Motor driver, heat pump system and refrigeration and air conditioning equipment using motor driver

A motor driving device comprising:

• an inverter used for driving a motor and configured to apply an alternating-current voltage to the motor, wherein
• the inverter drives, during start operation, a switching element of the inverter with a first PWM signal that is PWM modulated with a carrier frequency that is a first integer multiple of a frequency of the alternating-current voltage, and thereafter drives the switching element with a second PWM signal that is PWM modulated with a carrier frequency that is a second integer multiple of the frequency of the alternating-current voltage, the second integer being smaller than the first integer, and
• voltage output by the inverter is controlled so that a peak value of current flowing through the motor is constant while the current flowing through the motor is pulsed.

A motor driving device comprising:

• an inverter used for driving a motor and configured to apply an alternating-current voltage to the motor, wherein
• the inverter drives, during start operation, a switching element of the inverter with a first PWM signal that is PWM modulated with a carrier frequency that is a first integer multiple of a frequency of the alternating-current voltage, and thereafter drives the switching element with a second PWM signal that is PWM modulated with a carrier frequency that is a second integer multiple of the frequency of the alternating-current voltage, the second integer being smaller than the first integer, and
• voltage output by the inverter is controlled so that a peak value of current flowing through the motor is constant while rotation speed of the motor changes.