Motor control method and motor control device

A motor control method for controlling a motor by transmitting a PWM signal at a predetermined carrier frequency to a power converter configured to supply power to the motor and performing switching control on the power converter, the method comprising:

• in a characteristic coordinate having a rotation speed of the motor and a torque of the motor as axes, the characteristic coordinate including a first region representing a region where the rotation speed is higher than a first predetermined rotation speed, a second region representing a region where the rotation speed is equal to or lower than the first predetermined rotation speed and the torque is higher than a predetermined torque, and a third region representing a region where the rotation speed is equal to or lower than the first predetermined rotation speed and the torque is equal to or lower than the predetermined torque,
• setting the carrier frequency to be a reference frequency when an operating point representing a current rotation speed and torque is included in the first region;
• selecting and setting the carrier frequency to be either the reference frequency or a low frequency lower than the reference frequency when the operating point is included in the second region;
• setting the carrier frequency to be the low frequency when the operating point is included in the third region;
• setting a modulation method of the PWM signal to be three-phase modulation when the operating point is included in a region other than a specific region disposed inside the third region;
• and
• setting the modulation method of the PWM signal to be two-phase modulation when the operating point is included in the specific region.