 is connected through the contact 11a of a protecting unit B11 between the phases S and T. In case of detecting the reverse phase, the reverse phase is detected according to which of the photocouplers 16, 18 is turned ON preferentially. The judgement of the normal and reverse phases may be of one time as the initialization processing when a power source is turned ON, and if the 3-phase AC power source is judged to be normal phase, the ON/OFF signal of the photocouplers 16, 18 becomes a protecting unit operation detection signal. |
