Patent ID: 7463005

Claim:
A vector control method for an a.c. motor without using a sensor, the a.c. motor comprising: a power converter for outputting electric power to the a.c. motor; an exciting current command calculating unit for calculating an exciting current command from the magnetic saturation property of the a.c. motor to an arbitrary magnetic flux command; a torque current command calculating unit for calculating a torque current command from an arbitrary torque command and the magnetic flux command; a current detecting unit for detecting current supplied to the a.c. motor; a coordinate transformation unit for transforming the detected current to a stator coordinate system; a vector control and calculating unit for controlling and calculating a vector from the exciting current command, the torque current command, the coordinate transformed current detected value, a speed estimated value and a magnetic flux phase estimated value to output an output voltage command; a switching pattern generating unit for generating a signal for PWM driving the power converter from the output voltage command; and an all-dimensional magnetic flux speed observer for estimating the speed estimated value and the magnetic flux phase estimated value from the output voltage command and the coordinate transformed current detected value, wherein a coefficient of a determinant used in the all-dimensional magnetic flux speed observer is corrected in accordance with the magnetic flux command.