| 摘要 |
PURPOSE:To stabilize a load drive without reducing the capacity of a motor by switching a power source to the motor in response to the variation in the frequency. CONSTITUTION:A variable frequency power converter 14 is provided between a commercial power source and an AC motor 12, which are connected via a switch 16, and a bypass circuit 20 having a switch 18 is provided for the converter 14. The switches 14, 18 are switched by a switch controller 22 to connect the motor 12 to the commercial power source 10 in the rated frequency range of the motor, and to connect the motor 12 to the converter 14 in the range of the frequency lower than the prescribed value. Thus, the phase difference between the voltage of the motor and the voltage at the power source can be eliminated at the switching time. |
