| 摘要 |
PURPOSE:To maintain quietness and secure a stable operation at the time of manipulating a four-way change-over valve by forcibly holding a difference between high and low pressure of a coolant applied to the four-way change-over valve within a freezing circuit prior to stopping a compressor for a predetermined period of time regardless of the air conditioning load. CONSTITUTION:When a defrosting signal is inputted from a defrosting command apparatus 9, a microcomputer 13 while maintaining a space heating operation, actuates an inverter control circuit 8 so that a compressor motor 3 is driven by an AC of a frequency of 52Hz. Since the rotational speed of compressor motor 3 is lowered to that corresponding to 52Hz in an extremely short period of time, the difference between high and low pressures applied to the four-way valve 4 becomes stable at a predetermined value in the intermediate of a maximum ability time and a minimum ability time. Then, when a first set time passes, a step output is emitted and an electrically driven compressor 1 is stopped via a control circuit 8. Thereafter, when a second set time required for lowering the difference between high and low pressure to a proper value passes, the microcomputer 13 emits a changeover output to change over from th space heating side to the defrosting side, to the four-way changeover value 4.
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