| 摘要 |
PURPOSE:To minimize the remaining resistance value of a liquid resistor by stopping an electrode lowering operation after it is contacted with the lowest electrode stopper. CONSTITUTION:When a main switch 2 of a main motor 1 is closed, an auxiliary contact 2-a will close, thereby causing a contactor 5F to be energized and allowing the control motor 4 of a liquid resistor 1 to carry out an electrode lowering operation. On the other hand, a timer 10 for closing the auxiliary contact 2-a is energized to close the contact 10-a after the period of time for producing the rush current of the motor 4. When the resistor 1 performs the electrode lowering operation and is thus contacted with the stopper at the lowest electrode position, the motor 4 is locked, thereby increasing the primary current of the motor 4. An overcurrent relay 9 detects this increased primary current, allowing a relay contact 9-a to be closed, thereby energizing the self-holding auxiliary relay 11 and opening the contact 11-b to demagnetize the coil 5F of the contactor, and the electrode lowering operation can be stopped. |
