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, of a sensor phase, which is one of three phases of the three-phase AC motor, the control apparatus comprising:

• an electric current estimation unit repeatedly performing at predetermined intervals an inverted dq conversion and a dq conversion for determining a d/q axis electric current estimate values in a rotation coordinate system of the AC motor, wherein
• the inverted dq conversion calculates an electric current estimate values for phases other than the sensor phase based on the d/q axis electric current estimate values of a previous cycle in the rotation coordinate system of the AC motor, and
• the dq conversion calculates the d/q axis electric current estimate values of a current cycle based on the electric current estimate values for the phases other than the sensor phase calculated by the inverted dq conversion and the electric current detection value of the sensor phase detected by the electric current detector.