| 摘要 |
PURPOSE:To balance the loads between AC motors in the case a plurality of the AC motors are driven in parallel by a variable voltage means and vaiable frequency means, by adjusting the input voltages to the individual variable frequency means and providing the difference in each of supplying voltages. CONSTITUTION:The variable voltage means 8 and the variable frequency means 9 vary the voltage and frequency in proportion to a speed reference 1, supply the AC voltages whose voltages and frequencies are the same to each AC motor 3, and drive each motor in parallel. At this time, if the load characteristics of the AC motors are not aligned, unbalance is generated in the torque. Since the torque of the AC motor is proportional to the square of the terminal voltage, the terminal voltage must be varied for every motor in order to align the load characteristics of the motors. Therefore, series variable resistors 10 are provided in front of the variable frequency means 9, the input voltage of the variable frequency means is adjusted, and the loads are balanced. |
