| 摘要 |
PROBLEM TO BE SOLVED: To restrain torque ripples caused by the offset of a current detector, instability of current control caused by various errors, and excessive M-axis current, when a AC motor is torque controlled by a vector control inverter. SOLUTION: An M-axis current command value TMM* is obtained from a new secondary magnetic flux command value ϕ22* obtained by restricting the upper limit of a secondary magnetic flux command value ϕ2* by means of a magnetic flux command upper limit computing unit 62 and a secondary magnetic flux upper limiter 63 to correspond to a rotational speed ωR, and the lower limit of the secondary magnetic flux command value ϕ2* by means of a magnetic flux command lower limit computing device 31 and a secondary magnetic flux lower limiter 32 to correspond to the rotational speed ωR. A T-axis current command value change circuit 22 converts a T-axis current command value IT* to be inputted into a new T-axis current command value ITT* which is inversely proportional to the new secondary magnetic flux command value ϕ22*. Torque ripples can be restrained by keeping the secondary magnetic flux above the lower limit value, even if the motor operates at a low speed, and the instability of control caused by excessive motor counter-electromotive voltage by keeping the secondary magnetic flux below the upper limit value, thereby restraining generation of excessive M-axis currents. |
