| 摘要 |
PURPOSE:To smoothly operate a load by limiting a load current due to the variation in the mechanical load suspended to the load such as an induction motor or the like or the variation in an AC supply power source voltage at the time of starting or accelerating the load such as induction motor. CONSTITUTION:When a current of a load 10 such as an induction motor or the like is increased at the time of starting or accelerating the load 10, an input current of an inverter 9 increases. A voltage drop is produced as an input of a differentiating circuit 12 by a current detector 11 as a result that the voltage drop across the detector 11 increases, and the input level of an arithmetic amplifier 13 will increase. As a result, the output level of the amplifier 13 is lowered, thereby lowering the input voltage of a voltage frequency converter 5, the frequency output of the converter 5 directs toward downward direction and hence toward low frequency direction, the frequency of an inverter input signal generator 6 is decreased, the frequency of the inverer 9 is decreased, and the rotating speed of the load 10 such as an induction motor or the like is limited. |
