Motor drive system using speed sensorless vector controller

摘要

PROBLEM TO BE SOLVED: To attain stabilized start characteristics by comparing an inner torque command with an outer torque command and employing the larger torque command as an input to a torque controller. SOLUTION: An inner speed controller 116 controls an inner torque command T2 such that a lowest rotational speed command NC' being set by a lowest rotational speed setter 115 follows up an operational speed. If the start of a speed sensorless vector controller 11 is delayed at the time of light load starting and a rotational speed command N is reached with the torque of other motor, the external torque command T1 decreases. Since the output Nc from a speed operating unit 111 is 0, an inner speed controller 116 increases the inner torque command T2 in the positive direction in order to accelerate a motor up to the lowest rotational speed command NC'. Since a priority circuit 117 selects a torque T=T2 , a torque controller 113 is provided with a torque command sufficient for starting the motor. According to the arrangement, stabilized starting characteristics can be attained.