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 of three phases of the three-phase AC motor, the control apparatus comprising:

• an electric current estimation unit repeatedly performing, at a predetermined interval, an inverted dq conversion, a dq conversion, and a correction process, the electric current estimation unit 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 value of the sensor phase based on the d/q axis electric current estimate value of a previous cycle,
• the dq conversion calculates a d/q axis electric current correction values based on an electric current estimation error of the sensor phase, which is derived from the electric current estimate value of 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, and
• the correction process calculates the d/q axis electric current estimate values in the rotation coordinate system of the AC motor for a current cycle by correcting the d/q axis electric current estimate values of the previous cycle by using the d/q axis electric current correction values determined by the dq conversion.