Hitachi, Ltd.

Junichi Takagi

Hideyuki Nakamura

Makoto Ishii

Noriaki Arakawa

Hideki Yoshida

Takeshi Wakatabe

Hideo Kumakura

A refrigerator, having a motor for driving a compressor, an inverter for controlling the operation of the motor, a converter responsive to AC to perform a boosting function to supply DC of variable voltage to the inverter, converter control means for controlling the converter so that a plurality of DC voltages are outputted thereby and inverter control means for controlling the inverter in pulse width modulation each of the plurality of voltages. The lowest voltage among the plurality of voltages being a voltage which turns off the boosting function of the converter.

Refrigerator

When inverter control is implemented in a refrigerator or the like, the rotating speed of a compressor motor is often operated at the preset minimum rotating speed. At this time, there has been a problem that when the DC voltage is boosted, the efficiency of the circuit drops due to switching loss in the power element. Still more, when the DC voltage is boosted even at the minimum rotating speed, the lowest voltage of the DC voltage must be controlled at 163 V or more including the fluctuation of the voltage. Therefore, there has been a problem in that the efficiency of the compressor motor also drops. To avoid these problems, when the temperature within a compartment of a refrigerator is cooled and approaches a preset temperature, and when a conduction ratio of the compressor motor falls below a preset value or a command on a rotating speed of the compressor motor becomes a preset rotating speed and the actual rotating speed also becomes the preset rotating speed, the control of the converter control circuit is turned off.

Growing community of inventors

Tochigi-ken, Japan

Junichi Takagi