| 摘要 |
PURPOSE:To control the output frequency to a specified value depending on an electric signal associated with an output voltage signal in determining whether an output voltage is held below a specified level at the time of controlling an open loop current type AC motor. CONSTITUTION:AC power of a 3 phase AC power source 1 is converted into a DC power with a phase controllable rectifier 3 and smoothed with a DC reactor. Then, it is converted into AC power of a variable ferquency with an inverter 5 and fed to an induction motor 6. When the operation is performed, with a selector switch 30 set to the position 1, a speed reference signal 11 is inputted into an input limiting circuit 12b and the output serves as the voltage reference 121 and the frequency reference signal 122. As increase in the lead reaches the limit of current of a current inverter, the motor begins to decelerate causing the output voltage to lower. The output voltage detected by an output voltage detection circuit 22 is inputted into a comparator 35 with a voltage reference signal 121. When the output voltage is below the voltage reference signal 121, it provides a one shot signal to allow a flip-flop 37 to output a deceleration signal 371 whereby a selector switch 30, an analog memory circuit 31, an input limiting circuit 12b and a current limiting circuit 38 are started. |
