Ac motor control apparatus

A control apparatus of an alternate current (AC) motor, which includes a three-phase AC motor and an electric current detector for detecting an electric current, as an electric current detection value, in a sensor phase, which is one phase of the three-phase AC motor, the control apparatus comprising:

• an electric current estimation unit performing an electric current estimation process by calculating a d/q axis electric current estimate values in a rotation coordinate system of the AC motor and calculating an electric current estimate values of each phase of the AC motor, wherein
• the d/q axis electric current estimate values are based on the electric current detection value of the sensor phase detected by the electric current detector and on the electric current estimate values of phases other than the sensor phase from a previous cycle,
• the electric current estimate values of each phase of the AC motor are based on smoothed values derived from smoothing the d/q axis electric current estimate values, and
• during the calculation of the d/q axis electric current estimate values, the electric current estimation unit calculates the electric current estimate value of the sensor phase based on the d/q axis electric current estimate values of the previous cycle, and corrects the d/q axis electric current estimate values in a sensor phase orthogonal direction that is orthogonal to the sensor phase axis based on a sensor phase estimate error that is derived from the electric current estimate value of the sensor phase and the electric current detection value of the sensor phase detected by the electric current detector.