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 both dq transformation and inverse dq transformation in a predetermined calculation cycle, wherein
• in the dq transformation, 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 the current detected by the current sensor and a previous current estimation value of another phase of the AC motor, and
• in the inverse dq transformation, a present current estimation value of the other phase to be obtained at a time of angle advance of one period of the calculation cycle 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.