Patent ID: 7528568

Claim:
The vector controller for a permanent magnet synchronous motor comprising: an electric power converter for driving the permanent magnet synchronous motor; a vector control calculating unit which calculates control vectors for controlling a d-axis voltage command and a q-axis voltage command based on (a) a second d-axis current command value, which is calculated from a difference between a first d-axis current command value and a detected d-axis current value, (b) a second q-axis current command value which is calculated from a difference between a first q-axis current command value and a detected d-axis current value, (c) a frequency command value, and (d) motor constant settings; a motor constant identifying unit for identifying motor constants of the permanent magnet synchronous motor, by using the second d-axis current command value, the second q-axis current command value, a detected output current of the electric power converter, and the motor constant settings; wherein the vector control calculating unit uses the motor constants identified by the motor constant identifying unit in the vector control calculation of the vector control calculating unit so as to control driving of the permanent magnet synchronous motor; wherein, in a low-speed area in which the frequency command value is smaller than a value determined in advance, the motor constant identifying unit sets the first d-axis current command value to a prescribed value other than 0, and then multiplies a ratio of the second d-axis current command value to the detected d-axis current value by a resistance setting, which is one of the motor constant settings, so as to identify a resistance value of the motor.