| 摘要 |
PURPOSE:To avoid the malfunction of a switch when judging if a over-current relay is or not, by providing an function discrimination means in which the overcurrent is judged to exist when it is discriminated that no trip coil is detected and on the other hand, the function is judged abnormal when it is discriminated that an overcurrent detection relay is ON. CONSTITUTION:With an overcurrent detection relay 18 ON, if no trip coil 23 is connected to a voltage circuit 19, it is determined that the overcurrent is detected, and if the trip coil 23 is connected, it is determined that the action is abnormal. In the former case, the overcurrent is detected in a three-phase bus 2, the contact of a relay X is switched from (b) to (a) and a trip coil circuit 19 is opened. As it gets in an SO function, the overcurrent detection relay 18 is OFF, a trip relay contact 22 is ON if service interruption is ascertained, and the driving current is caused to flow to the trip coil 23 to interrupt the switch. In the latter case, as no overcurrent is detected, no contact of the relay X will act and the trip coil 23 remains connected to the voltage circuit 19, so that it is determined that the action is abnormal. |
