| 摘要 |
PURPOSE:To facilitate the synchronizating pull-in of a motor by connecting an inverter operating at an arbitrary frequency directly to a motor of operating state and judging whether the motor is power driving time or regenerating time, thereby controlling the inverter. CONSTITUTION:When the power of a motor 8 is switched from a commercial power source to an inverter side, the inverter is first operated at an arbitrary frequency. Then, an electromagnetic contactor 9 is closed, a contact E is closed, and the AC input current value of the inverter is maintained at the command value of no load exciting current. A voltage detecting and discriminating circuit 4 discriminates the voltage polarity of the middle circuit of the inverter, thereby closing the contact A or B. A comparator 11 applied a signal of obtaining from a voltage set signal and a bias signal to a frequency controller 14 through a time function generator 13. When the voltage of the middle circuit becomes zero, the contacts A, B are opened, and contacts C, D are opened, and a contact D is closed. |
