| 摘要 |
PURPOSE:To control a speed without tripping an overcurrent of an induction motor (DM) during its reverse rotation by detecting a rotating speed and a rotating direction from a residual voltage of the motor. CONSTITUTION:When an induction motor (DM) 2 starts to rotate, a rotating speed detector 4 calculates the rotating speed of the DM 2 according to a residual voltage detected by a residual voltage detecting transformer 3, and a rotating direction detector 18 detects a rotating speed of the DM 2. If the DM 2 now makes a reverse rotation, an inverter 1 outputs a frequency to meet the speed of the DM 2. A phase sequence of the output frequency at that time is reverse, the output voltage is initially '0' and gradually increased to a voltage to meet the output frequency. And, the speed is decelerated to '0', and then accelerated to a command value based on a command signal of a necessary speed. Then, if the DM 2 makes a normal rotation, the phase sequence of the output frequency is positive, the output voltage is initially '0', and gradually increased to a voltage to meet the output frequency. It is accelerated or decelerated to the command value based on the command signal of the necessary speed. |
