To prevent a compressor from being shut off at all times irrespective of fluctuation of the deviation by forcibly setting the frequency of the AC output to be supplied to a compressor motor to a value to prevent the compressor motor from being stopped when the deviation data are judged to be not more than a prescribed value.
The AC output from an AC power source 1 is converted into the DC output by a converter circuit 2, and smoothed by a capacitor 3, and then, again converted into the AC output by an inverter circuit 4 to be supplied to a compressor motor 5. A compressor 6 is driven by the AC output supplied from the compressor motor 5. When it is judged that the deviation data obtained from the preset indoor temperature and the detected indoor temperature by a forcible frequency setting part 30 are not more than the prescribed value, the frequency of the AC output to be supplied to the compressor 5 is forcibly set to the value not to stop the compressor motor 5. The operating condition of the compressor can be always kept irrespective of the fluctuation of the deviation.
HIRAHARA MORIO
YAMASHITA TETSUJI
KAGEYAMA YASUHIRO
