Control device for ac rotary machine and control device for electric power steering

A control device for an AC rotary machine, comprising:

• a DC power supply that outputs a DC voltage;
• an AC rotary machine having m sets of n-phase windings, where m is a natural number and n is a natural number no smaller than 3;
• a current detector that detects respective current values of the m sets of n-phase windings;
• a power converter that includes high potential side switching elements and low potential side switching elements, converts the DC voltage into an AC voltage in response to switching control implemented on the high potential side switching elements and the low potential side switching elements on the basis of ON/OFF signals, and applies the AC voltage to the windings;
• and
• a control unit that calculates voltage commands on the basis of respective differences between a current command for the AC rotary machine and current detection values obtained by the current detector, and outputs the ON/OFF signals to the high potential side switching elements and the low potential side switching elements of the power converter by comparing applied voltages calculated on the basis of the voltage commands with a carrier wave signal,
• wherein the current detector, when detecting currents flowing through the n-phase windings on the basis of currents flowing through current detection resistance elements that are inserted in series into the low potential side switching elements provided in the power converter for at least (n−1) phases, detects the currents at two or more fixed timings over a single period of the carrier wave signal to obtain current detection values that do not include errors caused by switching noise.