| 摘要 |
PURPOSE:To switch a commercial power source and the titled device, by providing a number of rotation detecting device in the induction motor, detecting the fact that the deviation between the number of rotation and the output frequency of a converter becomes a value lower than a specified value, and switching the motor to power converter driving. CONSTITUTION:The induction motor 31 is connected to the output of the power converter device 2 through a contactor SW12. Meanwhile, the motor is connected to the commercial power source 1 through a contactor SW11 together with the input of the device 2. When the SW11 is opened and the commercial power source is cut off, the output of the number of rotation detector 41 for the motor 31, whose speed is naturally reduced, is sent to a slip detecting device 61 together with the output frequency signal from the device 2. Said detecting device 61 detects the fact that the difference between both signals becomes the value lower than a slipping value for suppressing the current value within a specified value. An AND value of this result and a turn ON condition 51 of the contactor SW12, which is formed based on the state signal of the contactor SW11, is obtained by a logic circuit 71. The contactor SW12 is turned ON by the output signal, and the induction motor 31 is switched to the power converter driving. |
