| 摘要 |
PROBLEM TO BE SOLVED: To increase torque at the time of low speed by bringing the q-axis current command value to zero, when the absolute value of a speed command value or a speed estimated value is lower than a set value and employing a value obtained using a frequency estimated, based on the difference between the speed command value and the speed estimated value as a frequency command value. SOLUTION: A speed controller 5 receives a difference signal between a signal ωr * and a speed command signal ωr * from an adder 21, an output signal Ga2 from a function unit 113 and a slip frequency estimation signal ωs ** and produces a q-axis current command signal Iq*. The slip frequency estimation signal ωs ** is determined by a slip frequency estimator 9, based on the signals ωr *, ωr * obtained from the adder 21. Since the speed controller 5 outputs O as the q-axis current command signal Iq* in a low-speed region, the q-axis current is controlled to O, and the speed command estimation signal ωr * is no longer is susceptible to the cause of estimation error, i.e., the resistance setting error. |
