CONTROL DEVICE AND METHOD FOR AC ROTARY ELECTRICAL MACHINE, AND ELECTRICAL POWER STEERING DEVICE

Provided is a control device for an AC rotating machine, for controlling the AC rotating machine including a plurality of sets of windings. The control device includes: a plurality of inverters each including, in respective phases, switching elements for controlling voltages to be applied to respective phases of the windings; current control portion for issuing voltage commands corresponding to the voltages to the respective inverters to control currents flowing through the windings; and failure detection portion for detecting at least one of a short-circuit failure or an open-circuit failure in each of the switching elements. The current control portion sets, in accordance with the failure detected by the failure detection portion, the same potential side of the respective phases of a faulty-side inverter in the same state as in the detected failure, and continues control on a normal-side inverter except for the faulty-side inverter.