Control device for rotating machine

A control device for a rotating machine, the control device comprising:

• a voltage applicator connected between a direct-current power supply and a rotating machine to apply a rectangular stator voltage to the rotating machine through on-off switching of a plurality of switching elements included for each of phases;
• a current detector to detect a stator current flowing between the voltage applicator and a stator winding of the rotating machine;
• processing circuitry
• to compute a voltage command value on a basis of the stator current and a rotor position serving as position information of a rotor of the rotating machine, the voltage command value being a command value for a stator voltage to be applied to the stator winding;
• to perform on-off control of the switching elements so that a smoothed value of the stator voltage matches the voltage command value;
• and
• to estimate, on a basis of the voltage command value and the stator current, the rotor position through a filter that removes a frequency component of a fundamental frequency of rotational speed of the rotating machine.