| 摘要 |
PURPOSE:To prevent the reduction of a torque of a motor even when a current is limited at an overload time by providing a circuit for detecting the peak value of the current, thereby repeating ON and OFF of an inverter. CONSTITUTION:When an overload is applied to a motor 3 and a peak value detector 16 produces an H output, an inverter is turned OFF via NAND gates 101-103, and the positive voltage of a comparator 18 is inputted to an integrator 7 via a switch circuit 19, thereby decreasing a V/F command. If the output current abruptly decreases when the inverter becomes OFF, the inverter is turned ON via the gates 101-103. This operation is repeated to lower the inverter frequency and the converter output voltage, thereby preventing a motor torque from decreasing. |
