Patent ID: 8415906

Claim:
A motor driving apparatus comprising: a PWM converter which, under PWM control, converts AC power supplied from a power source into DC power and vice versa; a PWM inverter which converts the DC power output from said PWM converter into variable-frequency AC power and vice versa, and which drives a motor with said variable-frequency AC power; a power storage device, provided between said PWM converter and said PWM inverter, that can store electric power in an amount capable of driving said motor; and a PWM converter control circuit which operates said PWM converter under PWM control, and wherein: said PWM converter control circuit causes the voltage of said power storage device to decrease by performing PWM control by gradually lowering a control target value of an output voltage of said PWM converter in corresponding relationship to motor output during the acceleration control period of said motor such that power less than the power required by said motor during an acceleration control period of said motor is supplied from said PWM converter and any deficit in power required to drive said motor is supplied from said power storage device; said PWM converter control circuit maintains the voltage of said power storage device by performing PWM control by setting a control target value of an output voltage of said PWM converter to the same value as the voltage at which said power storage device is to be maintained during the constant speed control period of said motor; and said PWM converter control circuit performs PWM control by gradually raising a control target value of an output voltage of said PWM converter in corresponding relationship to motor output during the deceleration period of said motor, so that at least a portion of the regenerative power occurring in said motor is recovered by said power storage device whose voltage has decreased, while not allowing said power storage device whose voltage has decreased to be charged from said power source and not allowing said regenerative power to pass through to said power source.