Motor drive device

A motor drive device comprising:

• an inverter circuit that has a switching element provided corresponding to each phase of a motor having a motor coil of three phases, converts a DC voltage into an AC voltage by a PWM modulation associated with a switching operation of the switching element, and outputs the AC voltage to the motor coil of each phase;
• and
• a control device that controls the PWM modulation of the inverter circuit based on a control modulation factor value sampled at a predetermined period from a target modulation factor waveform determined in accordance with a target rotation number of the motor, and can selectively switch a scheme of the PWM modulation between a plurality of modulation schemes including a three-phase modulation scheme,
• wherein when the control device determines, based on the sampling number in one period of the target modulation factor waveform or a correlation value of the sampling number, that the sampling number is less than a predetermined value in a case where a modulation scheme other than the three-phase modulation scheme is selected and the target rotation number increases, the control device switches the scheme of the PWM modulation from the other modulation scheme to the three-phase modulation scheme.