| 摘要 |
PURPOSE:To suppress the large current to a motor at switching and to prevent the cross current from an inverter at the time of the parallel operation by switching the operation to the inverter when the relationship between the output frequency of the inverter and the number of rotation of the motor indicates the zero slip. CONSTITUTION:An induction motor IM is connected to the commercial power source Pc via an electromagnetic contactor 88c. A variable AC power supply IV is composed of a converter portion and a voltage-type inverter portion. The output side of the variable AC power supply IV is connected to the induction motor IM via an electromagnetic contactor 88I. A pulse pickup PP which is a speed sensor senses the number of rotation of the induction motor IM. For switching the operation from the commercial power source to the inverter IV, the frequency is followed to the number of rotation of the motor IM after the release of the commercial power source, and the inverter IV is turned on when the output voltage of the inverter IV becomes sufficiently low, thereafter the switching to the operation of the inverter IV at the specified value is accomplished. |
