Apparatus for controlling rotating machine based on output signal of resolver

A control apparatus for controlling a rotating machine wherein a current flowing through the rotating machine is controlled by a DC-AC conversion circuit electrically connected thereto, the control apparatus comprising:

• a signal output unit that outputs an excitation signal to a resolver used for detecting a rotational angle of the rotating machine, the resolver generating a modulated signal where the excitation signal is amplitude-modulated in response to the rotational angle of the rotating machine;
• a demodulation unit that demodulates a signal related to the rotational angle based on a detection of the modulated signal and the excitation signal, and outputs a demodulated signal;
• a filter that eliminates higher harmonics in the demodulated signal outputted by the demodulation unit so as to output a calculated angle of the rotational angle, the filter having a cutoff region determined by a cutoff frequency thereof;
• an operating unit that controls a switching element included in the DC-AC conversion circuit to be ON and OFF based on the calculated angle of the rotational angle outputted by the filter, so as to control the rotating machine with an output voltage of the DC-AC conversion circuit supplied thereto;
• and
• a setting unit that sets an object frequency to be variable so as to have an error frequency, determined by a difference between a frequency of a variable component in the current flowing through the rotating machine and an frequency of the excitation signal, to be within the cutoff region of the filter, the object frequency being at least either an excitation frequency of the excitation signal or a switching frequency of the switching element.