| 摘要 |
PURPOSE:To eliminate the increase in the capacity of an inverter by increasing the torque of an AC motor at the start for controlling the speed by converting the frequency via an inverter by reducing the voltage applied to the coil of the motor. CONSTITUTION:The voltage of a power source bus B is dropped by an input transformer T1, applied to an inverter THY to convert the frequency, the output is raised through an output transformer T2, then applied to a high voltage AC motor M, thereby controlling the speed. At this time a tap having a transformation ratio less than 1 is provided at the transformer T2, or the coil of the motor M is provided with a plurality of parallel coils to lower the voltage applied to the motor M, thereby increasing the torque in starting. Then, the motor is operated in a normal connection. Accordingly, the selection of the inverter for more than the capacity necessary for normal operation only for starting the motor can be avoided, thereby providing an economic structure. |
