| 摘要 |
PURPOSE:To enable to effectively convert a variable frequency power source without shock by reexciting before the remaining induced voltage is attenuated in a free running state, thereby effectively detecting the induced voltage. CONSTITUTION:When the terminal voltage of an induction motor 7 which becomes free running state is attenuated and becomes lower than the induced voltage value of sufficient magnitude for normally operating a phase angle detector 9, a timer 22 is operated by the operation of a comparator 20 for 10sec. At this time a switch 23 is opened, a switch 24 is closed, a phase matching control is stopped, and the motor 7 is reexcited by an auxiliary power source 25. In this manner, the induced voltage of the motor 7 becomes large, the phase can be reliably detected. |
