Ac motor control apparatus

A control apparatus for controlling a three-phase AC motor, the control apparatus comprising:

• a current sensor configured to detect electric current flowing through one phase of the AC motor, the one phase being defined as a sensor phase;
• and
• a current estimation section configured to repeatedly perform a current estimation process in a predetermined cycle, wherein
• in the current estimation process, a d-axis current estimation value and a q-axis current estimation value in a rotating coordinate system of the AC motor are calculated based on a present current detection value of the sensor phase and a previous current estimation value of another phase of the AC motor, the present current detection value being defined as the current presently detected by the current sensor,
• in the current estimation process, a present current estimation value of each of the sensor phase and the other phase of the AC motor is calculated based on a smoothed d-axis current estimation value and a smoothed q-axis current estimation value into which the d-axis current estimation value and the q-axis current estimation value are respectively smoothed,
• the current estimation section performs the current estimation process based on a phase lag element of the sensor phase, and
• the phase lag element of the sensor phase is a difference between the present current detection value and one of a previous current estimation value of the sensor phase and a previous current detection value of the sensor phase, the previous current detection value being defined as the current previously detected by the current sensor.