| 摘要 |
PURPOSE:To obtain high torque characteristics in a low-speed region and a stable speed control in a high-speed region by changing a control system according to a rotational speed. CONSTITUTION:When a speed command omega is less than a specified value omegak, a control mode discriminator 12 sets change-over circuits 8, 9 to the A side to form a current feedback loop. A torque current component is computed from a primary current detected by the current feedback loop, and an inverter output frequency command omega and a voltage command are operated on the basis of the torque current component to be used for PWM control operation. Thus, a high torque is generated also in a low-speed region. When the speed command omega is more than the specified value omegak, the switch for the change-over switch circuits 8, 9 is set to B so as to be used for a frequency operator 6 and a voltage command operator 7. The control of inverter output voltage and frequency is an open loop control by the speed command omega only so that a stable high response can be obtained also at a high-speed rotation. |
