| 摘要 |
PROBLEM TO BE SOLVED: To prevent generation of torque shortage even in a zero-speed area without being influenced by a speed estimation error, by controlling d-axis current to a normal value or higher and computing a frequency command value based on a speed command value in place of a speed estimation value, if the speed command value is a prescribed value or lower. SOLUTION: To control motor current iq, id according to a q-axis current command value iq* and a d-axis current command id** from a speed controller 5, d-axis and q-axis voltage reference values Vd*, Vq* are computed based on the current command values id**, iq* and a frequency command ω1** in a voltage computing device 13. In a zero-speed area, a torque decrease is apt to occur due to various causes, therefore, a speed command value ωr* is selected to be outputted in place of an ω1* at ordinary time by a switch 9, and Δsd is added to a reference value id* at ordinary time by a q-axis current command device 11 to control the id so as to strengthen it. It is thus possible to prevent generation of torque shortage even in a zero-speed area. |
