CONTROLLER FOR AC ROTARY MACHINE

To provide a controller for AC rotary machine which can detect current of the normal phase certainly when the short circuit failure of one phase occurs, in an apparatus that a current sensor is connected in series to the positive electrode side switching device or the negative electrode side switching device of an inverter. A controller for AC rotary machine, when determining that the short circuit failure of any one phase occurred, calculates voltage command values of normal n−1 phases, and changes the voltage command values of the normal n−1 phases so that on period of the detection object device of each phase of the normal n−1 phases become longer than or equal to a length necessary for current detection at least at a current detection timing.